private void AddLight(SpotLight spotLight)
        {
            device.SetRenderTarget(shadingTarget);
            device.BlendState = BlendState.Additive;
            effect2Lights.CurrentTechnique = effect2Lights.Techniques["DeferredSpotLight"];
            effect2Lights.Parameters["xNormalMap"].SetValue(normalMap);
            effect2Lights.Parameters["xDepthMap"].SetValue(depthMap);
            effect2Lights.Parameters["xShadowMap"].SetValue(shadowMap);

            effect2Lights.Parameters["xLightPosition"].SetValue(spotLight.Position);
            effect2Lights.Parameters["xLightStrength"].SetValue(spotLight.Strength);
            effect2Lights.Parameters["xConeDirection"].SetValue(spotLight.Direction);
            effect2Lights.Parameters["xConeAngle"].SetValue(spotLight.ConeAngle);
            effect2Lights.Parameters["xConeDecay"].SetValue(spotLight.ConeDecay);

            Matrix viewProjInv = Matrix.Invert(fpsCam.ViewMatrix * fpsCam.ProjectionMatrix);
            effect2Lights.Parameters["xViewProjectionInv"].SetValue(viewProjInv);
            effect2Lights.Parameters["xLightViewProjection"].SetValue(spotLight.ViewMatrix * spotLight.ProjectionMatrix);

            foreach (EffectPass pass in effect2Lights.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.DrawUserPrimitives<VertexPositionTexture>(PrimitiveType.TriangleStrip, fsVertices, 0, 2);
            }
            device.SetRenderTarget(null);
        }