#include "$ENGINE$\PerObjectData.bslinc"
#include "$ENGINE$\VertexInput.bslinc"

mixin ShadowDepthBase
{
	mixin PerObjectData;
	mixin VertexInput;

	// Render back-faces to reduce shadow acne (assuming thick geometry everywhere)
	raster
	{
		cull = cw;
	};	
	
	code
	{
		struct ShadowVStoFS
		{
			float4 position : SV_Position;
			
			#ifdef USES_GS
				float4 worldPos : TEXCOORD0;
			#else
			#ifdef USES_PS
				float shadowPos : TEXCOORD0;
			#endif
			#endif
		};
		
		cbuffer ShadowParams
		{
			float4x4 gMatViewProj;
			float2 gNDCZToDeviceZ;
			float gDepthBias;
			float gInvDepthRange;
		};
		
		/** Converts Z value from device range ([0, 1]) to NDC space. */
		float DeviceZToNDCZ(float deviceZ)
		{
			return deviceZ / gNDCZToDeviceZ.x - gNDCZToDeviceZ.y;
		}
		
		/** Converts Z value from NDC space to device Z value in range [0, 1]. */
		float NDCZToDeviceZ(float ndcZ)
		{
			return (ndcZ + gNDCZToDeviceZ.y) * gNDCZToDeviceZ.x;
		}		

		ShadowVStoFS vsmain(VertexInput_PO input)
		{
			ShadowVStoFS output;
		
			float4 worldPosition = getVertexWorldPosition(input);
			
			// If using a geometry shader, just pass through the relevant information
			// as the GS does the necessary transform and applies the depth bias
			#ifdef USES_GS
			output.worldPos = worldPosition;
			output.position = worldPosition;
			#else // USES_GS
			
			// Not using a geometry shader, transform to clip space
			float4 clipPos = mul(gMatViewProj, worldPosition);
			
			// Clamp geometry behind the near plane
			#ifdef CLAMP_TO_NEAR_PLANE
				float ndcZ = clipPos.z / clipPos.w;
				float deviceZ = NDCZToDeviceZ(ndcZ);
			
				#ifdef USES_PS
				if (deviceZ < 0)
				#else
				if (deviceZ < -gDepthBias)
				#endif
				{
					clipPos.z = DeviceZToNDCZ(0);
					clipPos.w = 1.0f;
				}
			#endif // CLAMP_TO_NEAR_PLANE

			// If using a pixel shader, output shadow depth in clip space, as
			// we'll apply bias to it in PS (depth needs to be interpolated in
			// a perspective correct way)
			#ifdef USES_PS
				output.shadowPos = clipPos.z;
			#else // Otherwise apply bias immediately
				clipPos.z = max(DeviceZToNDCZ(0), clipPos.z + gDepthBias);
			#endif // USES_PS
			
			output.position = clipPos;
			#endif // USES_GS
			
			return output;
		}
	};
};