OpenGL Rotation Stop/Start Button

OpenGL Rotation Stop/Start Button - javascript

I need to create a start/stop button to start or stop the animation of a rotating square , I used a loop variable to decide if the square should rotate or not; in the render() function , if loop = 1 the square must rotate , if loop = 0 it stops. At the beginning loop=1 so the square is loaded in the html page rotating but the idea is that if I click the stop button it should stop , but it does not work.
Here is my code :
HTML
<!DOCTYPE html>
<html>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
uniform vec3 theta;
void main()
{
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
vec3 angles = radians( theta );
vec3 c = cos( angles );
vec3 s = sin( angles );
// Remeber: thse matrices are column-major
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, s.z, 0.0, 0.0,
-s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
fColor = vColor;
gl_Position = rz * ry * rx * vPosition;
gl_Position.z = -gl_Position.z;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void
main()
{
gl_FragColor = fColor;
}
</script>
<script type="text/javascript" src="../Common/webgl-utils.js"></script>
<script type="text/javascript" src="../Common/initShaders.js"></script>
<script type="text/javascript" src="../Common/MV.js"></script>
<script type="text/javascript" src="Exercise1_1.js"></script>
<body>
<canvas id="gl-canvas" width="512"" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
<br/>
<button id= "xButton">Rotate X</button>
<button id= "yButton">Rotate Y</button>
<button id= "zButton">Rotate Z</button>
<button id="StopButton">STOP ! </button>
</body>
</html>
JS
"use strict";
var canvas;
var gl;
var loop = 1;
var NumVertices = 36;
var points = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
colorCube();
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
//event listeners for buttons
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
document.getElementById("StopButton").onclick = function () {
loop = 0;
};
render();
}
function colorCube()
{
quad( 1, 0, 3, 2 );
quad( 2, 3, 7, 6 );
quad( 3, 0, 4, 7 );
quad( 6, 5, 1, 2 );
quad( 4, 5, 6, 7 );
quad( 5, 4, 0, 1 );
}
function quad(a, b, c, d)
{
var vertices = [
vec4( -0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, -0.5, -0.5, 1.0 ),
vec4( -0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, -0.5, -0.5, 1.0 )
];
var vertexColors = [
[ 0.0, 0.0, 0.0, 1.0 ], // black
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ], // green
[ 0.0, 0.0, 1.0, 1.0 ], // blue
[ 1.0, 0.0, 1.0, 1.0 ], // magenta
[ 0.0, 1.0, 1.0, 1.0 ], // cyan
[ 1.0, 1.0, 1.0, 1.0 ] // white
];
// We need to parition the quad into two triangles in order for
// WebGL to be able to render it. In this case, we create two
// triangles from the quad indices
//vertex color assigned by the index of the vertex
var indices = [ a, b, c, a, c, d ];
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
//colors.push( vertexColors[indices[i]] );
// for solid colored faces use
colors.push(vertexColors[a]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
if (loop = 0) {
theta[axis] = 0.0;
}
else {
theta[axis] +=2.0;
}
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}

Change
if (loop = 0)
To
if (loop == 0)
For a comparison in JavaScript you can use == or ===, the second option also checks the type. In your case both options can be used.
You used a single = which is used to assign a value to a variable.
If you want to stop rendering completely, you could rewrite your render function like this:
function render()
{
if (loop == 0) {
return;
}
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
theta[axis] += 2.0;
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}

Related

How to properly specify indices for a four-sided pyramid in WebGL?"

