Atmosphere addon fixes for floating origin (#17378)

- Ensure atmosphere parameters get computed correctly when floating
origin is enabled, assuming planet center is 0,0,0 in world space.
- Use common dot product helper
- **NOTE:** Minor breaking change to API; Include `Camera` as parameter
to some existing observables that were previously `Observable<void>`.

Author: kircher1

packages/dev/addons/src/atmosphere/atmosphere.ts

@@ -137,12 +137,12 @@ export class Atmosphere implements IDisposable {
     /**
      * Called before the LUTs are rendered for this camera. This happens after the per-camera UBO update.
      */
-    public readonly onBeforeRenderLutsForCameraObservable = new Observable<void>();
+    public readonly onBeforeRenderLutsForCameraObservable = new Observable<Camera>();
 
     /**
      * Called after the LUTs were rendered.
      */
-    public readonly onAfterRenderLutsForCameraObservable = new Observable<void>();
+    public readonly onAfterRenderLutsForCameraObservable = new Observable<Camera>();
 
     /**
      * If provided, this is the depth texture used for composition passes.
@@ -734,7 +734,7 @@ export class Atmosphere implements IDisposable {
         // Before rendering, make sure the per-camera variables have been updated.
         this._onBeforeCameraRenderObserver = scene.onBeforeCameraRenderObservable.add((x) => {
             this._updatePerCameraVariables(x);
-            this._renderLutsForCamera();
+            this._renderLutsForCamera(x);
         });
 
         {
@@ -1207,8 +1207,9 @@ export class Atmosphere implements IDisposable {
     /**
      * Renders the lookup tables, some of which can vary per-camera.
      * It is expected that updatePerCameraVariables was previously called.
+     * @param camera - The camera to render the LUTs for.
      */
-    private _renderLutsForCamera(): void {
+    private _renderLutsForCamera(camera: Camera): void {
         {
             this.onBeforeLightVariablesUpdateObservable.notifyObservers();
 
@@ -1228,7 +1229,7 @@ export class Atmosphere implements IDisposable {
         // Render the LUTs.
         const isEnabled = this.isEnabled();
         {
-            this.onBeforeRenderLutsForCameraObservable.notifyObservers();
+            this.onBeforeRenderLutsForCameraObservable.notifyObservers(camera);
 
             // After UBO update we can render the global LUTs which use some of these values on the GPU.
             // TODO: Could break out update and UBOs to global vs. per-camera.
@@ -1254,7 +1255,7 @@ export class Atmosphere implements IDisposable {
                 }
             }
 
-            this.onAfterRenderLutsForCameraObservable.notifyObservers();
+            this.onAfterRenderLutsForCameraObservable.notifyObservers(camera);
         }
     }
 

packages/dev/addons/src/atmosphere/atmospherePBRMaterialPlugin.ts

@@ -152,6 +152,9 @@ export class AtmospherePBRMaterialPlugin extends MaterialPluginBase {
             this._atmosphere.bindUniformBufferToEffect(effect);
         }
 
+        // Need the offset to apply which will take a world space position and convert it to a global space position in the atmosphere.
+        // If floating origin mode is enabled, that offset is the floating origin offset.
+        // If not, it's an offset up the Y-axis by the planet radius.
         uniformBuffer.updateVector3(
             OriginOffsetUniformName,
             scene.floatingOriginMode

packages/dev/addons/src/atmosphere/atmospherePerCameraVariables.ts

@@ -86,13 +86,18 @@ export class AtmospherePerCameraVariables {
 
     /**
      * The camera position in global space kilometers.
+     *
+     * The behavior of this value depends on whether floating origin mode is enabled:
+     * - If floating origin mode is enabled, this is simply the camera's global position scaled to kilometers. The atmosphere's origin height is used to offset the camera position along its geocentric normal.
+     * - If floating origin mode is disabled, the camera's y position is offset by the planet radius plus any origin height.
      */
     public get cameraPositionGlobal(): IVector3Like {
         return this._cameraPositionGlobal;
     }
 
