fix cookie coord for point light

fix cookie coord for point light

Assets/ScriptableRenderLoop/fptl/FptlLighting.cs

 					boundData[i].vScaleXY = new Vec2(1.0f, 1.0f);
 					boundData[i].fRadius = range;
 
-					// represents a left hand coordinate system in world space
+                    // represents a left hand coordinate system in world space since det(worldToView)<0
 					Matrix4x4 lightToView = worldToView * lightToWorld;
 					Vector3 vx = lightToView.GetColumn(0);
 					Vector3 vy = lightToView.GetColumn(1);

Assets/ScriptableRenderLoop/fptl/Internal-DeferredShading.shader

 			float atten = tex2Dlod(_LightTextureB0, float4(attLookUp.rr, 0.0, 0.0)).UNITY_ATTEN_CHANNEL;
 
 			float4 cookieColor = float4(1,1,1,1);
-
-			float3 cookieCoord = float3(dot(vL, lgtDat.vLaxisX.xyz), dot(vL, lgtDat.vLaxisY.xyz), -dot(vL, lgtDat.vLaxisZ.xyz));
+				float3 cookieCoord = -float3(dot(vL, lgtDat.vLaxisX.xyz), dot(vL, lgtDat.vLaxisY.xyz), dot(vL, lgtDat.vLaxisZ.xyz));	// negate to make vL a fromLight vector
 				cookieColor = UNITY_SAMPLE_TEXCUBEARRAY_LOD(_pointCookieTextures, float4(cookieCoord, lgtDat.iSliceIndex), 0.0);
 				atten *= cookieColor.w;
 			}