I am trying to create a 4-sided pyramid in WebGL where each face is a different color and I believe I'm running into issues with the indices. From my understanding, if I specify an indexed array, WebGL should be drawing a line between the corresponding vertices. I believe my code has all the necessary lines covered but I just can't get the pyramid to form correctly.
If someone could take a look at my code and help me figure out where I'm going wrong, that would be greatly appreciated!
Javascript code:
"use strict";
var canvas;
var gl;
var numPositions = 12;
var positions = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [0, 0, 0];
var thetaLoc;
window.onload = function init()
{
canvas = document.getElementById("gl-canvas");
gl = canvas.getContext('webgl2');
if (!gl) alert("WebGL 2.0 isn't available");
colorPyramid();
gl.viewport(0, 0, canvas.width, canvas.height);
gl.clearColor(1.0, 1.0, 1.0, 1.0);
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
var program = initShaders(gl, "vertex-shader", "fragment-shader");
gl.useProgram(program);
var cBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cBuffer);
gl.bufferData(gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW);
var colorLoc = gl.getAttribLocation( program, "aColor" );
gl.vertexAttribPointer( colorLoc, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( colorLoc );
var vBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vBuffer);
gl.bufferData(gl.ARRAY_BUFFER, flatten(positions), gl.STATIC_DRAW);
var positionLoc = gl.getAttribLocation(program, "aPosition");
gl.vertexAttribPointer(positionLoc, 4, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(positionLoc);
thetaLoc = gl.getUniformLocation(program, "uTheta");
//event listeners for buttons
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
render();
}
function colorPyramid()
{
triple(0, 3, 2); //base
triple(2, 0, 1);
triple(3, 1, 2);
triple(0, 1, 3);
}
function triple(a, b, c)
{
var vertices = [
vec3(0.5, -0.2722, 0.2886),
vec3(0.0, -0.2772, -0.5773),
vec3(-0.5, -0.2722, 0.2886),
vec3(0.0, 0.5443, 0.0)
];
var vertexColors = [
vec4(0.0, 0.0, 0.0, 1.0), // black
vec4(1.0, 0.0, 0.0, 1.0), // red
vec4(0.0, 1.0, 0.0, 1.0), // green
vec4(0.0, 0.0, 1.0, 1.0) // blue
];
// We need to parition the quad into two triangles in order for
// WebGL to be able to render it. In this case, we create two
// triangles from the quad indices
//vertex color assigned by the index of the vertex
var indices = [a, b, c];
for ( var i = 0; i < indices.length; ++i ) {
positions.push( vertices[indices[i]] );
//colors.push( vertexColors[indices[i]] );
// for solid colored faces use
colors.push(vertexColors[a]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
theta[axis] += 2.0;
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays(gl.TRIANGLES, 0, numPositions);
requestAnimationFrame(render);
}
I don't think the issue is my HTML code, but it never hurts to include it!
HTML:
<!DOCTYPE html>
<html>
<script id="vertex-shader" type="x-shader/x-vertex">
#version 300 es
in vec4 aPosition;
in vec4 aColor;
out vec4 vColor;
uniform vec3 uTheta;
void main()
{
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
vec3 angles = radians(uTheta);
vec3 c = cos(angles);
vec3 s = sin(angles);
// Remeber: thse matrices are column-major
mat4 rx = mat4(1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0);
mat4 ry = mat4(c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0);
mat4 rz = mat4(c.z, s.z, 0.0, 0.0,
-s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0);
vColor = aColor;
gl_Position = rz * ry * rx * aPosition;
gl_Position.z = -gl_Position.z;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
#version 300 es
precision mediump float;
in vec4 vColor;
out vec4 fColor;
void
main()
{
fColor = vColor;
}
</script>
<script type="text/javascript" src="http://interactivecomputergraphics.com/Code/Common/utility.js"></script>
<script type="text/javascript" src="http://interactivecomputergraphics.com/Code/Common/initShaders.js"></script>
<script type="text/javascript" src="http://interactivecomputergraphics.com/Code/Common/MV.js"></script>
<script type="text/javascript" src="ASPyramid.js"></script>
<body>
<canvas id="gl-canvas" width="512" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
<br/>
<button id= "xButton">Rotate X</button>
<button id= "yButton">Rotate Y</button>
<button id= "zButton">Rotate Z</button>
</body>
</html>

Ended up figuring out the issue with the help of a nice Redditor. I forgot to update the vertexAttribPointer for positionLoc to 3 instead of 4. The pyramid renders properly now.

Is there a way to have two images on a cube?

I'm trying to have two external images as textures for my cube. When I use one image, it works perfectly and my cube is rendered but I'm having problems rendering two images on one cube. One is a spotlight image that has the middle cut out so the second image placed can be seen through that hole. The only warning I get is
WebGL warning: generateMipmap: Tex image TEXTURE_2D level 0 is incurring lazy initialization.

