Fixed issue with shadow cascade culling. (#1831)

com.unity.render-pipelines.lightweight/LWRP/LightweightShadowUtils.cs

                     cascadeIndex, shadowData.directionalLightCascadeCount, shadowData.directionalLightCascades, shadowResolution, shadowNearPlane, out viewMatrix, out projMatrix,
                     out splitData);
 
-            float cullingSphereRadius = splitData.cullingSphere.w;
-            cascadeSplitDistance.w = cullingSphereRadius * cullingSphereRadius;
-
             shadowSliceData.offsetX = (cascadeIndex % 2) * shadowResolution;
             shadowSliceData.offsetY = (cascadeIndex / 2) * shadowResolution;
             shadowSliceData.resolution = shadowResolution;

com.unity.render-pipelines.lightweight/LWRP/Passes/DirectionalShadowsPass.cs

             cmd.SetGlobalVector(DirectionalShadowConstantBuffer._DirShadowSplitSpheres1, m_CascadeSplitDistances[1]);
             cmd.SetGlobalVector(DirectionalShadowConstantBuffer._DirShadowSplitSpheres2, m_CascadeSplitDistances[2]);
             cmd.SetGlobalVector(DirectionalShadowConstantBuffer._DirShadowSplitSpheres3, m_CascadeSplitDistances[3]);
-            cmd.SetGlobalVector(DirectionalShadowConstantBuffer._DirShadowSplitSphereRadii, new Vector4(m_CascadeSplitDistances[0].w, m_CascadeSplitDistances[1].w, m_CascadeSplitDistances[2].w, m_CascadeSplitDistances[3].w));
+            cmd.SetGlobalVector(DirectionalShadowConstantBuffer._DirShadowSplitSphereRadii, new Vector4(m_CascadeSplitDistances[0].w * m_CascadeSplitDistances[0].w,
+                m_CascadeSplitDistances[1].w * m_CascadeSplitDistances[1].w,
+                m_CascadeSplitDistances[2].w * m_CascadeSplitDistances[2].w,
+                m_CascadeSplitDistances[3].w * m_CascadeSplitDistances[3].w));
             cmd.SetGlobalVector(DirectionalShadowConstantBuffer._ShadowOffset0, new Vector4(-invHalfShadowAtlasWidth, -invHalfShadowAtlasHeight, 0.0f, 0.0f));
             cmd.SetGlobalVector(DirectionalShadowConstantBuffer._ShadowOffset1, new Vector4(invHalfShadowAtlasWidth, -invHalfShadowAtlasHeight, 0.0f, 0.0f));
             cmd.SetGlobalVector(DirectionalShadowConstantBuffer._ShadowOffset2, new Vector4(-invHalfShadowAtlasWidth, invHalfShadowAtlasHeight, 0.0f, 0.0f));