I need to reverse vertex order in faces of my geometry.
In example:
// create geometry
var geometry = new THREE.Geometry();
// create vertices
geometry.vertices.push( new THREE.Vector3( 0, 0, 0 ) );
geometry.vertices.push( new THREE.Vector3( 0, 100, 0 ) );
geometry.vertices.push( new THREE.Vector3( 100, 0, 0 ) );
// create face
var face = new THREE.Face3( 0, 1, 2 );
geometry.faces.push ( face );
// compute normals
geometry.computeFaceNormals();
geometry.computeVertexNormals();
// add to scene
var mesh = new THREE.Mesh(
geometry,
new THREE.MeshBasicMaterial({color: 0x00ffff})
);
scene.add( mesh );
Now I need to change order of vertices in face from 0,1,2 to 2,1,0. But when I do this manually it does not work no matter which flags for update I set to true.
The question - is it possible to reverse vertices order on the fly and if yes then how?
Important - It's better to avoid using negative scale for geometry in this case. And it's also better to avoid re-creating of object.
THREE.js: r73
delete mesh.geometry.__directGeometry;
This should apply yours changes. In some reason in r72 and r73 __directGeometry not updated automatically.
Related
Any help from this great community would be such a blesing. I've recently been trying to figure out how to plot a set of points and faces that come from an XML file with Three.js.
The points look something like this:
<P id="1">472227.25640192 2943287.51179465 200.138787</P>
<P id="2">472232.14363148 2943288.56768013 200.129142</P>
<P id="3">472237.03086105 2943289.62356560 200.119496</P>
and the faces look like this:
<F>1021 1020 1061</F>
<F>640 754 641</F>
<F>1534 1633 1535</F>
Keep in mind that there are thousands of these faces and points and each of them has 3 numbers. I've converted to xml to json and done all the parsing required but when I try to do a sample of some of the points as lines in Three.js, I get nothing but a black screen. Here's what I tried. Is anything like I'm trying to do even possible with three.js? Is there a better alternative?
var renderer = new THREE.WebGLRenderer();
renderer.setSize( window.innerWidth, window.innerHeight );
document.body.appendChild( renderer.domElement );
var camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 500 );
camera.position.set( 0, 0, 100 );
camera.lookAt( 0, 0, 0 );
var scene = new THREE.Scene();
var material = new THREE.LineBasicMaterial( { color: 0x0000ff } );
var geometry = new THREE.Geometry();
geometry.vertices.push(new THREE.Vector3( 472227.25640192, 2943287.51179465, 200.138787) );
geometry.vertices.push(new THREE.Vector3( 472232.14363148, 2943288.56768013, 200.129142) );
geometry.vertices.push(new THREE.Vector3( 472237.03086105, 2943289.62356560, 200.119496) );
var line = new THREE.Line( geometry, material );
scene.add( line );
renderer.render( scene, camera );
Thanks, any help is appreciated.
The vertices you define are putting the line outside of the viewport. For example, change the coords to
geometry.vertices.push(new THREE.Vector3(1, 2, 0));
geometry.vertices.push(new THREE.Vector3(3, 3, 0));
geometry.vertices.push(new THREE.Vector3(5, 6, 0));
and you will see the line.
-or-
If the values you're working with are as large as the ones in your example, move the camera waaaaaay back on the z axis. (you could also scale the values to something more manageable)
I want to draw a triangle and i know only all angles (Alpha,Beta,Gamma) and all side length (10).
For drawing a triangle i need to set 3 vertices to geometry with absolute Vector3 values.
Is in THREE.js any integrated tool or practice fit for this?
geometry.vertices.push(
new THREE.Vector3( 0, 0, 0 ),
new THREE.Vector3( -10, -10, 0 ),
new THREE.Vector3( 10, -10, 0 ),
);
geometry.faces.push( new THREE.Face3( 0, 1, 2 ));
var material = new THREE.MeshBasicMaterial( { color: 0xffff00, side: THREE.DoubleSide } );
var mesh = new THREE.Mesh( geometry, material );
Only THREE method i can imagine is to create a 2 vector geometry with vector distance of side lengths, use matrix translation to set rotation pivot on vector[0] and change its position and rotation, each time set globalToWorld() for its vector[1]. But I think this is not a good solution.
I used this:
var length = 10;
var aplpha = 0.3;//rad
var beta= 1;//rad
geometry.vertices.push(
new THREE.Vector3(),
new THREE.Vector3(length ,0,0).applyAxisAngle(new THREE.Vector3(0,1,0),aplpha ),
new THREE.Vector3(length ,0,0).applyAxisAngle(new THREE.Vector3(0,1,0),beta ),
new THREE.Vector3(),
);
https://threejs.org/docs/#api/en/math/Vector3
THREE.JS r 96
Basicially I like to connect the right side of mesh 1 to the left side of mesh 2.
