Three.js has function called
THREE.Triangle() and I would like to know how to use it.
I suspect the Triangle class may not be what you are expecting it to be; it is not a class to be used directly for drawing simple 2D Triangles.
The Triangle class is a math utility function for encapsulating triangles and doing calculations, which is useful when drawing surfaces.
A good more detailed explanation for usage of triangles in drawing surfaces: Why are there always triangles used in a 3D engine?
If you are just trying to draw a simple 2D triangle:
var geom = new THREE.Geometry(); var v1 = new THREE.Vector3(0,0,0); var v2 = new THREE.Vector3(30,0,0); var v3 = new THREE.Vector3(30,30,0); geom.vertices.push(v1); geom.vertices.push(v2); geom.vertices.push(v3); geom.faces.push( new THREE.Face3( 0, 1, 2 ) ); geom.computeFaceNormals(); var mesh= new THREE.Mesh( geom, new THREE.MeshNormalMaterial() );
Another StackOverflow answer for this: Basic 2D colored triangle using three.js
Equivalent code using the Triangle class:
var geom = new THREE.Geometry(); var v1 = new THREE.Vector3(0,0,0); var v2 = new THREE.Vector3(30,0,0); var v3 = new THREE.Vector3(30,30,0); var triangle = new THREE.Triangle( v1, v2, v3 ); var normal = triangle.normal(); // An example of getting the area from the Triangle class console.log( 'Area of triangle is: '+ triangle.area() ); geom.vertices.push(triangle.a); geom.vertices.push(triangle.b); geom.vertices.push(triangle.c); geom.faces.push( new THREE.Face3( 0, 1, 2, normal ) );
jsbin link to play with: http://jsbin.com/zatejelika/1/edit?html,css,js,output
Triangle class documentation link: http://threejs.org/docs/#Reference/Math/Triangle