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WebGL Month. Day 11. Reducing WebGL boilerplate

lesnitsky profile image Andrei Lesnitsky Updated on ・6 min read

Reducing boilerplate

This is a series of blog posts related to WebGL. New post will be available every day

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Yesterday we've learned how to use multiple textures. This required a shader modification, as well as javascript, but this changes might be partially done automatically

There is a package glsl-extract-sync which can get the info about shader attributes and uniforms

Install this package with

npm i glsl-extract-sync

📄 package.json

      "url-loader": "^2.0.1",
      "webpack": "^4.35.2",
      "webpack-cli": "^3.3.5"
+   },
+   "dependencies": {
+     "glsl-extract-sync": "0.0.0"
    }
  }

Now let's create a helper function which will get all references to attributes and uniforms with help of this package

📄 src/gl-helpers.js

+ import extract from 'glsl-extract-sync';
+ 
  export function compileShader(gl, shader, source) {
      gl.shaderSource(shader, source);
      gl.compileShader(shader);
          img,
      );
  }
+ 
+ export function setupShaderInput(gl, program, vShaderSource, fShaderSource) {
+ 
+ }

We need to extract info about both vertex and fragment shaders

📄 src/gl-helpers.js

  }

  export function setupShaderInput(gl, program, vShaderSource, fShaderSource) {
- 
+     const vShaderInfo = extract(vShaderSource);
+     const fShaderInfo = extract(fShaderSource);
  }

📄 src/texture.js

  import vShaderSource from './shaders/texture.v.glsl';
  import fShaderSource from './shaders/texture.f.glsl';
- import { compileShader, loadImage, createTexture, setImage } from './gl-helpers';
+ import { compileShader, loadImage, createTexture, setImage, setupShaderInput } from './gl-helpers';
  import { createRect } from './shape-helpers';

  import textureImageSrc from '../assets/images/texture.jpg';
  gl.bindBuffer(gl.ARRAY_BUFFER, vertexPositionBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, vertexPosition, gl.STATIC_DRAW);

+ console.log(setupShaderInput(gl, program, vShaderSource, fShaderSource));
+ 
  const attributeLocations = {
      position: gl.getAttribLocation(program, 'position'),
      texCoord: gl.getAttribLocation(program, 'texCoord'),

Only vertex shader might have attributes, but uniforms may be defined in both shaders

📄 src/gl-helpers.js

  export function setupShaderInput(gl, program, vShaderSource, fShaderSource) {
      const vShaderInfo = extract(vShaderSource);
      const fShaderInfo = extract(fShaderSource);
+ 
+     const attributes = vShaderInfo.attributes;
+     const uniforms = [
+         ...vShaderInfo.uniforms,
+         ...fShaderInfo.uniforms,
+     ];
  }

Now we can get all attribute locations

📄 src/gl-helpers.js

          ...vShaderInfo.uniforms,
          ...fShaderInfo.uniforms,
      ];
+ 
+     const attributeLocations = attributes.reduce((attrsMap, attr) => {
+         attrsMap[attr.name] = gl.getAttribLocation(program, attr.name);
+         return attrsMap;
+     }, {});
  }

and enable all attributes

📄 src/gl-helpers.js

          attrsMap[attr.name] = gl.getAttribLocation(program, attr.name);
          return attrsMap;
      }, {});
+ 
+     attributes.forEach((attr) => {
+         gl.enableVertexAttribArray(attributeLocations[attr.name]);
+     });
  }

We should also get all uniform locations

📄 src/gl-helpers.js

      attributes.forEach((attr) => {
          gl.enableVertexAttribArray(attributeLocations[attr.name]);
      });
+ 
+     const uniformLocations = uniforms.reduce((uniformsMap, uniform) => {
+         uniformsMap[uniform.name] = gl.getUniformLocation(program, uniform.name);
+         return uniformsMap;
+     }, {});
  }

and finally return attribute and uniform locations

📄 src/gl-helpers.js

          uniformsMap[uniform.name] = gl.getUniformLocation(program, uniform.name);
          return uniformsMap;
      }, {});
+ 
+     return {
+         attributeLocations,
+         uniformLocations,
+     }
  }

Ok, let's get advantage of our new sweet helper

📄 src/texture.js

  gl.bindBuffer(gl.ARRAY_BUFFER, vertexPositionBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, vertexPosition, gl.STATIC_DRAW);

- console.log(setupShaderInput(gl, program, vShaderSource, fShaderSource));
+ const programInfo = setupShaderInput(gl, program, vShaderSource, fShaderSource);

