CesiumGS · ggetz · Mar 22, 2024 · Feb 21, 2024 · Feb 22, 2024 · Feb 22, 2024
diff --git a/CHANGES.md b/CHANGES.md
@@ -17,6 +17,7 @@
 ##### Additions :tada:
 
 - Surface normals are now computed for clipping and shape bounds in VoxelEllipsoidShape and VoxelCylinderShape. [#11847](https://github.com/CesiumGS/cesium/pull/11847)
+- Implemented sharper rendering and lighting on voxels with CYLINDER and ELLIPSOID shape. [#11076](https://github.com/CesiumGS/cesium/pull/11076)
 
 ### 1.115 - 2024-03-01
 

diff --git a/packages/engine/Source/Scene/VoxelBoxShape.js b/packages/engine/Source/Scene/VoxelBoxShape.js
@@ -427,21 +427,6 @@ VoxelBoxShape.prototype.computeOrientedBoundingBoxForSample = function (
   );
 };
 
-/**
- * Computes an approximate step size for raymarching the root tile of a voxel grid.
- * The update function must be called before calling this function.
- *
- * @param {Cartesian3} dimensions The voxel grid dimensions for a tile.
- * @returns {number} The step size.
- */
-VoxelBoxShape.prototype.computeApproximateStepSize = function (dimensions) {
-  //>>includeStart('debug', pragmas.debug);
-  Check.typeOf.object("dimensions", dimensions);
-  //>>includeEnd('debug');
-
-  return 1.0 / Cartesian3.maximumComponent(dimensions);
-};
-
 /**
  * Defines the minimum bounds of the shape. Corresponds to minimum X, Y, Z.
  *

diff --git a/packages/engine/Source/Scene/VoxelCylinderShape.js b/packages/engine/Source/Scene/VoxelCylinderShape.js
@@ -660,67 +660,6 @@ VoxelCylinderShape.prototype.computeOrientedBoundingBoxForSample = function (
   );
 };
 
-const scratchOrientedBoundingBox = new OrientedBoundingBox();
-const scratchVoxelScale = new Cartesian3();
-const scratchRootScale = new Cartesian3();
-const scratchScaleRatio = new Cartesian3();
-
-/**
- * Computes an approximate step size for raymarching the root tile of a voxel grid.
- * The update function must be called before calling this function.
- *
- * @param {Cartesian3} dimensions The voxel grid dimensions for a tile.
- * @returns {number} The step size.
- */
-VoxelCylinderShape.prototype.computeApproximateStepSize = function (
-  dimensions
-) {
-  //>>includeStart('debug', pragmas.debug);
-  Check.typeOf.object("dimensions", dimensions);
-  //>>includeEnd('debug');
-
-  const shapeTransform = this.shapeTransform;
-  const minRadius = this._minimumRadius;
-  const maxRadius = this._maximumRadius;
-  const minHeight = this._minimumHeight;
-  const maxHeight = this._maximumHeight;
-  const minAngle = this._minimumAngle;
-  const maxAngle = this._maximumAngle;
-
-  const lerpRadius = 1.0 - 1.0 / dimensions.x;
-  const lerpHeight = 1.0 - 1.0 / dimensions.y;
-  const lerpAngle = 1.0 - 1.0 / dimensions.z;
-
-  // Compare the size of an outermost cylinder voxel to the total cylinder
-  const voxelMinimumRadius = CesiumMath.lerp(minRadius, maxRadius, lerpRadius);
-  const voxelMinimumHeight = CesiumMath.lerp(minHeight, maxHeight, lerpHeight);
-  const voxelMinimumAngle = CesiumMath.lerp(minAngle, maxAngle, lerpAngle);
-  const voxelMaximumRadius = maxRadius;
-  const voxelMaximumHeight = maxHeight;
-  const voxelMaximumAngle = maxAngle;
-
-  const voxelObb = getCylinderChunkObb(
-    voxelMinimumRadius,
-    voxelMaximumRadius,
-    voxelMinimumHeight,
-    voxelMaximumHeight,
-    voxelMinimumAngle,
-    voxelMaximumAngle,
-    shapeTransform,
-    scratchOrientedBoundingBox
-  );
-
-  const voxelScale = Matrix3.getScale(voxelObb.halfAxes, scratchVoxelScale);
-  const rootScale = Matrix4.getScale(shapeTransform, scratchRootScale);
-  const scaleRatio = Cartesian3.divideComponents(
-    voxelScale,
-    rootScale,
-    scratchScaleRatio
-  );
-  const stepSize = Cartesian3.minimumComponent(scaleRatio);
-  return stepSize;
-};
-
 /**
  * Defines the minimum bounds of the shape. Corresponds to minimum radius, height, angle.
  *