Currently, If I scale mesh1 I have to reposition mesh2 in order to have the same distance as before.
So let's scale mesh 1 to z: 2
var tween = new TWEEN.Tween(mesh1.scale).to({ z: 2 }, 1000).start();
tween.easing(TWEEN.Easing.Elastic.InOut);
In order to have the same distance to mesh 1 as before I have to reposition mesh 2 to z:1.5
var tween = new TWEEN.Tween(mesh2.position).to({ z: 1.5 }, 1000).start();
tween.easing(TWEEN.Easing.Elastic.InOut);
Are there any options in connecting the colored mesh faces. So If I scale mesh 1, mesh 2 automatically change it's position?
...
var geometry = new THREE.BoxGeometry( 1, 1, 1 );
var mesh1 = new THREE.Mesh( geometry,
new THREE.MeshPhongMaterial({color: 0x222222}));
mesh1 .position.set( 0, 0, 0 );
mesh1 .scale.set( 1, 1, 1 );
scene.add( mesh1 );
var mesh2 = new THREE.Mesh( geometry,
new THREE.MeshPhongMaterial({color: 0x222222}));
mesh2 .position.set( 0, 0, 1 );
mesh2 .scale.set( 1, 1, 1 );
scene.add( mesh2 );
This is a geometric problem.
I haven't worked with three.js before, but I believe I have a geometric solution.
Consider a third imaginary mesh, mesh3, such that it is a combination of mesh1 and mesh2.
That is:
mesh1: position(0, 0, 0), scale(1, 1, 1);
mesh2: position(0, 0, 1), scale(1, 1, 1);
mesh3: position(0, 0, 0), scale(1, 1, 2); // Loosely, mesh3 = mesh1 + mesh2
Now to scale the structure by a scalar k, I propose two approaches:
Approach 1:
Scale mesh1 and mesh3 each by k.
Compute the difference between mesh3 and mesh1, meshDiff.
Set mesh2 = meshDiff.
Approach 2:
Scale mesh3 by k.
Compute two halves of mesh3, mesh31 and mesh32, such that they are oriented along mesh1 and mesh2 respectively.
Set mesh1 = mesh31 and mesh2 = mesh32.
The approaches are very similar. Keep three.js's API in mind to choose the best approach.
Note: You needn't ever render mesh3. It only exists as a computational aid.
Generality:
The idea presented above can be used in other situations as well, wherein geometries sharing a common feature need to be scaled.
Hope this helps.
PS: I realize that this answer is a little abstract. Nonetheless, I hope it helps.
I used STLLoader to load an stl onto a threeJS scene returning a BufferGeometry.
I then used
myMesh.position.set( x,y,z )
myMesh.rotation.setFromQuaternion ( quaternion , 'XYZ');
to translate the geometry. This effectively changes the
myMesh.position
myMesh.quaternion
Translation is happening in the scene and all works well.
I expected that the
myMesh.geometry.attributes.position.array
would be different before and after the translation - but it remained identical. I want to extract the new veritces from the buffergeometry after translation.
I tried to call
myMesh.geometry.dynamic = true;
myMesh.geometry.attributes.position.needsUpdate = true;
in the render loop but no luck as I haven't updated the vertices explicity.
You want to get the world position of a mesh's geometry, taking into consideration the mesh's transform matrix, mesh.matrix. Also, your mesh geometry is THREE.BufferGeometry.
Here is the pattern to follow:
mesh = new THREE.Mesh( geometry, material );
mesh.position.set( 10, 10, 10 );
mesh.rotation.set( - Math.PI / 2, 0, 0 );
mesh.scale.set( 1, 1, 1 );
scene.add( mesh );
mesh.updateMatrix(); // make sure the mesh's matrix is updated
var vec = new THREE.Vector3();
var attribute = mesh.geometry.attributes.position; // we want the position data
var index = 1; // index is zero-based, so this the the 2nd vertex
vec.fromAttribute( attribute, index ); // extract the x,y,z coordinates
vec.applyMatrix4( mesh.matrix ); // apply the mesh's matrix transform
three.js r.71
I have a question about three.js.
How do I set an offset to a mesh?
The basic code is available at: http://lukas.achatz.ws/tst/webgl_003.html
What I want is to set a position offset and also that point should be used as the rotation reference.
I tried: mesh.applyMatrix( new THREE.Matrix4().makeTranslation( -2, 0, 0 ) ); but this only moves the mesh in the scene.
You can simply do:
var group = new THREE.Group();
scene.add( group );
var mesh = new THREE.Mesh( ..., ... );
mesh.position.set( -2, 0, 0 );
group.add( mesh );