GPUComputationRenderer.js

/**
 * GPUComputationRenderer, based on SimulationRenderer by zz85
 *
 * The GPUComputationRenderer uses the concept of variables. These variables are RGBA float textures that hold 4 floats
 * for each compute element (texel)
 *
 * Each variable has a fragment shader that defines the computation made to obtain the variable in question.
 * You can use as many variables you need, and make dependencies so you can use textures of other variables in the shader
 * (the sampler uniforms are added automatically) Most of the variables will need themselves as dependency.
 *
 * The renderer has actually two render targets per variable, to make ping-pong. Textures from the current frame are used
 * as inputs to render the textures of the next frame.
 *
 * The render targets of the variables can be used as input textures for your visualization shaders.
 *
 * Variable names should be valid identifiers and should not collide with THREE GLSL used identifiers.
 * a common approach could be to use 'texture' prefixing the variable name; i.e texturePosition, textureVelocity...
 *
 * The size of the computation (sizeX * sizeY) is defined as 'resolution' automatically in the shader. For example:
 * #DEFINE resolution vec2( 1024.0, 1024.0 )
 *
 * -------------
 *
 * Basic use:
 *
 * // Initialization...
 *
 * // Create computation renderer
 * const gpuCompute = new GPUComputationRenderer( 1024, 1024, renderer );
 *
 * // Create initial state float textures
 * const pos0 = gpuCompute.createTexture();
 * const vel0 = gpuCompute.createTexture();
 * // and fill in here the texture data...
 *
 * // Add texture variables
 * const velVar = gpuCompute.addVariable( "textureVelocity", fragmentShaderVel, pos0 );
 * const posVar = gpuCompute.addVariable( "texturePosition", fragmentShaderPos, vel0 );
 *
 * // Add variable dependencies
 * gpuCompute.setVariableDependencies( velVar, [ velVar, posVar ] );
 * gpuCompute.setVariableDependencies( posVar, [ velVar, posVar ] );
 *
 * // Add custom uniforms
 * velVar.material.uniforms.time = { value: 0.0 };
 *
 * // Check for completeness
 * const error = gpuCompute.init();
 * if ( error !== null ) {
 *    console.error( error );
  * }
 *
 *
 * // In each frame...
 *
 * // Compute!
 * gpuCompute.compute();
 *
 * // Update texture uniforms in your visualization materials with the gpu renderer output
 * myMaterial.uniforms.myTexture.value = gpuCompute.getCurrentRenderTarget( posVar ).texture;
 *
 * // Do your rendering
 * renderer.render( myScene, myCamera );
 *
 * -------------
 *
 * Also, you can use utility functions to create THREE.ShaderMaterial and perform computations (rendering between textures)
 * Note that the shaders can have multiple input textures.
 *
 * const myFilter1 = gpuCompute.createShaderMaterial( myFilterFragmentShader1, { theTexture: { value: null } } );
 * const myFilter2 = gpuCompute.createShaderMaterial( myFilterFragmentShader2, { theTexture: { value: null } } );
 *
 * const inputTexture = gpuCompute.createTexture();
 *
 * // Fill in here inputTexture...
 *
 * myFilter1.uniforms.theTexture.value = inputTexture;
 *
 * const myRenderTarget = gpuCompute.createRenderTarget();
 * myFilter2.uniforms.theTexture.value = myRenderTarget.texture;
 *
 * const outputRenderTarget = gpuCompute.createRenderTarget();
 *
 * // Now use the output texture where you want:
 * myMaterial.uniforms.map.value = outputRenderTarget.texture;
 *
 * // And compute each frame, before rendering to screen:
 * gpuCompute.doRenderTarget( myFilter1, myRenderTarget );
 * gpuCompute.doRenderTarget( myFilter2, outputRenderTarget );
 *
 *
 *
 * @param {int} sizeX Computation problem size is always 2d: sizeX * sizeY elements.
 * @param {int} sizeY Computation problem size is always 2d: sizeX * sizeY elements.
 * @param {WebGLRenderer} renderer The renderer
  */

class GPUComputationRenderer {

  constructor( sizeX, sizeY, renderer ) {

    this.variables = [];
    this.currentTextureIndex = 0;
    let dataType = THREE.FloatType;
    const scene = new THREE.Scene();
    const camera = new THREE.Camera();
    camera.position.z = 1;
    const passThruUniforms = {
      passThruTexture: {
        value: null
      }
    };
    const passThruShader = createShaderMaterial( getPassThroughFragmentShader(), passThruUniforms );
    const mesh = new THREE.Mesh( new THREE.PlaneGeometry( 2, 2 ), passThruShader );
    scene.add( mesh );

    this.setDataType = function ( type ) {

      dataType = type;
      return this;

    };

    this.addVariable = function ( variableName, computeFragmentShader, initialValueTexture ) {

      const material = this.createShaderMaterial( computeFragmentShader );
      const variable = {
        name: variableName,
        initialValueTexture: initialValueTexture,
        material: material,
        dependencies: null,
        renderTargets: [],
        wrapS: null,
        wrapT: null,
        minFilter: THREE.NearestFilter,
        magFilter: THREE.NearestFilter
      };
      this.variables.push( variable );
      return variable;

    };

    this.setVariableDependencies = function ( variable, dependencies ) {

      variable.dependencies = dependencies;

    };

    this.init = function () {
      if ( renderer.capabilities.isWebGL2 === false && renderer.extensions.has( 'OES_texture_float' ) === false ) {
        return 'No OES_texture_float support for float textures.';

      }

      if ( renderer.capabilities.maxVertexTextures === 0 ) {
        return 'No support for vertex shader textures.';

