Deferred Rendering - Practical Rendering and Computation with Direct3D 11 - page 505

Since DiffuseLight and SpecularLight each have 3 components, storing the full val-
ues in our light buffer would require storing 6 individual floating-point values. This would
require writing to at least two render targets simultaneously, which is often not optimal
from a performance and memory-consumption point of view. Thus, a common optimiza-
tion is to store only the specular intensity rather than the color, which allows the light buffer
to consist of a single 4-component texture. This approach is taken in the lighting shader
code in Listing 11.5.

// Textures
Texture2D NormalTexture : register( t0 );

Texture2D PositionTexture : register( t1 );

// Constants
cbuffer LightParams
{

float3 LightPos;
float3 LightColor;
float3 LightDirection;
float2 SpotlightAngles;
float4 LightRange;

};

cbuffer CameraParams
{

float3 CameraPos;

}

// Vertex shader for lighting pass of light prepass deferred rendering
fioat4 VSMain( in float4 Position : POSITION ) : SV_Position
{

// Just pass along the position of the full-screen quad
return Position;

}
// Helper function for extracting G-Buffer attributes
void GetGBufferAttributes( in fioat2 screenPos, out float3 normal,
out float3 position, out float specularPower )

{

// Determine our indices for sampling the texture based on the current
// screen position
int3 samplelndices = int3( screenPos. xy, 0 );

float4 normalTex = NormalTexture. Load ( samplelndices );
normal = normalTex.xyz;
specularPower = normalTex.w;
position = PositionTexture. Load ( samplelndices ).xyz;

}

// Calculates the lighting term for a single G-Buffer texel
float4 CalcLighting( in float3 normal, in float3 position, in float specularPower )