diff --git a/packages/engine/Source/Scene/VoxelEllipsoidShape.js b/packages/engine/Source/Scene/VoxelEllipsoidShape.js
@@ -96,6 +96,7 @@ function VoxelEllipsoidShape() {
   this.shaderUniforms = {
     ellipsoidRadiiUv: new Cartesian3(),
     eccentricitySquared: 0.0,
+    evoluteScale: new Cartesian2(),
     ellipsoidInverseRadiiSquaredUv: new Cartesian3(),
     ellipsoidRenderLongitudeMinMax: new Cartesian2(),
     ellipsoidShapeUvLongitudeMinMaxMid: new Cartesian3(),
@@ -420,9 +421,14 @@ VoxelEllipsoidShape.prototype.update = function (
     shapeMaxExtent,
     shaderUniforms.ellipsoidRadiiUv
   );
-  const axisRatio =
-    Cartesian3.minimumComponent(shapeOuterExtent) / shapeMaxExtent;
+  const { x: radiiUvX, z: radiiUvZ } = shaderUniforms.ellipsoidRadiiUv;
+  const axisRatio = radiiUvZ / radiiUvX;
   shaderUniforms.eccentricitySquared = 1.0 - axisRatio * axisRatio;
+  shaderUniforms.evoluteScale = Cartesian2.fromElements(
+    (radiiUvX * radiiUvX - radiiUvZ * radiiUvZ) / radiiUvX,
+    (radiiUvZ * radiiUvZ - radiiUvX * radiiUvX) / radiiUvZ,
+    shaderUniforms.evoluteScale
+  );
 
   // Used to compute geodetic surface normal.
   shaderUniforms.ellipsoidInverseRadiiSquaredUv = Cartesian3.divideComponents(
@@ -816,31 +822,6 @@ VoxelEllipsoidShape.prototype.computeOrientedBoundingBoxForSample = function (
   );
 };
 
-/**
- * Computes an approximate step size for raymarching the root tile of a voxel grid.
- * The update function must be called before calling this function.
- *
- * @param {Cartesian3} dimensions The voxel grid dimensions for a tile.
- * @returns {number} The step size.
- */
-VoxelEllipsoidShape.prototype.computeApproximateStepSize = function (
-  dimensions
-) {
-  //>>includeStart('debug', pragmas.debug);
-  Check.typeOf.object("dimensions", dimensions);
-  //>>includeEnd('debug');
-
-  const ellipsoid = this._ellipsoid;
-  const ellipsoidMaximumRadius = ellipsoid.maximumRadius;
-  const minimumHeight = this._minimumHeight;
-  const maximumHeight = this._maximumHeight;
-
-  const shellToEllipsoidRatio =
-    (maximumHeight - minimumHeight) / (ellipsoidMaximumRadius + maximumHeight);
-  const stepSize = (0.5 * shellToEllipsoidRatio) / dimensions.z;
-  return stepSize;
-};
-
 /**
  * Computes an {@link OrientedBoundingBox} for a subregion of the shape.
  *

diff --git a/packages/engine/Source/Scene/VoxelPrimitive.js b/packages/engine/Source/Scene/VoxelPrimitive.js
@@ -320,12 +320,6 @@ function VoxelPrimitive(options) {
    */
   this._transformNormalLocalToWorld = new Matrix3();
 
-  /**
-   * @type {number}
-   * @private
-   */
-  this._stepSizeUv = 1.0;
-
   // Rendering
   /**
    * @type {boolean}
@@ -1132,7 +1126,7 @@ VoxelPrimitive.prototype.update = function (frameState) {
     cameraPositionWorld,
     uniforms.cameraPositionUv
   );
-  uniforms.stepSize = this._stepSizeUv * this._stepSizeMultiplier;
+  uniforms.stepSize = this._stepSizeMultiplier;
 
   // Render the primitive
   const command = frameState.passes.pick
@@ -1345,8 +1339,6 @@ function updateShapeAndTransforms(primitive, shape, provider) {
   );
 
   // Set member variables when the shape is dirty
-  const dimensions = provider.dimensions;
-  primitive._stepSizeUv = shape.computeApproximateStepSize(dimensions);
   primitive._transformPositionWorldToUv = Matrix4.multiplyTransformation(
     transformPositionLocalToUv,
     transformPositionWorldToLocal,

diff --git a/packages/engine/Source/Scene/VoxelRenderResources.js b/packages/engine/Source/Scene/VoxelRenderResources.js
@@ -3,6 +3,7 @@ import combine from "../Core/combine.js";
 import defined from "../Core/defined.js";
 import ShaderBuilder from "../Renderer/ShaderBuilder.js";
 import ShaderDestination from "../Renderer/ShaderDestination.js";
+import VoxelUtils from "../Shaders/Voxels/VoxelUtils.js";
 import VoxelFS from "../Shaders/Voxels/VoxelFS.js";
 import VoxelVS from "../Shaders/Voxels/VoxelVS.js";
 import IntersectionUtils from "../Shaders/Voxels/IntersectionUtils.js";
@@ -89,6 +90,7 @@ function VoxelRenderResources(primitive) {
     customShader.fragmentShaderText,
     "#line 0",
     Octree,
+    VoxelUtils,
     IntersectionUtils,
     Megatexture,
   ]);
@@ -124,7 +126,6 @@ function VoxelRenderResources(primitive) {
 