When I try to run your code in Chrome 80 I get error messages in the JavaScript console
The first one is this
Uncaught TypeError: Failed to execute 'texImage2D' on 'WebGLRenderingContext': parameter 9 is not of type 'ArrayBufferView'.
at configureTexture1 (js:148)
You're trying to pass an HTMLImageElement to texImage2D but the only form of texImage2D that takes an HTMLImageElement has 6 parameters, not 9. No width, no height, and no border parameter. It should be
gl.texImage2D(
gl.TEXTURE_2D,
0, // level
gl.RGBA, // internal format
gl.RGBA, // format
gl.UNSIGNED_BYTE, // type
someImageElement);
Fixing those 2 errors leads to a new error
WARNING: there is no texture bound to the unit 1
When you use multiple textures you need to assign each texture to a texture unit. Example
// bind "someTexture" to texture unit 0
gl.activeTexture(gl.TEXTURE0 + 0);
gl.bindTexture(gl.TEXTURE_2D, someTexture);
// bind "otherTexture" to texture unit 1
gl.activeTexture(gl.TEXTURE0 + 1);
gl.bindTexture(gl.TEXTURE_2D, otherTexture);
var canvas;
var gl;
var numVertices = 36;
var texSize = 64;
var image1 = document.getElementById("texImage1");
var image2 = document.getElementById("texImage2");
var program;
var texture1, texture2;
var pointsArray = [];
var colorsArray = [];
var texCoordsArray = [];
//texture coordinates
var texCoord = [
vec2(0, 0),
vec2(0, 1),
vec2(1, 1),
vec2(1, 0)
];
//cube dimensions
var vertices = [
vec4( -0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, -0.5, -0.5, 1.0 ),
vec4( -0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, -0.5, -0.5, 1.0 )
];
var vertexColors = [
vec4( 0.0, 0.0, 0.0, 1.0 ),
vec4( 1.0, 0.0, 0.0, 1.0 ),
vec4( 1.0, 1.0, 0.0, 1.0 ),
vec4( 0.0, 1.0, 0.0, 1.0 ),
vec4( 0.0, 0.0, 1.0, 1.0 ),
vec4( 1.0, 0.0, 1.0, 1.0 ),
vec4( 0.0, 1.0, 1.0, 1.0 ),
vec4( 0.0, 1.0, 1.0, 1.0 )
];
//rotation parameters
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = xAxis;
var theta = [45.0, 45.0, 45.0];
var thetaLoc;
function configureTexture1( image ) {
texture1 = gl.createTexture();
gl.activeTexture( gl.TEXTURE0 + 0 );
gl.bindTexture( gl.TEXTURE_2D, texture1 );
gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image1);
gl.generateMipmap( gl.TEXTURE_2D );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER,gl.NEAREST_MIPMAP_LINEAR );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.uniform1i(gl.getUniformLocation( program, "texture1"), 0);
}
function configureTexture2( image ) {
texture2 = gl.createTexture();
gl.activeTexture( gl.TEXTURE0 + 1 );
gl.bindTexture( gl.TEXTURE_2D, texture2 );
gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image2);
gl.generateMipmap( gl.TEXTURE_2D );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER,gl.NEAREST_MIPMAP_LINEAR );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.uniform1i(gl.getUniformLocation( program, "texture2"), 1);
}
function quad(a, b, c, d) {
pointsArray.push(vertices[a]);
colorsArray.push(vertexColors[a]);
texCoordsArray.push(texCoord[0]);
pointsArray.push(vertices[b]);
colorsArray.push(vertexColors[a]);
texCoordsArray.push(texCoord[1]);
pointsArray.push(vertices[c]);
colorsArray.push(vertexColors[a]);
texCoordsArray.push(texCoord[2]);
pointsArray.push(vertices[a]);
colorsArray.push(vertexColors[a]);
texCoordsArray.push(texCoord[0]);
pointsArray.push(vertices[c]);
colorsArray.push(vertexColors[a]);
texCoordsArray.push(texCoord[2]);
pointsArray.push(vertices[d]);
colorsArray.push(vertexColors[a]);
texCoordsArray.push(texCoord[3]);
}
function colorCube()
{
quad( 1, 0, 3, 2 );
quad( 2, 3, 7, 6 );
quad( 3, 0, 4, 7 );
quad( 6, 5, 1, 2 );
quad( 4, 5, 6, 7 );
quad( 5, 4, 0, 1 );
}
window.onload = function init() {
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
colorCube();
//loading/initialising/binding buffers
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colorsArray), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer);
gl.bufferData( gl.ARRAY_BUFFER, flatten(pointsArray), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
var tBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, tBuffer);
gl.bufferData( gl.ARRAY_BUFFER, flatten(texCoordsArray), gl.STATIC_DRAW );
var vTexCoord = gl.getAttribLocation( program, "vTexCoord" );
gl.vertexAttribPointer( vTexCoord, 2, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vTexCoord );
configureTexture1(image1);
configureTexture2(image2);
thetaLoc = gl.getUniformLocation(program, "theta");
document.getElementById("ButtonX").onclick = function(){axis = xAxis;};
document.getElementById("ButtonY").onclick = function(){axis = yAxis;};
document.getElementById("ButtonZ").onclick = function(){axis = zAxis;};
render();
}
var render = function() {
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
theta[axis] += 2.0;
gl.uniform3fv(thetaLoc, flatten(theta));
gl.drawArrays( gl.TRIANGLES, 0, numVertices );
requestAnimFrame(render);
}
<button id = "ButtonX">Rotate X</button>
<button id = "ButtonY">Rotate Y</button>
<button id = "ButtonZ">Rotate Z</button>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
attribute vec2 vTexCoord;
varying vec4 fColor;
varying vec2 fTexCoord;
uniform vec3 theta;
void main()
{
vec3 angles = radians( theta );
vec3 c = cos( angles );
vec3 s = sin( angles );
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, s.z, 0.0, 0.0,
-s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
fColor = vColor;
fTexCoord = vTexCoord;
gl_Position = rz * ry * rx * vPosition;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
varying vec2 fTexCoord;
uniform sampler2D texture1;
uniform sampler2D texture2;
void
main()
{
gl_FragColor = fColor*(texture2D(texture1, fTexCoord)*texture2D(texture2, fTexCoord));
}
</script>
<script type="text/javascript"
src="https://esangel.github.io/WebGL/Common/webgl-utils.js"></script>
<script type="text/javascript" src="https://esangel.github.io/WebGL/Common/initShaders.js"></script>
<script type="text/javascript"
src="https://esangel.github.io/WebGL/Common/MV.js"></script>
<canvas id="gl-canvas" width="512" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
<img id="texImage1" crossorigin=" " src = "https://i.imgur.com/ZKMnXce.png" crossOrigin="anonymous" hidden></img>
<img id="texImage2" crossorigin=" " src = "https://i.imgur.com/aqZRuFj.png" crossOrigin="anonymous" hidden></img>
I used these 2 images
An F: https://i.imgur.com/ZKMnXce.png
A white dot: https://imgur.com/aqZRuFj
note that the code is not following normal WebGL practices. Many things are being done once at init time which will only work as long as you're onyl drawing a single thing.
See this answer and/or this page and this one too

