Im trying to build a simple 3d shape builder (it would always be a rectangle / square that needs to be built) all I want is for the user to be able enter the height, width and depth and the shape is built in real time for them as a line drawing. I have been looking online and found this jsfiddle which is great however I would need it to work in 3d (not just 2d) http://jsfiddle.net/m1erickson/f6E6Y/ but along those lines. Im however completly stuck and left scratching my head on this one...
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var width=2;
var height=35;
var $width=document.getElementById('width');
var $height=document.getElementById('height')
$width.value=width;
$height.value=height;
draw();
$width.addEventListener("keyup", function(){
width=this.value;
draw();
}, false);
$height.addEventListener("keyup", function(){
height=this.value;
draw();
}, false);
function draw(){
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.fillRect(40,40,width,height);
}
Any ideas?
Dealing with 3D is much easier with a library. Three.js is a popular one. They also have a demo for what you've described: http://threejs.org/docs/scenes/geometry-browser.html#BoxGeometry
The controls on the top-right will allow you to adjust the dimensions of the object in real-time. Modifying this example will be much more easier than writing it from scratch, unless you'd like to learn vanilla WebGL.
Related
There's a bunch of questions on panning a background image in a canvas (i.e. to simulate a 'camera' in a game with the character in the center) - and most answers suggest using the canvas' translate method.
But since you have to re-draw the image in each frame anyway, why not just clip it? Does it matter in terms of efficiency?
In particular, is panning like this a bad idea? (This example shows a simplified pan of the camera moving in one direction)
let drawing = new Image();
drawing.src = "img_src";
drawing.onload = function () {
ctx.drawImage(drawing, 0, 0);
let pos = 0
setInterval(() => {
pos += 1
ctx.clearRect(0, 0, cnvs.width, cnvs.height);
ctx.drawImage(drawing, -pos, 0 ); // "pans" the image to the left using the option `drawImage` parameters `sx` and `sy`
}, 33);
};
Example result: fiddle
Thanks in advance!
The main advantage of using the transform matrix to control your camera is that you don't have to update all the elements in your world, you just move the world instead.
So yes, if you are willing to move only a single element (be it the background like in your case), moving only that one element might be a better choice.
But if you need several layers of elements to all move relatively to the camera, then using the transformation matrix is a better choice.
As for the perfs, I didn't ran any benchmarks on this, but I'd suspect it's exactly the same, though beware when messing with the cropping features of drawImage, at least Safari doesn't handle cropping from outside of a source canvas correctly.
I'm two days into js,html and css programming. So very newbie!
Following and building upon this TUTORIAL
Q1: How can I add this male into the background (see figuere 1.) and prohibit any strokes outside of the borders?
Adding image to background was no biggy!
function make_base()
{
base_image = new Image();
base_image.src = 'img/bmapFront.gif';
base_image.onload = function(){
context.drawImage(base_image, 0,0);
}
}
There is a context.clip function, not sure if I can use pixel form as clipping path. Making tons of "image substractions" isn't the best way.
Any suggestions
Edit:
Did the Job for me: VeryHelpful
var frontPath = new Path2D ("M 133.41,17.00 C 141.37,2.41 160.66, !VERY LONG! ")
context.clip(frontPath);
Messy strokes!
He should look like this. Then I want to save him.
Although there is such a thing as ctx.clip(), this is sometimes not what's wanted as it's impractical to use a path.
The solution that I like involves creating a virtual empty canvas onto which you draw your pixel image. Through various manipulations, like using ctx.getImageData and similar to make sure you only get one kind of color or apply other filters only once, you can obtain an image that seems to be empty (alpha of 0, mostly) in the places where you want to clip other images or paths out.
At that point, you'd use ctx.globalCompositeOperation = 'source-atop', or pick another one you might want to use from mdn's list of globalCompositeOperations.
At this point, you can just draw this virtual canvas image onto the main canvas
So I have a semi-complex canvas drawing someone gave me. It draws an image vertically (i.e., top-down). Let's assume its a stick figure with facial features.
This is done in Javascript and Canvas. i.e.: ctx.beginPath(), ctx.moveTo(x,y), ctx.lineTo(1,1), etc.