   const shapeType = primitive._provider.shape;
   if (shapeType === "BOX") {
-    shaderBuilder.addDefine("SHAPE_BOX", undefined, ShaderDestination.FRAGMENT);
     shaderBuilder.addFragmentLines([
       convertUvToBox,
       IntersectBox,
@@ -138,6 +139,11 @@ function VoxelRenderResources(primitive) {
       Intersection,
     ]);
   } else if (shapeType === "ELLIPSOID") {
+    shaderBuilder.addDefine(
+      "SHAPE_ELLIPSOID",
+      undefined,
+      ShaderDestination.FRAGMENT
+    );
     shaderBuilder.addFragmentLines([
       convertUvToEllipsoid,
       IntersectLongitude,

diff --git a/packages/engine/Source/Scene/VoxelShape.js b/packages/engine/Source/Scene/VoxelShape.js
@@ -130,16 +130,6 @@ VoxelShape.prototype.computeOrientedBoundingBoxForTile =
 VoxelShape.prototype.computeOrientedBoundingBoxForSample =
   DeveloperError.throwInstantiationError;
 
-/**
- * Computes an approximate step size for raymarching the root tile of a voxel grid.
- * The update function must be called before calling this function.
- *
- * @param {Cartesian3} voxelDimensions The voxel grid dimensions for a tile.
- * @returns {number} The step size.
- */
-VoxelShape.prototype.computeApproximateStepSize =
-  DeveloperError.throwInstantiationError;
-
 /**
  * Defines the minimum bounds of the shape. The meaning can vary per-shape.
  *

diff --git a/packages/engine/Source/Scene/processVoxelProperties.js b/packages/engine/Source/Scene/processVoxelProperties.js
@@ -153,6 +153,7 @@ function processVoxelProperties(renderResources, primitive) {
   shaderBuilder.addStructField(voxelStructId, "vec3", "viewDirWorld");
   shaderBuilder.addStructField(voxelStructId, "vec3", "surfaceNormal");
   shaderBuilder.addStructField(voxelStructId, "float", "travelDistance");
+  shaderBuilder.addStructField(voxelStructId, "int", "stepCount");
   shaderBuilder.addStructField(voxelStructId, "int", "tileIndex");
   shaderBuilder.addStructField(voxelStructId, "int", "sampleIndex");
 

diff --git a/packages/engine/Source/Shaders/Voxels/IntersectBox.glsl b/packages/engine/Source/Shaders/Voxels/IntersectBox.glsl
@@ -1,5 +1,5 @@
-// See IntersectionUtils.glsl for the definitions of Ray and NO_HIT
-// See convertUvToBox.glsl for the definition of convertShapeUvToUvSpace
+// See IntersectionUtils.glsl for the definitions of Ray, RayShapeIntersection,
+// NO_HIT, Intersections
 
 /* Box defines (set in Scene/VoxelBoxShape.js)
 #define BOX_INTERSECTION_INDEX ### // always 0
@@ -8,66 +8,40 @@
 uniform vec3 u_renderMinBounds;
 uniform vec3 u_renderMaxBounds;
 
-struct Box {
-    vec3 p0;
-    vec3 p1;
-};
-
-Box constructVoxelBox(in ivec4 octreeCoords, in vec3 tileUv)
-{
-    // Find the min/max cornerpoints of the voxel in tile coordinates
-    vec3 tileOrigin = vec3(octreeCoords.xyz);
-    vec3 numSamples = vec3(u_dimensions);
-    vec3 voxelSize = 1.0 / numSamples;
-    vec3 coordP0 = floor(tileUv * numSamples) * voxelSize + tileOrigin;
-    vec3 coordP1 = coordP0 + voxelSize;
-
-    // Transform to the UV coordinates of the scaled tileset
-    float tileSize = 1.0 / pow(2.0, float(octreeCoords.w));
-    vec3 p0 = convertShapeUvToUvSpace(coordP0 * tileSize);
-    vec3 p1 = convertShapeUvToUvSpace(coordP1 * tileSize);
-
-    return Box(p0, p1);
-}
-
-vec3 getBoxNormal(in Box box, in Ray ray, in float t)
-{
-    vec3 hitPoint = ray.pos + t * ray.dir;
-    vec3 lower = step(hitPoint, box.p0);
-    vec3 upper = step(box.p1, hitPoint);
-    return normalize(upper - lower);
-}
-
-// Find the distances along a ray at which the ray intersects an axis-aligned box
-// See https://tavianator.com/2011/ray_box.html
-RayShapeIntersection intersectBox(in Ray ray, in Box box)
+RayShapeIntersection intersectBox(in Ray ray, in vec3 minBound, in vec3 maxBound)
 {
     // Consider the box as the intersection of the space between 3 pairs of parallel planes
     // Compute the distance along the ray to each plane
-    vec3 t0 = (box.p0 - ray.pos) * ray.dInv;
-    vec3 t1 = (box.p1 - ray.pos) * ray.dInv;
+    vec3 t0 = (minBound - ray.pos) / ray.dir;
+    vec3 t1 = (maxBound - ray.pos) / ray.dir;
 
