Only rebuild shaders on sky rotation change if changing away from ide…

…ntity (#5467)

* Only rebuild shaders on sky rotation change if changing away from identity

* update based on comment

* lint

---------

Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>

src/scene/materials/standard-material-options-builder.js

@@ -1,5 +1,3 @@
-import { Quat } from '../../core/math/quat.js';
-
 import {
     PIXELFORMAT_DXT5, PIXELFORMAT_RGBA8, TEXTURETYPE_SWIZZLEGGGR
 } from '../../platform/graphics/constants.js';
@@ -352,7 +350,7 @@ class StandardMaterialOptionsBuilder {
 
         // TODO: add a test for if non skybox cubemaps have rotation (when this is supported) - for now assume no non-skybox cubemap rotation
         options.litOptions.skyboxIntensity = usingSceneEnv && (scene.skyboxIntensity !== 1 || scene.physicalUnits);
-        options.litOptions.useCubeMapRotation = usingSceneEnv && scene.skyboxRotation && !scene.skyboxRotation.equals(Quat.IDENTITY);
+        options.litOptions.useCubeMapRotation = usingSceneEnv && scene._skyboxRotationShaderInclude;
     }
 
     _updateLightOptions(options, scene, stdMat, objDefs, sortedLights, staticLightList) {

src/scene/scene.js

@@ -226,6 +226,7 @@ class Scene extends EventHandler {
         this._skyboxLuminance = 0;
         this._skyboxMip = 0;
 
+        this._skyboxRotationShaderInclude = false;
         this._skyboxRotation = new Quat();
         this._skyboxRotationMat3 = new Mat3();
         this._skyboxRotationMat4 = new Mat4();
@@ -626,14 +627,22 @@ class Scene extends EventHandler {
      */
     set skyboxRotation(value) {
         if (!this._skyboxRotation.equals(value)) {
+
+            const isIdentity = value.equals(Quat.IDENTITY);
             this._skyboxRotation.copy(value);
-            if (value.equals(Quat.IDENTITY)) {
+
+            if (isIdentity) {
                 this._skyboxRotationMat3.setIdentity();
             } else {
                 this._skyboxRotationMat4.setTRS(Vec3.ZERO, value, Vec3.ONE);
                 this._skyboxRotationMat4.invertTo3x3(this._skyboxRotationMat3);
             }
-            this._resetSky();
+
+            // only reset sky / rebuild scene shaders if rotation changed away from identity for the first time
+            if (!this._skyboxRotationShaderInclude && !isIdentity) {
+                this._skyboxRotationShaderInclude = true;
+                this._resetSky();
+            }
         }
     }