- const attributeLocations = {
-     position: gl.getAttribLocation(program, 'position'),
-     texCoord: gl.getAttribLocation(program, 'texCoord'),
-     texIndex: gl.getAttribLocation(program, 'texIndex'),
- };
- 
- const uniformLocations = {
-     texture: gl.getUniformLocation(program, 'texture'),
-     otherTexture: gl.getUniformLocation(program, 'otherTexture'),
-     resolution: gl.getUniformLocation(program, 'resolution'),
- };
- 
- gl.enableVertexAttribArray(attributeLocations.position);
- gl.vertexAttribPointer(attributeLocations.position, 2, gl.FLOAT, false, 0, 0);
+ gl.vertexAttribPointer(programInfo.attributeLocations.position, 2, gl.FLOAT, false, 0, 0);

  gl.bindBuffer(gl.ARRAY_BUFFER, texCoordsBuffer);
- 
- gl.enableVertexAttribArray(attributeLocations.texCoord);
- gl.vertexAttribPointer(attributeLocations.texCoord, 2, gl.FLOAT, false, 0, 0);
+ gl.vertexAttribPointer(programInfo.attributeLocations.texCoord, 2, gl.FLOAT, false, 0, 0);

  gl.bindBuffer(gl.ARRAY_BUFFER, texIndiciesBuffer);
- 
- gl.enableVertexAttribArray(attributeLocations.texIndex);
- gl.vertexAttribPointer(attributeLocations.texIndex, 1, gl.FLOAT, false, 0, 0);
+ gl.vertexAttribPointer(programInfo.attributeLocations.texIndex, 1, gl.FLOAT, false, 0, 0);

  const vertexIndices = new Uint8Array([
      // left rect

      gl.activeTexture(gl.TEXTURE0);
      gl.bindTexture(gl.TEXTURE_2D, texture);
-     gl.uniform1i(uniformLocations.texture, 0);
+     gl.uniform1i(programInfo.uniformLocations.texture, 0);

      gl.activeTexture(gl.TEXTURE1);
      gl.bindTexture(gl.TEXTURE_2D, otherTexture);
-     gl.uniform1i(uniformLocations.otherTexture, 1);
+     gl.uniform1i(programInfo.uniformLocations.otherTexture, 1);

-     gl.uniform2fv(uniformLocations.resolution, [canvas.width, canvas.height]);
+     gl.uniform2fv(programInfo.uniformLocations.resolution, [canvas.width, canvas.height]);

      gl.drawElements(gl.TRIANGLES, vertexIndices.length, gl.UNSIGNED_BYTE, 0);
  });

Looks quite like a cleanup 😎

One more thing that we use often are buffers.
Let's create a helper class

📄 src/GLBuffer.js

export class GLBuffer {
    constructor(gl, target, data) {

    }
}

We'll need data, buffer target and actual gl buffer, so let's assign everything passed from outside and craete a gl buffer.

📄 src/GLBuffer.js

  export class GLBuffer {
      constructor(gl, target, data) {
- 
+         this.target = target;
+         this.data = data;
+         this.glBuffer = gl.createBuffer();
      }
  }

We didn't assign a gl to instance because it might cause a memory leak, so we'll need to pass it from outside

Let's implement an alternative to a gl.bindBuffer

📄 src/GLBuffer.js

          this.data = data;
          this.glBuffer = gl.createBuffer();
      }
+ 
+     bind(gl) {
+         gl.bindBuffer(this.target, this.glBuffer);
+     }
  }

and a convenient way to set buffer data

📄 src/GLBuffer.js

      bind(gl) {
          gl.bindBuffer(this.target, this.glBuffer);
      }
+ 
+     setData(gl, data, usage) {
+         this.data = data;
+         this.bind(gl);
+         gl.bufferData(this.target, this.data, usage);
+     }
  }

Now let's make a data argument of constructor and add a usage argument to be able to do everything we need with just a constructor call

📄 src/GLBuffer.js

  export class GLBuffer {
-     constructor(gl, target, data) {
+     constructor(gl, target, data, usage) {
          this.target = target;
          this.data = data;
          this.glBuffer = gl.createBuffer();
+ 
+         if (typeof data !== 'undefined') {
+             this.setData(gl, data, usage);
+         }
      }

      bind(gl) {

Cool, now we can replace texCoords buffer with our thin wrapper

📄 src/texture.js


  import textureImageSrc from '../assets/images/texture.jpg';
  import textureGreenImageSrc from '../assets/images/texture-green.jpg';
+ import { GLBuffer } from './GLBuffer';

  const canvas = document.querySelector('canvas');
  const gl = canvas.getContext('webgl');
  gl.linkProgram(program);
  gl.useProgram(program);