     // Identify candidate entries/exits based on distance from ray.pos
     vec3 entries = min(t0, t1);
     vec3 exits = max(t0, t1);
 
-    // The actual box intersection points are the furthest entry and the closest exit
-    float entryT = max(max(entries.x, entries.y), entries.z);
-    float exitT = min(min(exits.x, exits.y), exits.z);
+    vec3 directions = sign(ray.dir);
+
+    // The actual intersection points are the furthest entry and the closest exit
+    float lastEntry = maxComponent(entries);
+    bvec3 isLastEntry = equal(entries, vec3(lastEntry));
+    vec3 entryNormal = -1.0 * vec3(isLastEntry) * directions;
+    vec4 entry = vec4(entryNormal, lastEntry);
 
-    vec3 entryNormal = getBoxNormal(box, ray, entryT - RAY_SHIFT);
-    vec3 exitNormal = getBoxNormal(box, ray, exitT + RAY_SHIFT);
+    float firstExit = minComponent(exits);
+    bvec3 isFirstExit = equal(exits, vec3(firstExit));
+    vec3 exitNormal = vec3(isLastEntry) * directions;
+    vec4 exit = vec4(exitNormal, firstExit);
 
-    if (entryT > exitT) {
-        entryT = NO_HIT;
-        exitT = NO_HIT;
+    if (entry.w > exit.w) {
+        entry.w = NO_HIT;
+        exit.w = NO_HIT;
     }
 
-    return RayShapeIntersection(vec4(entryNormal, entryT), vec4(exitNormal, exitT));
+    return RayShapeIntersection(entry, exit);
 }
 
 void intersectShape(in Ray ray, inout Intersections ix)
 {
-    RayShapeIntersection intersection = intersectBox(ray, Box(u_renderMinBounds, u_renderMaxBounds));
+    RayShapeIntersection intersection = intersectBox(ray, u_renderMinBounds, u_renderMaxBounds);
     setShapeIntersection(ix, BOX_INTERSECTION_INDEX, intersection);
 }
diff --git a/packages/engine/Source/Shaders/Voxels/IntersectionUtils.glsl b/packages/engine/Source/Shaders/Voxels/IntersectionUtils.glsl
@@ -4,16 +4,6 @@
 
 #define NO_HIT (-czm_infinity)
 #define INF_HIT (czm_infinity * 0.5)
-#define RAY_SHIFT (0.000003163)
-#define RAY_SCALE (1.003163)
-
-struct Ray {
-    vec3 pos;
-    vec3 dir;
-#if defined(SHAPE_BOX)
-    vec3 dInv;
-#endif
-};
 
 struct RayShapeIntersection {
     vec4 entry;

diff --git a/packages/engine/Source/Shaders/Voxels/Octree.glsl b/packages/engine/Source/Shaders/Voxels/Octree.glsl
@@ -79,7 +79,7 @@ int getOctreeParentIndex(in int octreeIndex) {
 */
 vec3 getTileUv(in vec3 shapePosition, in ivec4 octreeCoords) {
 	// PERFORMANCE_IDEA: use bit-shifting (only in WebGL2)
-    float dimAtLevel = pow(2.0, float(octreeCoords.w));
+    float dimAtLevel = exp2(float(octreeCoords.w));
     return shapePosition * dimAtLevel - vec3(octreeCoords.xyz);
 }
 
@@ -126,7 +126,7 @@ void getOctreeLeafSampleDatas(in OctreeNodeData data, in ivec4 octreeCoords, out
 #endif
 
 OctreeNodeData traverseOctreeDownwards(in vec3 shapePosition, inout TraversalData traversalData) {
-    float sizeAtLevel = 1.0 / pow(2.0, float(traversalData.octreeCoords.w));
+    float sizeAtLevel = exp2(-1.0 * float(traversalData.octreeCoords.w));
     vec3 start = vec3(traversalData.octreeCoords.xyz) * sizeAtLevel;
     vec3 end = start + vec3(sizeAtLevel);
     OctreeNodeData childData;