     /**
      * The camera position, clamped to the planet radius offset, in global space kilometers.
+     * See {@link cameraPositionGlobal} for details on how the value is computed.
      */
     public get clampedCameraPositionGlobal(): IVector3Like {
         return this._clampedCameraPositionGlobal;
@@ -114,6 +119,7 @@ export class AtmospherePerCameraVariables {
 
     /**
      * The geocentric normal of the camera in global space i.e., the normalization of {@link cameraPositionGlobal}.
+     * Note the behavior of this value depends on whether floating origin mode is enabled. See {@link cameraPositionGlobal} for details.
      */
     public get cameraGeocentricNormal(): IVector3Like {
         return this._cameraGeocentricNormal;
@@ -160,37 +166,51 @@ export class AtmospherePerCameraVariables {
         this._cameraNearPlane = camera.minZ;
         this._cameraForward.copyFrom(camera.getForwardRayToRef(TempRay, 1).direction);
 
-        const engine = camera.getScene().getEngine();
+        const scene = camera.getScene();
+        const engine = scene.getEngine();
         this._viewport.copyFromFloats(0.0, 0.0, engine.getRenderWidth(), engine.getRenderHeight());
 
         // Compute inverse view projection matrix, but remove the translational component to increase precision.
         const viewMatrix = camera.getViewMatrix();
         const projectionMatrix = camera.getProjectionMatrix();
-        if (!this._lastViewMatrix.equals(viewMatrix) || !this._lastProjectionMatrix.equals(projectionMatrix)) {
-            this._lastViewMatrix.copyFrom(viewMatrix);
-            this._lastViewMatrix.setTranslation(Vector3.ZeroReadOnly);
-            this._lastViewMatrix.invertToRef(this._inverseViewMatrixWithoutTranslation);
-
-            this._lastProjectionMatrix.copyFrom(projectionMatrix);
-            this._lastProjectionMatrix.invertToRef(this._inverseProjectionMatrix);
+        const lastViewMatrix = this._lastViewMatrix;
+        const lastProjectionMatrix = this._lastProjectionMatrix;
+        if (!lastViewMatrix.equals(viewMatrix) || !lastProjectionMatrix.equals(projectionMatrix)) {
+            lastViewMatrix.copyFrom(viewMatrix);
+            lastViewMatrix.setTranslation(Vector3.ZeroReadOnly);
+            lastViewMatrix.invertToRef(this._inverseViewMatrixWithoutTranslation);
+
+            lastProjectionMatrix.copyFrom(projectionMatrix);
+            lastProjectionMatrix.invertToRef(this._inverseProjectionMatrix);
             this._inverseProjectionMatrix.multiplyToRef(this._inverseViewMatrixWithoutTranslation, this._inverseViewProjectionMatrixWithoutTranslation);
         }
 
         // Compute the global space position of the camera in kilometers.
-        this._cameraPosition.copyFrom(camera.globalPosition);
-        this._cameraPosition.scaleToRef(1.0 / 1000.0, this._cameraPositionGlobal);
-        this._cameraPositionGlobal.y += planetRadius + originHeight;
-        this._cameraHeight = this._cameraPositionGlobal.y - planetRadius;
+        const cameraPositionGlobal = this._cameraPosition.copyFrom(camera.globalPosition).scaleToRef(0.001, this._cameraPositionGlobal); // scale to kilometers
+
+        // Apply the origin height to the camera position, and in doing so, compute the camera geocentric normal.
+        if (scene.floatingOriginMode) {
+            // When in floating origin mode, assume world space origin is at the planet center.
+            // Therefore "up" is away from the planet center (0, 0, 0).
+            cameraPositionGlobal.normalizeToRef(this._cameraGeocentricNormal);
+            this._cameraGeocentricNormal.scaleAndAddToRef(originHeight, cameraPositionGlobal);
+        } else {
+            // If not in floating origin mode, offset the camera position by the origin height.
+            // Assume the origin is directly above the planet surface along the up axis (y axis).
+            cameraPositionGlobal.y += planetRadius + originHeight;
+            cameraPositionGlobal.normalizeToRef(this._cameraGeocentricNormal);
+        }
+
+        this._cameraRadius = cameraPositionGlobal.length(); // distance from planet center
+        this._cameraHeight = this._cameraRadius - planetRadius; // height above planet surface
 