Orthogonal projections using WebGL

I have to solve a task where is required to apply an orthogonal projection by using sliders or buttons to control the near and far plane of projection.
The object is a rotating cube. I've already defined many transformation functions , like rotation, scaling. It works, but when I tried to apply the model view matrix and the projection matrix it stops to work and the html does not show the cube.
The console said to me that there is a normalization problem of a NaN vector.
Here is my code :
HTML
<!DOCTYPE html>
<html>
<button id = "ButtonX">Rotate X</button>
<button id = "ButtonY">Rotate Y</button>
<button id = "ButtonZ">Rotate Z</button>
<button id = "ButtonT">Toggle Rotation</button>
<button id="Direction">Change Direction</button>
<div>Traslation on X -1 <input id="slideX" type="range"
min="-1" max="1" step="0.1" value="0" />
1 </div>
<div>Traslation on Y -1 <input id="slideY" type="range"
min="-1" max="1" step="0.1" value="0" />
1 </div>
<div>Traslation on Z -1 <input id="slideZ" type="range"
min="-1" max="1" step="0.1" value="0" />
1 </div>
<div>Scaling on X -1 <input id="ScalingX" type="range"
min="0" max="1" step="0.1" value="0" />
1 </div>
<div>Scaling on Y -1 <input id="ScalingY" type="range"
min="0" max="1" step="0.1" value="0" />
1 </div>
<div>Scaling on Z -1 <input id="ScalingZ" type="range"
min="0" max="1" step="0.1" value="0" />
1 </div>
<button id="Button1">Increase Z</button>
<button id="Button2">Decrease Z</button>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
//uniform vec3 theta;
// Point 2 -> Move the matrices
// Per spostare le matrici le abbiamo dovuto dichiarare nel file GLSL come uniform
// le matrici rx ry e rz sono rispettivamente le matrici di rotazione sugli assi
uniform mat4 rx;
uniform mat4 ry;
uniform mat4 rz;
// Points 3 -> Traslation Matrix
uniform mat4 traslation;
// Points 3 -> Scaling Matrix
uniform mat4 scaling;
//Point 4 -> MV and P matrices
uniform mat4 modelView;
uniform mat4 projection;
void main()
{
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
//vec3 angles = radians( theta );
//vec3 c = cos( angles );
//vec3 s = sin( angles );
// Remember: the matrices are column-major
/*
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, s.z, 0.0, 0.0,
-s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
*/
fColor = vColor;
gl_Position = scaling *rz * ry * rx * traslation * vPosition ; // ORDINE : scaling -> rotazione -> traslation
//gl_Position = scaling *rz * ry * rx * traslation *projection*modelView*vPosition ;
gl_Position.z = -gl_Position.z;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void
main()
{
gl_FragColor = fColor;
}
</script>
<script type="text/javascript" src="../Common/webgl-utils.js"></script>
<script type="text/javascript" src="../Common/initShaders.js"></script>
<script type="text/javascript" src="../Common/MV.js"></script>
<script type="text/javascript" src="Homework1.js"></script>
<body>
<canvas id="gl-canvas" width="1024" height="1024">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
</body>
</html>
JS
"use strict";
var canvas;
var gl;
var numVertices = 36;
var numChecks = 8;
var program;
var c;
var flag = true;
var direction = true;
var rx;
var ry;
var rz;
var traslation_loc;
var tx = 0 ;
var ty = 0;
var tz = 0;
var scaling_loc;
var sx = 1.0;
var sy = 1.0;
var sz = 1.0;
var pointsArray = [];
var colorsArray = [];
//Point 4
var near = -1;
var far = 1;
var radius = 1.0;
var theta = 0.0;
var phi = 0.0;
var dr = 5.0 * Math.PI/180.0;
var left = -1.0;
var right = 1.0;
var ytop = 1.0;
var bottom = -1.0;
var mvMatrix, pMatrix;
var modelView, projection;
var eye;
const at = vec3(0.0, 0.0, 0.0);
const up = vec3(0.0, 1.0, 0.0);
//
var vertices = [
vec4( -0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, -0.5, -0.5, 1.0 ),
vec4( -0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, -0.5, -0.5, 1.0 )
];
var vertexColors = [
vec4( 0.0, 0.0, 0.0, 1.0 ), // black
vec4( 1.0, 0.0, 0.0, 1.0 ), // red
vec4( 1.0, 1.0, 0.0, 1.0 ), // yellow
vec4( 0.0, 1.0, 0.0, 1.0 ), // green
vec4( 0.0, 0.0, 1.0, 1.0 ), // blue
vec4( 1.0, 0.0, 1.0, 1.0 ), // magenta
vec4( 0.0, 1.0, 1.0, 1.0 ), // white
vec4( 0.0, 1.0, 1.0, 1.0 ) // cyan
];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = xAxis;
var theta = [45.0, 45.0, 45.0];
//var thetaLoc;
function quad(a, b, c, d) {
pointsArray.push(vertices[a]);
colorsArray.push(vertexColors[a]);
pointsArray.push(vertices[b]);
colorsArray.push(vertexColors[a]);
pointsArray.push(vertices[c]);
colorsArray.push(vertexColors[a]);
pointsArray.push(vertices[a]);
colorsArray.push(vertexColors[a]);
pointsArray.push(vertices[c]);
colorsArray.push(vertexColors[a]);