- const texCoords = new Float32Array([
+ const texCoordsBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, new Float32Array([
      ...createRect(0, 0, 1, 1), // left rect
      ...createRect(0, 0, 1, 1), // right rect
- ]);
- const texCoordsBuffer = gl.createBuffer();
- 
- gl.bindBuffer(gl.ARRAY_BUFFER, texCoordsBuffer);
- gl.bufferData(gl.ARRAY_BUFFER, texCoords, gl.STATIC_DRAW);
+ ]), gl.STATIC_DRAW);

  const texIndicies = new Float32Array([
      ...Array.from({ length: 4 }).fill(0), // left rect

  gl.vertexAttribPointer(programInfo.attributeLocations.position, 2, gl.FLOAT, false, 0, 0);

- gl.bindBuffer(gl.ARRAY_BUFFER, texCoordsBuffer);
+ texCoordsBuffer.bind(gl);
  gl.vertexAttribPointer(programInfo.attributeLocations.texCoord, 2, gl.FLOAT, false, 0, 0);

  gl.bindBuffer(gl.ARRAY_BUFFER, texIndiciesBuffer);

Do the same for texIndices buffer

📄 src/texture.js

      ...createRect(0, 0, 1, 1), // right rect
  ]), gl.STATIC_DRAW);

- const texIndicies = new Float32Array([
+ const texIndiciesBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, new Float32Array([
      ...Array.from({ length: 4 }).fill(0), // left rect
      ...Array.from({ length: 4 }).fill(1), // right rect
- ]);
- const texIndiciesBuffer = gl.createBuffer();
- 
- gl.bindBuffer(gl.ARRAY_BUFFER, texIndiciesBuffer);
- gl.bufferData(gl.ARRAY_BUFFER, texIndicies, gl.STATIC_DRAW);
+ ]), gl.STATIC_DRAW);

  const vertexPosition = new Float32Array([
      ...createRect(-1, -1, 1, 2), // left rect
  texCoordsBuffer.bind(gl);
  gl.vertexAttribPointer(programInfo.attributeLocations.texCoord, 2, gl.FLOAT, false, 0, 0);

- gl.bindBuffer(gl.ARRAY_BUFFER, texIndiciesBuffer);
+ texIndiciesBuffer.bind(gl);
  gl.vertexAttribPointer(programInfo.attributeLocations.texIndex, 1, gl.FLOAT, false, 0, 0);

  const vertexIndices = new Uint8Array([

vertex positions

📄 src/texture.js

      ...Array.from({ length: 4 }).fill(1), // right rect
  ]), gl.STATIC_DRAW);

- const vertexPosition = new Float32Array([
+ const vertexPositionBuffer = new GLBuffer(gl, gl.ARRAY_BUFFER, new Float32Array([
      ...createRect(-1, -1, 1, 2), // left rect
      ...createRect(-1, 0, 1, 2), // right rect
- ]);
- const vertexPositionBuffer = gl.createBuffer();
+ ]), gl.STATIC_DRAW);

- gl.bindBuffer(gl.ARRAY_BUFFER, vertexPositionBuffer);
- gl.bufferData(gl.ARRAY_BUFFER, vertexPosition, gl.STATIC_DRAW);

  const programInfo = setupShaderInput(gl, program, vShaderSource, fShaderSource);

+ vertexPositionBuffer.bind(gl);
  gl.vertexAttribPointer(programInfo.attributeLocations.position, 2, gl.FLOAT, false, 0, 0);

  texCoordsBuffer.bind(gl);

and index buffer

📄 src/texture.js

  texIndiciesBuffer.bind(gl);
  gl.vertexAttribPointer(programInfo.attributeLocations.texIndex, 1, gl.FLOAT, false, 0, 0);

- const vertexIndices = new Uint8Array([
+ const indexBuffer = new GLBuffer(gl, gl.ELEMENT_ARRAY_BUFFER, new Uint8Array([
      // left rect
      0, 1, 2, 
      1, 2, 3, 
      // right rect
      4, 5, 6, 
      5, 6, 7,
- ]);
- const indexBuffer = gl.createBuffer();
- 
- gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
- gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, vertexIndices, gl.STATIC_DRAW);
+ ]), gl.STATIC_DRAW);

  Promise.all([
      loadImage(textureImageSrc),

      gl.uniform2fv(programInfo.uniformLocations.resolution, [canvas.width, canvas.height]);

-     gl.drawElements(gl.TRIANGLES, vertexIndices.length, gl.UNSIGNED_BYTE, 0);
+     gl.drawElements(gl.TRIANGLES, indexBuffer.data.length, gl.UNSIGNED_BYTE, 0);
  });

Now we are able to work with shaders being more productive with less code!

See you tomorrow 👋


This is a series of blog posts related to WebGL. New post will be available every day

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Join mailing list to get new posts right to your inbox

Source code available here

Built with

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