@arcgis/core/views/3d/webgl-engine/core/shaderLibrary/shading/ScreenSpaceReflections.glsl.js

ArcGIS Maps SDK for JavaScript: A complete 2D and 3D mapping and data visualization API

/* COPYRIGHT Esri - https://js.arcgis.com/5.0.8/LICENSE.txt */
import{ReadDepth as e}from"../output/ReadDepth.glsl.js";import{Float2BindUniform as t}from"../../shaderModules/Float2BindUniform.js";import{FloatBindUniform as o}from"../../shaderModules/FloatBindUniform.js";import{glsl as r}from"../../shaderModules/glsl.js";import{Matrix4BindUniform as i}from"../../shaderModules/Matrix4BindUniform.js";import{Texture2DBindUniform as a}from"../../shaderModules/Texture2DBindUniform.js";function d(d,n){if(!n.screenSpaceReflections)return;const c=d.fragment;c.include(e),c.uniforms.add(new t("nearFar",e=>e.camera.nearFar),new a("depthMap",e=>e.depth?.attachment),new i("proj",e=>e.camera.projectionMatrix),new o("invResolutionHeight",e=>1/e.camera.height),new i("reprojectionMatrix",e=>e.ssr.reprojectionMatrix)).code.add(r`
  vec2 reprojectionCoordinate(vec3 projectionCoordinate)
  {
    vec4 zw = proj * vec4(0.0, 0.0, -projectionCoordinate.z, 1.0);
    vec4 reprojectedCoord = reprojectionMatrix * vec4(zw.w * (projectionCoordinate.xy * 2.0 - 1.0), zw.z, zw.w);
    reprojectedCoord.xy /= reprojectedCoord.w;
    return reprojectedCoord.xy * 0.5 + 0.5;
  }

  const int maxSteps = ${n.highStepCount?"150":"75"};

  vec4 applyProjectionMat(mat4 projectionMat, vec3 x)
  {
    vec4 projectedCoord =  projectionMat * vec4(x, 1.0);
    projectedCoord.xy /= projectedCoord.w;
    projectedCoord.xy = projectedCoord.xy*0.5 + 0.5;
    return projectedCoord;
  }

  vec3 screenSpaceIntersection(vec3 dir, vec3 startPosition, vec3 viewDir, vec3 normal)
  {
    vec3 viewPos = startPosition;
    vec3 viewPosEnd = startPosition;

    // Project the start position to the screen
    vec4 projectedCoordStart = applyProjectionMat(proj, viewPos);
    vec3  Q0 = viewPos / projectedCoordStart.w; // homogeneous camera space
    float k0 = 1.0/ projectedCoordStart.w;

    // advance the position in the direction of the reflection
    viewPos += dir;

    vec4 projectedCoordVanishingPoint = applyProjectionMat(proj, dir);

    // Project the advanced position to the screen
    vec4 projectedCoordEnd = applyProjectionMat(proj, viewPos);
    vec3  Q1 = viewPos / projectedCoordEnd.w; // homogeneous camera space
    float k1 = 1.0/ projectedCoordEnd.w;

    // calculate the reflection direction in the screen space
    vec2 projectedCoordDir = (projectedCoordEnd.xy - projectedCoordStart.xy);
    vec2 projectedCoordDistVanishingPoint = (projectedCoordVanishingPoint.xy - projectedCoordStart.xy);

    float yMod = min(abs(projectedCoordDistVanishingPoint.y), 1.0);

    float projectedCoordDirLength = length(projectedCoordDir);
    float maxSt = float(maxSteps);

    // normalize the projection direction depending on maximum steps
    // this determines how blocky the reflection looks
    vec2 dP = yMod * (projectedCoordDir)/(maxSt * projectedCoordDirLength);

    // Normalize the homogeneous camera space coordinates
    vec3  dQ = yMod * (Q1 - Q0)/(maxSt * projectedCoordDirLength);
    float dk = yMod * (k1 - k0)/(maxSt * projectedCoordDirLength);

    // initialize the variables for ray marching
    vec2 P = projectedCoordStart.xy;
    vec3 Q = Q0;
    float k = k0;
    float rayStartZ = -startPosition.z; // estimated ray start depth value
    float rayEndZ = -startPosition.z;   // estimated ray end depth value
    float prevEstimateZ = -startPosition.z;
    float rayDiffZ = 0.0;
    float dDepth;
    float depth;
    float rayDiffZOld = 0.0;

    // early outs
    if (dot(normal, dir) < 0.0 || dot(-viewDir, normal) < 0.0)
      return vec3(P, 0.0);
    float dDepthBefore = 0.0;

    for(int i = 0; i < maxSteps-1; i++)
    {
      depth = -linearDepthFromTexture(depthMap, P); // get linear depth from the depth buffer

      // estimate depth of the marching ray
      rayStartZ = prevEstimateZ;
      dDepth = -rayStartZ - depth;
      rayEndZ = (dQ.z * 0.5 + Q.z)/ ((dk * 0.5 + k));
      rayDiffZ = rayEndZ- rayStartZ;
      prevEstimateZ = rayEndZ;

      if(-rayEndZ > nearFar[1] || -rayEndZ < nearFar[0] || P.y < 0.0  || P.y > 1.0 )
      {
        return vec3(P, 0.);
      }

      // If we detect a hit - return the intersection point, two conditions:
      //  - dDepth > 0.0 - sampled point depth is in front of estimated depth
      //  - if difference between dDepth and rayDiffZOld is not too large
      //  - if difference between dDepth and 0.025/abs(k) is not too large
      //  - if the sampled depth is not behind far plane or in front of near plane

      if((dDepth) < 0.025/abs(k) + abs(rayDiffZ) && dDepth > 0.0 && depth > nearFar[0] && depth < nearFar[1] && abs(P.y - projectedCoordStart.y) > invResolutionHeight)
      {
        float weight = dDepth / (dDepth - dDepthBefore);
        vec2 Pf = mix(P - dP, P, 1.0 - weight);
        if (abs(Pf.y - projectedCoordStart.y) > invResolutionHeight) {
          return vec3(Pf, depth);
        }
        else {
          return vec3(P, depth);
        }
      }

      // continue with ray marching
      P = clamp(P + dP, vec2(0.0), vec2(0.999));
      Q.z += dQ.z;
      k += dk;
      rayDiffZOld = rayDiffZ;
      dDepthBefore = dDepth;
    }
    return vec3(P, 0.0);
  }
  `)}export{d as ScreenSpaceReflections};