pointsArray.push(vertices[d]);
colorsArray.push(vertexColors[a]);
}
function colorCube()
{
quad( 1, 0, 3, 2 );
quad( 2, 3, 7, 6 );
quad( 3, 0, 4, 7 );
quad( 6, 5, 1, 2 );
quad( 4, 5, 6, 7 );
quad( 5, 4, 0, 1 );
}
window.onload = function init() {
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
colorCube();
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colorsArray), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer);
gl.bufferData( gl.ARRAY_BUFFER, flatten(pointsArray), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
// Possiamo commentare quello che riguarda il theta per il punto 2
//thetaLoc = gl.getUniformLocation(program, "theta");
// Point 2 - Rotation
//X AXIS
rx = gl.getUniformLocation(program, "rx");
//Y AXIS
ry = gl.getUniformLocation(program, "ry");
//Z AXIS
rz = gl.getUniformLocation(program, "rz");
// Traslation Matrix
traslation_loc = gl.getUniformLocation(program , "traslation");
// Scaling Matrix
scaling_loc = gl.getUniformLocation(program , "scaling");
// Projection and Model matrix
modelView = gl.getUniformLocation( program, "modelView" );
projection = gl.getUniformLocation( program, "projection" );
//**************
document.getElementById("ButtonX").onclick = function(){axis = xAxis;};
document.getElementById("ButtonY").onclick = function(){axis = yAxis;};
document.getElementById("ButtonZ").onclick = function(){axis = zAxis;};
document.getElementById("ButtonT").onclick = function(){flag = !flag;};
document.getElementById("Direction").onclick = function() { direction = !direction;};
document.getElementById( "slideX" ).oninput = function(){ tx = parseFloat(event.target.value,10); };
document.getElementById( "slideY" ).oninput = function(){ ty = parseFloat(event.target.value,10); };
document.getElementById( "slideZ" ).oninput = function(){ tz = parseFloat(event.target.value,10); };
document.getElementById( "ScalingX" ).oninput = function(){ sx = parseFloat(event.target.value,10); };
document.getElementById( "ScalingY" ).oninput = function(){ sy = parseFloat(event.target.value,10); };
document.getElementById( "ScalingZ" ).oninput = function(){ sz = parseFloat(event.target.value,10); };
// Point 4
document.getElementById("Button1").onclick = function(){near *= 1.1; far *= 1.1;};
document.getElementById("Button2").onclick = function(){near *= 0.9; far *= 0.9;};
render();
}
var render = function() {
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Point 4
//*************************************
eye = vec3(radius*Math.sin(phi), radius*Math.sin(theta),
radius*Math.cos(phi));
mvMatrix = lookAt(eye, at , up);
pMatrix = ortho(left, right, bottom, ytop, near, far);
gl.uniformMatrix4fv( modelView, false, flatten(mvMatrix) );
gl.uniformMatrix4fv( projection, false, flatten(pMatrix) );
//*************************************
// Point 3 -> Scaling
var scaling = [sx , 0.0 , 0.0 , 0.0,
0.0 , sy, 0.0 , 0.0,
0.0 , 0.0 , sz , 0.0,
0.0 , 0.0 , 0.0 , 1];
gl.uniformMatrix4fv(scaling_loc,false,scaling);
// ****************************************
//X AXIS - Point 2
var theta_x_degree = theta[0];
var theta_x_radians = theta_x_degree * Math.PI / 180;
var s_x = Math.sin(theta_x_radians);
var c_x = Math.cos(theta_x_radians);
var rx_loc = [ 1.0, 0.0, 0.0, 0.0,
0.0, c_x, s_x, 0.0,
0.0, -s_x, c_x, 0.0,
0.0, 0.0, 0.0, 1.0 ];
gl.uniformMatrix4fv(rx, false, rx_loc);
//Y AXIS - Point 2
var theta_y_degree = theta[1];
var theta_y_radians = theta_y_degree * Math.PI / 180;
var s_y = Math.sin(theta_y_radians);
var c_y = Math.cos(theta_y_radians);
var ry_loc = [ c_y, 0.0, -s_y, 0.0,
0.0, 1.0, 0.0, 0.0,
s_y, 0.0, c_y, 0.0,
0.0, 0.0, 0.0, 1.0 ];
gl.uniformMatrix4fv(ry, false, ry_loc);
//Z AXIS - Point 2
var theta_z_degree = theta[2];
var theta_z_radians = theta_z_degree * Math.PI / 180;
var s_z = Math.sin(theta_z_radians);
var c_z = Math.cos(theta_z_radians);
var rz_loc = [ c_z, s_z, 0.0, 0.0,
-s_z, c_z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 ];
gl.uniformMatrix4fv(rz, false, rz_loc);
// ****************************************
// Point 3 -> Traslation
var traslation = [1.0 , 0.0 , 0.0 , 0.0,
0.0 , 1.0 , 0.0 , 0.0,
0.0 , 0.0 , 1.0 , 0.0,
tx , ty , tz , 1.0];
gl.uniformMatrix4fv(traslation_loc,false,traslation);
// ****************************************
// ****************************************
// Point 1 --> Change and Toggle Rotation
if((direction)&&(!flag)) theta[axis] += -2.0;
if((!direction)&&(!flag)) theta[axis] += +2.0;
if(!direction) {theta[axis] += -2.0; }
if(direction) {theta[axis] += 2.0 ; }
// ****************************************
//gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, numVertices );
requestAnimFrame(render);
}

