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Hey 👋

Welcome to WebGL month.

In previous tutorials we've been rendering only a signle object, but typical 3D scene consists of a multiple objects.

Today we're going to learn how to render many objects on scene.

Since we're rendering objects with a solid color, let's get rid of colorIndex attribute and pass a signle color via uniform

📄 src/3d.js



const { vertices, normals } = parseObj(monkeyObj); - const faceColors = [ - [0.5, 0.5, 0.5, 1.0] - ]; - - const colors = []; - - for (var j = 0; j < vertices.length / 3; ++j) { - colors.push(0, 0, 0, 0); - } - - faceColors.forEach((color, index) => { - gl.uniform4fv(programInfo.uniformLocations[`colors[${index}]`], color); - }); + gl.uniform3fv(programInfo.uniformLocations.color, [0.5, 0.5, 0.5]); const vertexBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW); - const colorsBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW); const normalsBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, normals, gl.STATIC_DRAW); vertexBuffer.bind(gl); gl.vertexAttribPointer(programInfo.attributeLocations.position, 3, gl.FLOAT, false, 0, 0); - colorsBuffer.bind(gl); - gl.vertexAttribPointer(programInfo.attributeLocations.colorIndex, 1, gl.FLOAT, false, 0, 0); - normalsBuffer.bind(gl); gl.vertexAttribPointer(programInfo.attributeLocations.normal, 3, gl.FLOAT, false, 0, 0);

📄 src/shaders/3d.v.glsl



attribute vec3 position; attribute vec3 normal; - attribute float colorIndex; uniform mat4 modelMatrix; uniform mat4 viewMatrix; uniform mat4 projectionMatrix; uniform mat4 normalMatrix; - uniform vec4 colors[6]; + uniform vec3 color; uniform vec3 directionalLightVector; varying vec4 vColor; vec3 transformedNormal = (normalMatrix * vec4(normal, 1.0)).xyz; float intensity = dot(transformedNormal, normalize(directionalLightVector)); - vColor.rgb = vec3(0.3, 0.3, 0.3) + colors[int(colorIndex)].rgb * intensity; + vColor.rgb = vec3(0.3, 0.3, 0.3) + color * intensity; vColor.a = 1.0; }

We'll need a helper class to store object related info

📄 src/Object3D.js



export class Object3D { constructor () { } }

Each object should contain it's own vertices and normals

📄 src/Object3D.js



+ import { parseObj } from "./gl-helpers"; + export class Object3D { - constructor() { - - } + constructor(source) { + const { vertices, normals } = parseObj(source); + + this.vertices = vertices; + this.normals = normals; + } }

As well as a model matrix to store object transform

📄 src/Object3D.js



import { parseObj } from "./gl-helpers"; + import { mat4 } from "gl-matrix"; export class Object3D { constructor(source) { this.vertices = vertices; this.normals = normals; + + this.modelMatrix = mat4.create(); } }

Since normal matrix is computable from model matrix it makes sense to define a getter

📄 src/Object3D.js



this.normals = normals; this.modelMatrix = mat4.create(); + this._normalMatrix = mat4.create(); + } + + get normalMatrix () { + mat4.invert(this._normalMatrix, this.modelMatrix); + mat4.transpose(this._normalMatrix, this._normalMatrix); + + return this._normalMatrix; } }

Now we can refactor our code and use new helper class

📄 src/3d.js



import { compileShader, setupShaderInput, parseObj } from './gl-helpers'; import { GLBuffer } from './GLBuffer'; import monkeyObj from '../assets/objects/monkey.obj'; + import { Object3D } from './Object3D'; const canvas = document.querySelector('canvas'); const gl = canvas.getContext('webgl'); const programInfo = setupShaderInput(gl, program, vShaderSource, fShaderSource); - const { vertices, normals } = parseObj(monkeyObj); + const monkey = new Object3D(monkeyObj); gl.uniform3fv(programInfo.uniformLocations.color, [0.5, 0.5, 0.5]); - const vertexBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW); - const normalsBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, normals, gl.STATIC_DRAW); + const vertexBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, monkey.vertices, gl.STATIC_DRAW); + const normalsBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, monkey.normals, gl.STATIC_DRAW); vertexBuffer.bind(gl); gl.vertexAttribPointer(programInfo.attributeLocations.position, 3, gl.FLOAT, false, 0, 0); normalsBuffer.bind(gl); gl.vertexAttribPointer(programInfo.attributeLocations.normal, 3, gl.FLOAT, false, 0, 0); - const modelMatrix = mat4.create(); const viewMatrix = mat4.create(); const projectionMatrix = mat4.create(); - const normalMatrix = mat4.create(); mat4.lookAt( viewMatrix, 100, ); - gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, modelMatrix); gl.uniformMatrix4fv(programInfo.uniformLocations.viewMatrix, false, viewMatrix); gl.uniformMatrix4fv(programInfo.uniformLocations.projectionMatrix, false, projectionMatrix); gl.viewport(0, 0, canvas.width, canvas.height); - gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3); - function frame() { - mat4.rotateY(modelMatrix, modelMatrix, Math.PI / 180); - - mat4.invert(normalMatrix, modelMatrix); - mat4.transpose(normalMatrix, normalMatrix); + mat4.rotateY(monkey.modelMatrix, monkey.modelMatrix, Math.PI / 180); - gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, modelMatrix); - gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, normalMatrix); + gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, monkey.modelMatrix); + gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, monkey.normalMatrix); gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3);

