import { Matrix4 , Shader } from 'three' ; author const MotionBlurShader = { uniforms : { tDiffuse : { value : null } , tDepth : { value : null } , clipToWorldMatrix : { value : new Matrix4 ( ) } , prevWorldToClipMatrix : { value : new Matrix4 ( ) } , intensity : { value : 1.0 } , samples : { value : 32 } , } , vertexShader : `

    varying vec2 vUv;

    void main() {
      vUv = uv;
      gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
    }

  ` , fragmentShader : `

    const int MAX_SAMPLES = 128;

    uniform sampler2D tDiffuse;
    uniform sampler2D tDepth;
    uniform mat4 clipToWorldMatrix;
    uniform mat4 prevWorldToClipMatrix;
    uniform float intensity;
    uniform int samples;
    varying vec2 vUv;

    void main() {
      float zOverW = texture2D(tDepth, vUv).x;
      vec4 clipPosition = vec4(vUv.x, vUv.y, zOverW, 1.0);
      vec4 worldPosition = clipToWorldMatrix * clipPosition;
      worldPosition /= worldPosition.w;

      vec4 prevClipPosition = prevWorldToClipMatrix * worldPosition;
      prevClipPosition /= prevClipPosition.w;
      vec2 velocity = ((clipPosition - prevClipPosition).xy + (clipPosition - prevClipPosition).zz) * intensity;

      vec4 texel = texture2D(tDiffuse, vUv);
      vec2 texelCoord = vUv;
      for (int i = 1; i < MAX_SAMPLES; ++i) {
        if (i >= samples) {
          // hack to allow loop comparisons against uniforms
          break;
        }
        // this offset calculation centers the blur which avoids unevenness favoring the direction of the velocity
        vec2 offset = velocity * (float(i) / float(samples - 1) - 0.5);
        texel += texture2D(tDiffuse, vUv + offset);
      }

      gl_FragColor = texel / max(1.0, float(samples));
    }

  ` , } ; export { MotionBlurShader , } ; export default MotionBlurShader ;