         // Clamp the camera parameters.
-        this._cameraRadius = this._cameraPositionGlobal.length();
         this._clampedCameraRadius = this._cameraRadius;
-        this._cameraPositionGlobal.normalizeToRef(this._cameraGeocentricNormal);
         if (this._clampedCameraRadius < planetRadiusWithOffset) {
             this._clampedCameraRadius = planetRadiusWithOffset;
             this._cameraGeocentricNormal.scaleToRef(planetRadiusWithOffset, this._clampedCameraPositionGlobal);
         } else {
-            this._clampedCameraPositionGlobal.copyFrom(this._cameraPositionGlobal);
+            this._clampedCameraPositionGlobal.copyFrom(cameraPositionGlobal);
         }
 
         this._cosCameraHorizonAngleFromZenith = ComputeCosHorizonAngleFromZenith(planetRadius, this._clampedCameraRadius);

packages/dev/addons/src/atmosphere/diffuseSkyIrradianceLut.ts

@@ -11,6 +11,7 @@ import type { IColor3Like, IColor4Like, IVector2Like, IVector3Like } from "core/
 import type { Nullable } from "core/types";
 import { RenderTargetTexture } from "core/Materials/Textures/renderTargetTexture";
 import { Sample2DRgbaToRef } from "./sampling";
+import { Vector3Dot } from "core/Maths/math.vector.functions";
 import "./Shaders/diffuseSkyIrradiance.fragment";
 import "./Shaders/fullscreenTriangle.vertex";
 
@@ -161,7 +162,7 @@ export class DiffuseSkyIrradianceLut {
             return result;
         }
 
-        const cosAngleLightToZenith = directionToLight.x * cameraGeocentricNormal.x + directionToLight.y * cameraGeocentricNormal.y + directionToLight.z * cameraGeocentricNormal.z;
+        const cosAngleLightToZenith = Vector3Dot(directionToLight, cameraGeocentricNormal);
         ComputeLutUVToRef(properties, radius, cosAngleLightToZenith, UvTemp);
         Sample2DRgbaToRef(UvTemp.x, UvTemp.y, LutWidthPx, LutHeightPx, this._lutData, Color4Temp, FromHalfFloat);
 

packages/dev/addons/src/atmosphere/transmittanceLut.ts

@@ -13,6 +13,7 @@ import type { Nullable } from "core/types";
 import { Observable } from "core/Misc/observable";
 import { RenderTargetTexture } from "core/Materials/Textures/renderTargetTexture";
 import { Sample2DRgbaToRef } from "./sampling";
+import { Vector3Dot } from "core/Maths/math.vector.functions";
 import "./Shaders/fullscreenTriangle.vertex";
 import "./Shaders/transmittance.fragment";
 
@@ -162,8 +163,7 @@ export class TransmittanceLut {
      */
     public getTransmittedColorToRef<T extends IColor3Like>(directionToLight: IVector3Like, pointRadius: number, pointGeocentricNormal: IVector3Like, result: T): T {
         if (this._lutData[0] !== undefined) {
-            const cosAngleLightToZenith =
-                directionToLight.x * pointGeocentricNormal.x + directionToLight.y * pointGeocentricNormal.y + directionToLight.z * pointGeocentricNormal.z;
+            const cosAngleLightToZenith = Vector3Dot(directionToLight, pointGeocentricNormal);
             SampleLutToRef(this._atmosphere.physicalProperties, this._lutData, pointRadius, cosAngleLightToZenith, Color4Temp);
             result.r = Color4Temp.r;
             result.g = Color4Temp.g;