Now let's import more objects

📄 src/3d.js



import { compileShader, setupShaderInput, parseObj } from './gl-helpers'; import { GLBuffer } from './GLBuffer'; import monkeyObj from '../assets/objects/monkey.obj'; + import torusObj from '../assets/objects/torus.obj'; + import coneObj from '../assets/objects/cone.obj'; + import { Object3D } from './Object3D'; const canvas = document.querySelector('canvas'); const programInfo = setupShaderInput(gl, program, vShaderSource, fShaderSource); const monkey = new Object3D(monkeyObj); + const torus = new Object3D(torusObj); + const cone = new Object3D(coneObj); gl.uniform3fv(programInfo.uniformLocations.color, [0.5, 0.5, 0.5]);

and store them in a collection

📄 src/3d.js



const torus = new Object3D(torusObj); const cone = new Object3D(coneObj); + const objects = [ + monkey, + torus, + cone, + ]; + gl.uniform3fv(programInfo.uniformLocations.color, [0.5, 0.5, 0.5]); const vertexBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, monkey.vertices, gl.STATIC_DRAW);

and instead of issuing a draw call for just a monkey, we'll iterate over collection

📄 src/3d.js



gl.viewport(0, 0, canvas.width, canvas.height); function frame() { - mat4.rotateY(monkey.modelMatrix, monkey.modelMatrix, Math.PI / 180); + objects.forEach((object) => { + mat4.rotateY(object.modelMatrix, object.modelMatrix, Math.PI / 180); - gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, monkey.modelMatrix); - gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, monkey.normalMatrix); + gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, object.modelMatrix); + gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, object.normalMatrix); - gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3); + gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3); + }); requestAnimationFrame(frame); }

Ok, but why do we still have only monkey rendered?

No wonder, vertex and normals buffer stays the same, so we just render the same object N times. Let's update vertex and normals buffer each time we want to render an object

📄 src/3d.js



gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, object.modelMatrix); gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, object.normalMatrix); + vertexBuffer.setData(gl, object.vertices, gl.STATIC_DRAW); + normalsBuffer.setData(gl, object.normals, gl.STATIC_DRAW); + gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.data.length / 3); });

Cool, we've rendered multiple objects, but they are all in the same spot. Let's fix that

Each object will have a property storing a position in space

📄 src/3d.js



const programInfo = setupShaderInput(gl, program, vShaderSource, fShaderSource); - const monkey = new Object3D(monkeyObj); - const torus = new Object3D(torusObj); - const cone = new Object3D(coneObj); + const monkey = new Object3D(monkeyObj, [0, 0, 0]); + const torus = new Object3D(torusObj, [-3, 0, 0]); + const cone = new Object3D(coneObj, [3, 0, 0]); const objects = [ monkey,

📄 src/Object3D.js



import { mat4 } from "gl-matrix"; export class Object3D { - constructor(source) { + constructor(source, position) { const { vertices, normals } = parseObj(source); this.vertices = vertices; this.normals = normals; + this.position = position; this.modelMatrix = mat4.create(); this._normalMatrix = mat4.create();

and this position should be respected by model matrix

📄 src/Object3D.js



this.position = position; this.modelMatrix = mat4.create(); + mat4.fromTranslation(this.modelMatrix, position); this._normalMatrix = mat4.create(); }

And one more thing. We can also define a color specific to each object

📄 src/3d.js



const programInfo = setupShaderInput(gl, program, vShaderSource, fShaderSource); - const monkey = new Object3D(monkeyObj, [0, 0, 0]); - const torus = new Object3D(torusObj, [-3, 0, 0]); - const cone = new Object3D(coneObj, [3, 0, 0]); + const monkey = new Object3D(monkeyObj, [0, 0, 0], [1, 0, 0]); + const torus = new Object3D(torusObj, [-3, 0, 0], [0, 1, 0]); + const cone = new Object3D(coneObj, [3, 0, 0], [0, 0, 1]); const objects = [ monkey, cone, ]; - gl.uniform3fv(programInfo.uniformLocations.color, [0.5, 0.5, 0.5]); - const vertexBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, monkey.vertices, gl.STATIC_DRAW); const normalsBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, monkey.normals, gl.STATIC_DRAW); gl.uniformMatrix4fv(programInfo.uniformLocations.modelMatrix, false, object.modelMatrix); gl.uniformMatrix4fv(programInfo.uniformLocations.normalMatrix, false, object.normalMatrix); + gl.uniform3fv(programInfo.uniformLocations.color, object.color); + vertexBuffer.setData(gl, object.vertices, gl.STATIC_DRAW); normalsBuffer.setData(gl, object.normals, gl.STATIC_DRAW);

📄 src/Object3D.js



import { mat4 } from "gl-matrix"; export class Object3D { - constructor(source, position) { + constructor(source, position, color) { const { vertices, normals } = parseObj(source); this.vertices = vertices; this.modelMatrix = mat4.create(); mat4.fromTranslation(this.modelMatrix, position); this._normalMatrix = mat4.create(); + + this.color = color; } get normalMatrix () {

Yay! We now can render multiple objects with individual transforms and colors 🎉

That's it for today, see you tomorrow 👋





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