D3D延迟着色简单实现

延迟着色有别于以前的流程，光照信息不在固定管线第一阶段或VS里面计算，而是在PS里面计算。目的就是为了提高性能，一个是在3D空间计算，一个是在2D空间计算

分两步

一 把位置，发现，材质等信息渲染到纹理，纹理需要创建浮点型的。这一步需要利用d3d多渲染目标

float4x4 matWorld;
float4x4 matViewProjection;

struct VS_INPUT 
{
   float3 Pos:     POSITION;
   float3 Normal:  NORMAL;
};

struct VS_OUTPUT 
{
   float4 Pos:            POSITION;
   float3 PosInWorld:     TEXCOORD0; 
   float3 NormalInWorld:  TEXCOORD1;
};

VS_OUTPUT vs_main( VS_INPUT In )
{
   VS_OUTPUT Out;

   Out.Pos           = mul(float4(In.Pos,1.0),matViewProjection );
   Out.PosInWorld    = mul(float4(In.Pos,1.0),matWorld);
   Out.NormalInWorld = mul(In.Normal,matWorld);

   return Out;
}

struct PS_INPUT 
{
   float3 PosInWorld:     TEXCOORD0; 
   float3 NormalInWorld:  TEXCOORD1;
};

struct PS_OUTPUT 
{
   float4 PosInWorld    : COLOR0;
   float4 NormalInWorld : COLOR1;
};

PS_OUTPUT ps_main( PS_INPUT In )
{
   PS_OUTPUT Out;
   
   Out.PosInWorld    = float4(In.PosInWorld,1.0);
   Out.NormalInWorld = float4(In.NormalInWorld,1.0);
   
   return Out;
}

二 计算光照信息

float4x4 matWorld;
float4x4 matViewProjection;

struct VS_INPUT 
{
   float3 Pos:     POSITION;
};

struct VS_OUTPUT 
{
   float4 Pos:            POSITION;
   float2 TexCoord:       TEXCOORD0; 
};

VS_OUTPUT vs_main( VS_INPUT In )
{
   VS_OUTPUT Out;

   Out.Pos           = float4(sign(In.Pos.xy),0.0,1.0);
   Out.TexCoord.x    = (Out.Pos.x+1.0) * 0.5;
   Out.TexCoord.y    = 1.0 - ((Out.Pos.y+1.0) * 0.5);

   return Out;
}

float4 ObjColor;
float4 ClearColor;
float3 LightPos;

sampler2D PosMap;
sampler2D NormalMap;

struct PS_INPUT 
{
   float2 TexCoord:       TEXCOORD0; 
};

struct PS_OUTPUT 
{
   float4 Color    : COLOR0;
};

PS_OUTPUT ps_main( PS_INPUT In )
{
   PS_OUTPUT Out;

   float4 pos    = tex2D(PosMap,In.TexCoord);   

   if (pos.w==0.0) // If nothing is drawn at this pixel, just output clear color
   {
      Out.Color = ClearColor;
   } // End if
   else
   {
      float3 normal  = normalize(tex2D(NormalMap,In.TexCoord).xyz);     
      float3 toLight = normalize(LightPos - pos.xyz);
   
      float diffuse = dot(normal,toLight);
   
      Out.Color = ObjColor * diffuse;
   } // End else
   
   return Out;
}