I want the stick figure to move towards some point (x,y) and to face that direction while moving toward it. For example, if the x,y is near the bottom right, I want the stick figure to be oriented in a way such that its feet are facing towards the bottom right while it is moving.
The main question is, how would I go about doing this (i.e changing the stickman), knowing that I have a "hardcoded" drawing (in this example, stickman) that has been given to me?
You can render the received image on a separate canvas (doesn't need to be displayed) and use ctx.canvas.toDataURL() to convert it to an image. You could then embed the resulting image in your canvas and apply transforms to it more easily.
I mentioned this in a comment on the question but it sounded like fun, so I implemented a proof of concept.
var canvasObject = function(ctx) {
ctx.beginPath();
ctx.moveTo(0,0);
ctx.arc(30,30,15,0,2*Math.PI);
ctx.fillStyle='red';
ctx.fill();
return ctx;
}
var myCtx = document.querySelector('canvas').getContext('2d');
var objCtx = document.createElement('canvas').getContext('2d');
var renderedObjUrl = canvasObject(objCtx).canvas.toDataURL();
var renderedObj = document.createElement('img');
renderedObj.setAttribute('src', renderedObjUrl);
myCtx.drawImage(renderedObj, 30, 10);
<canvas id="myCanvas" width="600" height="400"></canvas>
I'm using JQueryKnob and trying to add segments to the radial. I'm not well versed in Canvas drawing, so that didn't seem like the best road to take - what I really need to do is just overlay a mask image on the drawn Knob canvas element. I've tried variations of this and it doesn't seem to work (I'm guessing the mask can't apply to canvases?)
I started to dabble with trying to just draw alpha'd lines in the JQueryKnob draw method, but didn't really have any luck with that either.
Any ideas? I'm pretty lost here
You're on the right track...just draw your masked image inside the draw method of your knob.
$(".knob").knob({
draw : function () {
var ctx=this.g;
var x=this.xy;
var y=this.xy;
var r=this.radius;
var iw=img.width;
var ih=img.height;
ctx.save();
ctx.beginPath();
ctx.arc(x,y,r,0,Math.PI*2);
ctx.clip();
ctx.drawImage( img, 0,0,iw,ih, x-iw/2,y-ih/2,iw,ih );
ctx.restore();
}
});
Here's example code and a Demo: https://jsfiddle.net/m1erickson/g8rx58hh/
I've been looking all day for a way to procedurally generate 2d texture with text in them so that I can apply them as a texture to a plane. Basically, I want to be able to change what text shows up in my WebGL page without having to just use texture made in an image editing program. I'm aiming to be able to edit the content of the page just as easily as with a totally 2d page, just edit the code and bam, it's there.
The most promising method I've seen to accomplish this is to render the text in a blank canvas with CSS, use that canvas as a texture which ThreeJS makes very easy, and then apply that texture to a plane that I can place wherever in the 3d environment.
I've attempted to accomplish this by adapting this example to my needs: http://jsfiddle.net/sSD65/28/
However, I end up with a totally black page, indicating an error somewhere. An error that I cannot, for the life of me, find and fix. I have a feeling I'm missing something because of my lack of experience with ThreeJS and in fact Javascript in general so I've come here to ask for your help.
I really appreciate any help I can get here.
Here's a link to the page, although I don't think you will be able to view it properly without hosting it locally since I'm loading an image from a folder there, but Python is wonderful for that. Just use Python -m SimpleHTTPServer in the console once you've navigated to that folder and it will host it locally so that you can access it from "http://localhost:8000/homepage.html": https://dl.dropbox.com/u/40043006/WebGLTest.zip
This is a simple code to add text from a canvas as a texture:
//create image
var bitmap = document.createElement('canvas');
var g = bitmap.getContext('2d');
bitmap.width = 100;
bitmap.height = 100;
g.font = 'Bold 20px Arial';
g.fillStyle = 'white';
g.fillText(text, 0, 20);
g.strokeStyle = 'black';
g.strokeText(text, 0, 20);
// canvas contents will be used for a texture
var texture = new THREE.Texture(bitmap)
texture.needsUpdate = true;
it needs some work... like setting the output text size to the canvas' size.