I found the problem , it was the initialization of the var "eye" . There was a "0" that can not be computed.

Slider to rotate a square

I have to use a slider to change the angle of my rotating square :
JS
"use strict";
var canvas;
var gl;
var direction = true;
var degrees = 0;
var NumVertices = 36;
var points = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
colorCube();
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
//event listeners for buttons
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
// Start or Stop
var btn = document.getElementsByTagName('input')[0];
btn.addEventListener('click', function() {
if (direction == true)
direction = false;
else
direction = true;
});
// SLIDER
document.getElementById("slide").onchange = function(){
degrees = parseInt(event.target.value, 10);
};
render();
}
function colorCube()
{
quad( 1, 0, 3, 2 );
quad( 2, 3, 7, 6 );
quad( 3, 0, 4, 7 );
quad( 6, 5, 1, 2 );
quad( 4, 5, 6, 7 );
quad( 5, 4, 0, 1 );
}
function quad(a, b, c, d)
{
var vertices = [
vec4( -0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, -0.5, -0.5, 1.0 ),
vec4( -0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, -0.5, -0.5, 1.0 )
];
var vertexColors = [
[ 0.0, 0.0, 0.0, 1.0 ], // black
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ], // green
[ 0.0, 0.0, 1.0, 1.0 ], // blue
[ 1.0, 0.0, 1.0, 1.0 ], // magenta
[ 0.0, 1.0, 1.0, 1.0 ], // cyan
[ 1.0, 1.0, 1.0, 1.0 ] // white
];
// We need to parition the quad into two triangles in order for
// WebGL to be able to render it. In this case, we create two
// triangles from the quad indices
//vertex color assigned by the index of the vertex
var indices = [ a, b, c, a, c, d ];
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
//colors.push( vertexColors[indices[i]] );
// for solid colored faces use
colors.push(vertexColors[a]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
if (direction == false){
theta[axis] == degrees;
//theta[axis] = degrees;
}
else {
theta[axis] += 2.0;
}
/// How to control the rotation degree ?
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}
HTML
<!DOCTYPE html>
<html>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
uniform vec3 theta;
void main()
{
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
vec3 angles = radians( theta );
vec3 c = cos( angles );
vec3 s = sin( angles );
// Remeber: thse matrices are column-major
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, s.z, 0.0, 0.0,
-s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
fColor = vColor;
gl_Position = rz * ry * rx * vPosition;
gl_Position.z = -gl_Position.z;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void
main()
{
gl_FragColor = fColor;
}
</script>
<script type="text/javascript" src="../Common/webgl-utils.js"></script>
<script type="text/javascript" src="../Common/initShaders.js"></script>
<script type="text/javascript" src="../Common/MV.js"></script>
<script type="text/javascript" src="Exercise1_1.js"></script>
<body>
<canvas id="gl-canvas" width="512"" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
<br/>
<button id= "xButton">Rotate X</button>
<button id= "yButton">Rotate Y</button>
<button id= "zButton">Rotate Z</button>
<input type="button" value="Start or Stop" />
<div>
Angle 0 <input id="slide" type="range"
min="0" max="10" step="1" value="1" />
10 </div>
</body>
</html>
This square must stop when I click the button and restart the rotation if I click it again and this task works. The problem is that I have to change the angle using the slider and it works too if I remove the comment in the last if statement.
The problem is that if I click the start button and then I stop it , it stops in the beginning position and not in the last/current position (this happens if I remove the comment from the if statement code , if I leave the comment the start/stop works well but I can not change the angle).
Thanks for the help.