      }

      for ( let i = 0; i < this.variables.length; i ++ ) {

        const variable = this.variables[ i ]; // Creates rendertargets and initialize them with input texture

        variable.renderTargets[ 0 ] = this.createRenderTarget( sizeX, sizeY, variable.wrapS, variable.wrapT, variable.minFilter, variable.magFilter );
        variable.renderTargets[ 1 ] = this.createRenderTarget( sizeX, sizeY, variable.wrapS, variable.wrapT, variable.minFilter, variable.magFilter );
        this.renderTexture( variable.initialValueTexture, variable.renderTargets[ 0 ] );
        this.renderTexture( variable.initialValueTexture, variable.renderTargets[ 1 ] ); // Adds dependencies uniforms to the THREE.ShaderMaterial

        const material = variable.material;
        const uniforms = material.uniforms;

        if ( variable.dependencies !== null ) {

          for ( let d = 0; d < variable.dependencies.length; d ++ ) {

            const depVar = variable.dependencies[ d ];

            if ( depVar.name !== variable.name ) {

              // Checks if variable exists
              let found = false;

              for ( let j = 0; j < this.variables.length; j ++ ) {

                if ( depVar.name === this.variables[ j ].name ) {

                  found = true;
                  break;

                }

              }

              if ( ! found ) {

                return 'Variable dependency not found. Variable=' + variable.name + ', dependency=' + depVar.name;

              }

            }

            uniforms[ depVar.name ] = {
              value: null
            };
            material.fragmentShader = '\nuniform sampler2D ' + depVar.name + ';\n' + material.fragmentShader;

          }

        }

      }

      this.currentTextureIndex = 0;
      return null;

    };

    this.compute = function () {

      const currentTextureIndex = this.currentTextureIndex;
      const nextTextureIndex = this.currentTextureIndex === 0 ? 1 : 0;

      for ( let i = 0, il = this.variables.length; i < il; i ++ ) {

        const variable = this.variables[ i ]; // Sets texture dependencies uniforms

        if ( variable.dependencies !== null ) {

          const uniforms = variable.material.uniforms;

          for ( let d = 0, dl = variable.dependencies.length; d < dl; d ++ ) {

            const depVar = variable.dependencies[ d ];
            uniforms[ depVar.name ].value = depVar.renderTargets[ currentTextureIndex ].texture;

          }

        } // Performs the computation for this variable


        this.doRenderTarget( variable.material, variable.renderTargets[ nextTextureIndex ] );

      }

      this.currentTextureIndex = nextTextureIndex;

    };

    this.getCurrentRenderTarget = function ( variable ) {

      return variable.renderTargets[ this.currentTextureIndex ];

    };

    this.getAlternateRenderTarget = function ( variable ) {

      return variable.renderTargets[ this.currentTextureIndex === 0 ? 1 : 0 ];

    };

    function addResolutionDefine( materialShader ) {

      materialShader.defines.resolution = 'vec2( ' + sizeX.toFixed( 1 ) + ', ' + sizeY.toFixed( 1 ) + ' )';

    }

    this.addResolutionDefine = addResolutionDefine; // The following functions can be used to compute things manually

    function createShaderMaterial( computeFragmentShader, uniforms ) {

      uniforms = uniforms || {};
      const material = new THREE.ShaderMaterial( {
        uniforms: uniforms,
        vertexShader: getPassThroughVertexShader(),
        fragmentShader: computeFragmentShader
      } );
      addResolutionDefine( material );
      return material;

    }

    this.createShaderMaterial = createShaderMaterial;

    this.createRenderTarget = function ( sizeXTexture, sizeYTexture, wrapS, wrapT, minFilter, magFilter ) {

      sizeXTexture = sizeXTexture || sizeX;
      sizeYTexture = sizeYTexture || sizeY;
      wrapS = wrapS || THREE.ClampToEdgeWrapping;
      wrapT = wrapT || THREE.ClampToEdgeWrapping;
      minFilter = minFilter || THREE.NearestFilter;
      magFilter = magFilter || THREE.NearestFilter;
      const renderTarget = new THREE.WebGLRenderTarget( sizeXTexture, sizeYTexture, {
        wrapS: wrapS,
        wrapT: wrapT,
        minFilter: minFilter,
        magFilter: magFilter,
        format: THREE.RGBAFormat,
        type: dataType,
        depthBuffer: false
      } );
      return renderTarget;

    };

    this.createTexture = function () {

      const data = new Float32Array( sizeX * sizeY * 4 );
      return new THREE.DataTexture( data, sizeX, sizeY, THREE.RGBAFormat, THREE.FloatType );

    };

    this.renderTexture = function ( input, output ) {

      // Takes a texture, and render out in rendertarget
      // input = Texture
      // output = RenderTarget
      passThruUniforms.passThruTexture.value = input;
      this.doRenderTarget( passThruShader, output );
      passThruUniforms.passThruTexture.value = null;

    };

    this.doRenderTarget = function ( material, output ) {

      const currentRenderTarget = renderer.getRenderTarget();
      mesh.material = material;
      renderer.setRenderTarget( output );
      renderer.render( scene, camera );
      mesh.material = passThruShader;
      renderer.setRenderTarget( currentRenderTarget );
    }; // Shaders


    function getPassThroughVertexShader() {

      return 'void main() {\n' + '\n' + ' gl_Position = vec4( position, 1.0 );\n' + '\n' + '}\n';

    }

    function getPassThroughFragmentShader() {

      return 'uniform sampler2D passThruTexture;\n' + '\n' + 'void main() {\n' + '\n' + ' vec2 uv = gl_FragCoord.xy / resolution.xy;\n' + '\n' + '  gl_FragColor = texture2D( passThruTexture, uv );\n' + '\n' + '}\n';
    }
  }
}

export default GPUComputationRenderer;