text: import {
    Camera,
    ClampToEdgeWrapping,
    DataTexture,
    FloatType,
    Mesh,
    NearestFilter,
    PlaneGeometry,
    RGBAFormat,
    Scene,
    ShaderMaterial,
    WebGLRenderTarget,
  } from 'three'
  
  /**
   * 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
   * var gpuCompute = new GPUComputationRenderer( 1024, 1024, renderer );
   *
   * // Create initial state float textures
   * var pos0 = gpuCompute.createTexture();
   * var vel0 = gpuCompute.createTexture();
   * // and fill in here the texture data...
   *
   * // Add texture variables
   * var velVar = gpuCompute.addVariable( "textureVelocity", fragmentShaderVel, pos0 );
   * var 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
   * var 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 ShaderMaterial and perform computations (rendering between textures)
   * Note that the shaders can have multiple input textures.
   *
   * var myFilter1 = gpuCompute.createShaderMaterial( myFilterFragmentShader1, { theTexture: { value: null } } );
   * var myFilter2 = gpuCompute.createShaderMaterial( myFilterFragmentShader2, { theTexture: { value: null } } );
   *
   * var inputTexture = gpuCompute.createTexture();
   *
   * // Fill in here inputTexture...
   *
   * myFilter1.uniforms.theTexture.value = inputTexture;
   *
   * var myRenderTarget = gpuCompute.createRenderTarget();
   * myFilter2.uniforms.theTexture.value = myRenderTarget.texture;
   *
   * var 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
   */
  
  var GPUComputationRenderer = function (sizeX, sizeY, renderer) {
    this.variables = []
  
    this.currentTextureIndex = 0
  
    var dataType = FloatType
  
    var scene = new Scene()
  
    var camera = new Camera()
    camera.position.z = 1
  
    var passThruUniforms = {
      passThruTexture: { value: null },
    }
  
    var passThruShader = createShaderMaterial(getPassThroughFragmentShader(), passThruUniforms)
  
    var mesh = new Mesh(new PlaneGeometry(2, 2), passThruShader)
    scene.add(mesh)
  
    this.setDataType = function (type) {
      dataType = type
      return this
    }
  
    this.addVariable = function (variableName, computeFragmentShader, initialValueTexture) {
      var material = this.createShaderMaterial(computeFragmentShader)
  
      var variable = {
        name: variableName,
        initialValueTexture: initialValueTexture,
        material: material,
        dependencies: null,
        renderTargets: [],
        wrapS: null,
        wrapT: null,
        minFilter: NearestFilter,
        magFilter: 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 (var i = 0; i < this.variables.length; i++) {
        var 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 ShaderMaterial
        var material = variable.material
        var uniforms = material.uniforms
  
        if (variable.dependencies !== null) {
          for (var d = 0; d < variable.dependencies.length; d++) {
            var depVar = variable.dependencies[d]
  
            if (depVar.name !== variable.name) {
              // Checks if variable exists
              var found = false
              for (var 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 () {
      var currentTextureIndex = this.currentTextureIndex
      var nextTextureIndex = this.currentTextureIndex === 0 ? 1 : 0
  
      for (var i = 0, il = this.variables.length; i < il; i++) {
        var variable = this.variables[i]
  
        // Sets texture dependencies uniforms
        if (variable.dependencies !== null) {
          var uniforms = variable.material.uniforms
          for (var d = 0, dl = variable.dependencies.length; d < dl; d++) {
            var 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 || {}
  
      var material = new 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 || ClampToEdgeWrapping
      wrapT = wrapT || ClampToEdgeWrapping
  
      minFilter = minFilter || NearestFilter
      magFilter = magFilter || NearestFilter
  
      var renderTarget = new WebGLRenderTarget(sizeXTexture, sizeYTexture, {
        wrapS: wrapS,
        wrapT: wrapT,
        minFilter: minFilter,
        magFilter: magFilter,
        format: RGBAFormat,
        type: dataType,
        depthBuffer: false,
      })
  
      return renderTarget
    }
  
    this.createTexture = function () {
      var data = new Float32Array(sizeX * sizeY * 4)
      return new DataTexture(data, sizeX, sizeY, RGBAFormat, 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) {
      var 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 { GPUComputationRenderer }
  