Feature CPU optimizations

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipeline.cs

             {
                 CommandBuffer cmd = CommandBufferPool.Get("Collect Shadows");
 
-                //Keywords and constants should be set up in advance for the collect pass.
+                //Keywords and constants are set up in advance for the collect pass.
-                SetShaderKeywords(cmd, ref lightData, visibleLights);
+                SetMainLightShaderKeywords(cmd, ref lightData, visibleLights);
 
                 cmd.GetTemporaryRT(m_ScreenSpaceShadowMapRTID, m_CurrCamera.pixelWidth, m_CurrCamera.pixelHeight, 0, FilterMode.Bilinear, RenderTextureFormat.R8);
                 cmd.Blit(null, m_ScreenSpaceShadowMapRT, m_ScreenSpaceShadowsMaterial);
             // Main light has an optimized shader path for main light. This will benefit games that only care about a single light.
             // Lightweight pipeline also supports only a single shadow light, if available it will be the main light.
             SetupMainLightConstants(cmd, lights, lightData.mainLightIndex);
-            if (lightData.shadowMapSampleType != LightShadows.None)
+            if (lightData.shadowMapSampleType != LightShadows.None && !m_RequireScreenSpaceShadows)
                 SetupShadowReceiverConstants(cmd, lights[lightData.mainLightIndex]);
 
             SetupAdditionalListConstants(cmd, lights, ref lightData);
             cmd.SetGlobalVector(ShadowConstantBuffer._ShadowOffset2, new Vector4(-invHalfShadowResolution,  invHalfShadowResolution, 0.0f, 0.0f));
             cmd.SetGlobalVector(ShadowConstantBuffer._ShadowOffset3, new Vector4( invHalfShadowResolution,  invHalfShadowResolution, 0.0f, 0.0f));
             cmd.SetGlobalVector(ShadowConstantBuffer._ShadowmapSize, new Vector4(invShadowResolution, invShadowResolution, m_Asset.ShadowAtlasResolution, m_Asset.ShadowAtlasResolution));
-            cmd.SetGlobalVectorArray(ShadowConstantBuffer._FrustumCorners, LightweightUtils.GetFarPlaneCorners(m_CurrCamera));
+            cmd.SetGlobalVectorArray(ShadowConstantBuffer._FrustumCorners, m_RequireScreenSpaceShadows ? LightweightUtils.GetFarPlaneCorners(m_CurrCamera) : new Vector4[4] );
+
+            if(!m_RequireScreenSpaceShadows) 
+                SetMainLightShaderKeywords(cmd, ref lightData, visibleLights);
+
+            CoreUtils.SetKeyword(cmd, "_ADDITIONAL_LIGHTS", lightData.totalAdditionalLightsCount > 0);
+            CoreUtils.SetKeyword(cmd, "_MIXED_LIGHTING_SUBTRACTIVE", m_MixedLightingSetup == MixedLightingSetup.Subtractive);
+            CoreUtils.SetKeyword(cmd, "_VERTEX_LIGHTS", vertexLightsCount > 0);
+            CoreUtils.SetKeyword(cmd, "SOFTPARTICLES_ON", m_RequireDepthTexture && m_Asset.RequireSoftParticles);
+           
+            bool linearFogModeEnabled = false;
+            bool exponentialFogModeEnabled = false;
+            if (RenderSettings.fog)
+            {
+                if (RenderSettings.fogMode == FogMode.Linear)
+                    linearFogModeEnabled = true;
+                else
+                    exponentialFogModeEnabled = true;
+            }
+
+            CoreUtils.SetKeyword(cmd, "FOG_LINEAR", linearFogModeEnabled);
+            CoreUtils.SetKeyword(cmd, "FOG_EXP2", exponentialFogModeEnabled);
+        }
+
+        private void SetMainLightShaderKeywords(CommandBuffer cmd, ref LightData lightData, List<VisibleLight> visibleLights)
+        {
             int mainLightIndex = lightData.mainLightIndex;
 
             for (int i = 0; i < kMainLightKeywords.Length; ++i)
             }
 
             CoreUtils.SetKeyword(cmd, "_MAIN_LIGHT_COOKIE", mainLightIndex != -1 && LightweightUtils.IsSupportedCookieType(visibleLights[mainLightIndex].lightType) && visibleLights[mainLightIndex].light.cookie != null);
-            CoreUtils.SetKeyword(cmd, "_ADDITIONAL_LIGHTS", lightData.totalAdditionalLightsCount > 0);
-            CoreUtils.SetKeyword(cmd, "_MIXED_LIGHTING_SUBTRACTIVE", m_MixedLightingSetup == MixedLightingSetup.Subtractive);
-            CoreUtils.SetKeyword(cmd, "_VERTEX_LIGHTS", vertexLightsCount > 0);
-            CoreUtils.SetKeyword(cmd, "SOFTPARTICLES_ON", m_RequireDepthTexture && m_Asset.RequireSoftParticles);
-           
-            bool linearFogModeEnabled = false;
-            bool exponentialFogModeEnabled = false;
-            if (RenderSettings.fog)
-            {
-                if (RenderSettings.fogMode == FogMode.Linear)
-                    linearFogModeEnabled = true;
-                else
-                    exponentialFogModeEnabled = true;
-            }
-
-            CoreUtils.SetKeyword(cmd, "FOG_LINEAR", linearFogModeEnabled);
-            CoreUtils.SetKeyword(cmd, "FOG_EXP2", exponentialFogModeEnabled);
         }
 
         private bool RenderShadows(ref CullResults cullResults, ref VisibleLight shadowLight, int shadowLightIndex, ref ScriptableRenderContext context)