Fist of all, this line is wrong theta[axis] == degrees;
As you can see you have 2x = so you compare the theta[axis] with the degrees. This means that this line does nothing.
You want to stop the movement of the cube if the button is pressed and start it if it is pressed again, so thats why you have the variable direction.
If the direction is true, then you cube must move, so your theta[axis] should increase. If your direction is false your cube should stay still, so theta[axis] must keep its value.
So something like this:
// If cube is moving
if (direction == true) {
theta[axis] += 2.0;
}
// If no movement
else {
// Do nothing
// the theta[axis] stays the same
}
But now your cube is rotating with the same speed...
Maybe you want your cube to rotate with the degrees speed.
So you should change the static value of 2.0 to the variable degrees
that gets its value from the slider.
"use strict";
var canvas;
var gl;
var direction = true;
var degrees = 1.0; // Slider starts from value 1.0 as it has value="1" on it
var NumVertices = 36;
var points = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
colorCube();
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
//event listeners for buttons
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
// Start or Stop
var btn = document.getElementsByTagName('input')[0];
btn.addEventListener('click', function() {
if (direction == true)
direction = false;
else
direction = true;
});
// SLIDER
document.getElementById("slide").onchange = function(){
// As this is an event of the slider,
// here inside the handler, the variable `this`
// points to the slider, so we can do `this.value`
// to get the slider's value
degrees = parseInt(this.value, 10);
};
render();
}
function colorCube()
{
quad( 1, 0, 3, 2 );
quad( 2, 3, 7, 6 );
quad( 3, 0, 4, 7 );
quad( 6, 5, 1, 2 );
quad( 4, 5, 6, 7 );
quad( 5, 4, 0, 1 );
}
function quad(a, b, c, d)
{
var vertices = [
vec4( -0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, -0.5, -0.5, 1.0 ),
vec4( -0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, -0.5, -0.5, 1.0 )
];
var vertexColors = [
[ 0.0, 0.0, 0.0, 1.0 ], // black
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ], // green
[ 0.0, 0.0, 1.0, 1.0 ], // blue
[ 1.0, 0.0, 1.0, 1.0 ], // magenta
[ 0.0, 1.0, 1.0, 1.0 ], // cyan
[ 1.0, 1.0, 1.0, 1.0 ] // white
];
// We need to parition the quad into two triangles in order for
// WebGL to be able to render it. In this case, we create two
// triangles from the quad indices
//vertex color assigned by the index of the vertex
var indices = [ a, b, c, a, c, d ];
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
//colors.push( vertexColors[indices[i]] );
// for solid colored faces use
colors.push(vertexColors[a]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
if (direction != false){
theta[axis] += degrees;
// theta[axis] is increased by the degrees variable
// that is being updated with the value of the slider
// every time we slide the slider
}
// How to control the rotation degree ?
// With a nice slider! ...
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}

WebGL Vertex Shader fails to compile and 'WebGLRenderingContext :' parameter 1 is not of type 'WebGLProgram'

