[Fix] Fix the bounding sphere calculation for spot lights (#4800)

* [Fix] Fix the bounding sphere calculation for spot lights

* lint

* small improvement

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

src/scene/light.js

@@ -15,8 +15,6 @@ import {
 } from './constants.js';
 import { ShadowRenderer } from './renderer/shadow-renderer.js';
 
-const spotCenter = new Vec3();
-const spotEndPoint = new Vec3();
 const tmpVec = new Vec3();
 const tmpBiases = {
     bias: 0,
@@ -158,7 +156,7 @@ class Light {
         this._position = new Vec3(0, 0, 0);
         this._direction = new Vec3(0, 0, 0);
         this._innerConeAngleCos = Math.cos(this._innerConeAngle * Math.PI / 180);
-        this._outerConeAngleCos = Math.cos(this._outerConeAngle * Math.PI / 180);
+        this._updateOuterAngle(this._outerConeAngle);
 
         this._usePhysicalUnits = undefined;
 
@@ -416,7 +414,8 @@ class Light {
             return;
 
         this._outerConeAngle = value;
-        this._outerConeAngleCos = Math.cos(value * Math.PI / 180);
+        this._updateOuterAngle(value);
+
         if (this._usePhysicalUnits) {
             this._updateFinalColor();
         }
@@ -426,6 +425,12 @@ class Light {
         return this._outerConeAngle;
     }
 
+    _updateOuterAngle(angle) {
+        const radAngle = angle * Math.PI / 180;
+        this._outerConeAngleCos = Math.cos(radAngle);
+        this._outerConeAngleSin = Math.sin(radAngle);
+    }
+
     set intensity(value) {
         if (this._intensity !== value) {
             this._intensity = value;
@@ -713,24 +718,23 @@ class Light {
 
     getBoundingSphere(sphere) {
         if (this._type === LIGHTTYPE_SPOT) {
-            const range = this.attenuationEnd;
+
+            // based on https://bartwronski.com/2017/04/13/cull-that-cone/
+            const size = this.attenuationEnd;
             const angle = this._outerConeAngle;
-            const f = Math.cos(angle * math.DEG_TO_RAD);
+            const cosAngle = this._outerConeAngleCos;
             const node = this._node;
+            tmpVec.copy(node.up);
 
-            spotCenter.copy(node.up);
-            spotCenter.mulScalar(-range * 0.5 * f);
-            spotCenter.add(node.getPosition());
-            sphere.center = spotCenter;
-
-            spotEndPoint.copy(node.up);
-            spotEndPoint.mulScalar(-range);
-
-            tmpVec.copy(node.right);
-            tmpVec.mulScalar(Math.sin(angle * math.DEG_TO_RAD) * range);
-            spotEndPoint.add(tmpVec);
+            if (angle > 45) {
+                sphere.radius = size * this._outerConeAngleSin;
+                tmpVec.mulScalar(-size * cosAngle);
+            } else {
+                sphere.radius = size / (2 * cosAngle);
+                tmpVec.mulScalar(-sphere.radius);
+            }
 
-            sphere.radius = spotEndPoint.length() * 0.5;
+            sphere.center.add2(node.getPosition(), tmpVec);
 
         } else if (this._type === LIGHTTYPE_OMNI) {
             sphere.center = this._node.getPosition();