When I try to run the code below in my browser I receive a pop-up notification that "Vertex shader failed to compile. The error log is:
<pre>ERROR: 0:11: 'assign' : cannot convert from 'highp 3-component vector of float' to 'Position highp 4-component vector of float'
</pre>
Followed by the console error message:
"Uncaught TypeError: Failed to execute 'useProgram' on 'WebGLRenderingContext': parameter 1 is not of type 'WebGLProgram'.init # tangram2.js:76"
I am trying to create several 2-D shapes (just one for now, as a proof of concept), each with their own buffer, so that I may translate and rotate them on the GPU individually.
"use strict";`
var canvas, gl, program;
var points = [];
var colors = [];
var shapeScale = (1/3);
/* RGBA colors */
var vertexColors = [
vec4( 0.0, 0.0, 0.0, 1.0 ), // black
vec4( 1.0, 0.0, 0.0, 1.0 ), // red
vec4( 1.0, 1.0, 0.0, 1.0 ), // yellow
vec4( 0.0, 1.0, 0.0, 1.0 ), // green
vec4( 0.0, 0.0, 1.0, 1.0 ), // blue
vec4( 1.0, 0.0, 1.0, 1.0 ), // magenta
vec4( 1.0, 1.0, 1.0, 1.0 ), // white
vec4( 0.0, 1.0, 1.0, 1.0 ) // cyan
];
/* Shader transformation matrices */
var modelViewMatrix, projectionMatrix;
/* Rotational indicies */
var LT1 = 0; /* Large triangle 01 */
var LT2 = 1; /* Large triangle 02 */
var MT1 = 2; /* Medium triangle 01 */
var ST1 = 3; /* Small triangle 01 */
var ST2 = 4; /* Small triangle 02 */
var SQR = 5; /* Square */
var PRL = 6; /* Parallelogram */
var theta = [0,0,0,0,0,0,0];
var modelViewMatrixLoc;
/* For each shape, create a vertex and color buffer */
var vLT1Buff, cLT1Buff;
var vLT2Buff, cLT2Buff;
var vMT1Buff, cMT1Buff;
var vST1Buff, cST1Buff;
var vST2Buff, cST2Buff;
var vSQRBuff, cSQRBuff;
var vPRLBuff, cPRLBuff;
/* ----------------Initialize webGL---------------- */
window.onload = function init(){
/* From robotArm.js */
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable( gl.DEPTH_TEST );
/* Setup canvas background */
gl.viewport(0, 0, canvas.width, canvas.height);
gl.clearColor(1.0, 0.5, 0.5, 1.0);
/* Load shaders and use the resulting shader program */
program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
/* Create an initialize buffer objects */
vLT1Buff = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vLT1Buff );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
cLT1Buff = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cLT1Buff );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
modelViewMatrixLoc = gl.getUniformLocation(program, "modelViewMatrix");
projectionMatrix = ortho(-10, 10, -10, 10, -10, 10);
gl.uniformMatrix3fv( gl.getUniformLocation(program, "projectionMatrix"), false, flatten(projectionMatrix) );
//-------------------------------------//
// Initialize Shapes //
//-------------------------------------//
var largeTriangle01 = setupTriangle( 1, Math.sqrt(2) / 2);
var largeTriangle02 = setupTriangle( 1, Math.sqrt(2) / 2);
var medTriangle01 = setupTriangle( Math.sqrt(2) / 2, 0.35);
var smallTriangle01 = setupTriangle( 0.5, 0.25);
var smallTriangle02 = setupTriangle( 0.5, 0.25);
/* Add our shapes to an array of shapes for quick access */
var shapes = [
largeTriangle01,
/*
largeTriangle02,
medTriangle01,
smallTriangle01,
smallTriangle02,
square01,
*/
];
for(var i = 0; i < shapes.length; ++i){
scaleShape( shapes[i] ); //Scale our shapes
makeShape ( shapes[i] ); //And draw them
}
render(LT1);
}//end init
/* ----------------Helper funcitons---------------- */
//TODO dont forget about Parallelogram!
/* From robotArm.js */
function scale3(a, b) {
var result = mat3();
result[0][0] = a;
result[1][1] = b;
return result;
}
/* Return an array of three points representing a triangle */
function setupTriangle(hypotenuse, height){
return [
vec4( hypotenuse / 2, height, 0.0, 1.0 ),
vec4( hypotenuse , 0, 0.0, 1.0 ),
vec4( 0, 0, 0.0, 1.0 ),
];
}//end setupTriangle
/* Return an array of four points representing a quad */
function setupRectangle(width, height){
return[
vec4( -width, height, 0.0, 1.0),
vec4( width, height, 0.0, 1.0),
vec4( width, -height, 0.0, 1.0),
vec4( -width, -height, 0.0, 1.0),
];
}//end setupRectangle
function scaleShape(shape){
for( var i = 0; i < shape.length; ++i ){
shape[i] = scale( shapeScale, shape[i] );
}
}//end scaleShape
function makeShape(shape){
if(shape.length == 3){ makeTriangle (shape); }
if(shape.length == 4){ makeQuad (shape); }
}//end makeShape
function makeTriangle(listOfPoints){
for(var i = 0; i < listOfPoints.length; ++i){
points.push(listOfPoints[i]);
}
}//end makeShape
function makeQuad(listOfPoints){
points.push( listOfPoints[0] );
points.push( listOfPoints[1] );
points.push( listOfPoints[2] );
points.push( listOfPoints[0] );
points.push( listOfPoints[2] );
points.push( listOfPoints[3] );
}//end makeShape
/* ------------------------------------------------------------------------- */
function largeTriangle01(){
// var s = scale3(1.0, 1.0, 1.0);
var instanceMatrix = translate(0.5, 0.5);
var t = mult(modelViewMatrix, instanceMatrix);
gl.uniformMatrix3fv(modelViewMatrixLoc, false, flatten(t) );
gl.drawArrays( gl.TRIANGLES, 0, points.length );
}
/* ------------------------------------------------------------------------- */
function render(shape){
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
modelViewMatrix = rotate(theta[shape], 0, 1, 0);
switch(shape){
/* Large Triangle 01 */
case 0:
largeTriangle01();
break;
}//end switch
requestAnimFrame(render);
}//end render
My shaders are:
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec3 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
uniform mat3 modelViewMatrix;
uniform mat3 projectionMatrix;
void main() {
fColor = vColor;
gl_Position = projectionMatrix * modelViewMatrix * vPosition;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void main() {
gl_FragColor = fColor;
}
</script>

As #Reto said,
the error message tells you exactly what the problem is. You're trying to assign a vec3 to gl_Position, which is a vec4
It even tells you the line number: ERROR: 0:11 line 11
If we number the lines
<script id="vertex-shader" type="x-shader/x-vertex">1
2 attribute vec3 vPosition;
3 attribute vec4 vColor;
4 varying vec4 fColor;
5
6 uniform mat3 modelViewMatrix;
7 uniform mat3 projectionMatrix;
8
9 void main() {
10 fColor = vColor;
11 gl_Position = projectionMatrix * modelViewMatrix * vPosition;
12 }
</script>
I'm guessing you want
gl_Position = vec4(projectionMatrix * modelViewMatrix * vPosition, 1);

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