D3D HLSL 一段代码注释

// FixedFuncEMU.fx
// Copyright (c) 2005 Microsoft Corporation. All rights reserved.
//

struct VSSceneIn
{
float3 pos : POSITION; //position of the particle
float3 norm : NORMAL; //velocity of the particle
float2 tex : TEXTURE0; //tex coords
};

struct VSSceneOut
{
float4 pos : SV_Position; //position
float2 tex : TEXTURE0; //texture coordinate
float3 wPos : TEXTURE1; //world space pos
float3 wNorm : TEXTURE2; //world space normal
float4 colorD : COLOR0; //color for gouraud and flat shading
float4 colorS : COLOR1; //color for specular
float fogDist : FOGDISTANCE; //distance used for fog calculations
float3 planeDist : SV_ClipDistance0; //clip distance for 3 planes
};

struct PSSceneIn
{
float4 pos : SV_Position; //position
float2 tex : TEXTURE0; //texture coordinate
float3 wPos : TEXTURE1; //world space pos
float3 wNorm : TEXTURE2; //world space normal
float4 colorD : COLOR0; //color for gouraud and flat shading
float4 colorS : COLOR1; //color for specular
float fogDist : FOGDISTANCE; //distance used for fog calculations
};

struct Light
{
float4 Position;
float4 Diffuse;
float4 Specular;
float4 Ambient;
float4 Atten;
};

#define FOGMODE_NONE 0
#define FOGMODE_LINEAR 1
#define FOGMODE_EXP 2
#define FOGMODE_EXP2 3
#define E 2.71828

cbuffer cbLights
{
float4 g_clipplanes[3];
Light g_lights[8];
};

cbuffer cbPerFrame
{
float4x4 g_mWorld;
float4x4 g_mView;
float4x4 g_mProj;
float4x4 g_mInvProj;
float4x4 g_mLightViewProj;
};

cbuffer cbPerTechnique
{
bool g_bEnableLighting = true;
bool g_bEnableClipping = true;
bool g_bPointScaleEnable = false;
float g_pointScaleA;
float g_pointScaleB;
float g_pointScaleC;
float g_pointSize;

//fog params
int g_fogMode = FOGMODE_NONE;
float g_fogStart;
float g_fogEnd;
float g_fogDensity;
float4 g_fogColor;
};

cbuffer cbPerViewChange
{
//viewport params
float g_viewportHeight;
float g_viewportWidth;
float g_nearPlane;
};

cbuffer cbImmutable
{
float3 g_positions[4] =
{
float3( -0.5, 0.5, 0 ),
float3( 0.5, 0.5, 0 ),
float3( -0.5, -0.5, 0 ),
float3( 0.5, -0.5, 0 ),
};
};

Texture2D g_txDiffuse;
Texture2D g_txProjected;
SamplerState g_samLinear
{
Filter = MIN_MAG_MIP_LINEAR;
AddressU = Clamp;
AddressV = Clamp;
};

DepthStencilState DisableDepth
{
DepthEnable = FALSE;
DepthWriteMask = ZERO;
};

DepthStencilState EnableDepth
{
DepthEnable = TRUE;
DepthWriteMask = ALL;
};

struct ColorsOutput
{
float4 Diffuse;
float4 Specular;
};

ColorsOutput CalcLighting( float3 worldNormal, float3 worldPos, float3 cameraPos )
{
ColorsOutput output = (ColorsOutput)0.0;

for(int i=0; i<8; i++)
{
float3 toLight = g_lights[i].Position.xyz - worldPos;
float lightDist = length( toLight );
float fAtten = 1.0/dot( g_lights[i].Atten, float4(1,lightDist,lightDist*lightDist,0) );
float3 lightDir = normalize( toLight );
float3 halfAngle = normalize( normalize(-cameraPos) + lightDir );

output.Diffuse += max(0,dot( lightDir, worldNormal ) * g_lights[i].Diffuse * fAtten) + g_lights[i].Ambient;
output.Specular += max(0,pow( dot( halfAngle, worldNormal ), 64 ) * g_lights[i].Specular * fAtten );
}

return output;
}

//
// VS for emulating fixed function pipeline
//
VSSceneOut VSScenemain(VSSceneIn input)
{
VSSceneOut output = (VSSceneOut)0.0;

//output our final position in clipspace
float4 worldPos = mul( float4( input.pos, 1 ), g_mWorld );      //先对齐为float4类型，然后将模型输入的局部坐标经过左乘世界矩阵，转换为世界坐标worldPos
float4 cameraPos = mul( worldPos, g_mView ); //再将世界坐标转换为观察坐标，也是左乘。
output.pos = mul( cameraPos, g_mProj );//进行投影转换

//save world pos for later
output.wPos = worldPos;

//save the fog distance for later
output.fogDist = cameraPos.z;

//find our clipping planes (fixed function clipping is done in world space)
if( g_bEnableClipping )
{
worldPos.w = 1;

//calc the distance from the 3 clipping planes
output.planeDist.x = dot( worldPos, g_clipplanes[0] );
output.planeDist.y = dot( worldPos, g_clipplanes[1] );
output.planeDist.z = dot( worldPos, g_clipplanes[2] );
}
else
{
output.planeDist.x = 1;
output.planeDist.y = 1;
output.planeDist.z = 1;
}

//do gouraud lighting
if( g_bEnableLighting )
{
float3 worldNormal = normalize( mul( input.norm, (float3x3)g_mWorld ) );
output.wNorm = worldNormal;
ColorsOutput cOut = CalcLighting( worldNormal, worldPos, cameraPos );
output.colorD = cOut.Diffuse;
output.colorS = cOut.Specular;
}
else
{
output.colorD = float4(1,1,1,1);
}

//propogate texture coordinate
output.tex = input.tex;

return output;
}

//
// VS for rendering in screen space
//
PSSceneIn VSScreenSpacemain(VSSceneIn input)
{
PSSceneIn output = (PSSceneIn)0.0;

//output our final position
output.pos.x = (input.pos.x / (g_viewportWidth/2.0)) -1;
output.pos.y = -(input.pos.y / (g_viewportHeight/2.0)) +1;
output.pos.z = input.pos.z;
output.pos.w = 1;

//propogate texture coordinate
output.tex = input.tex;
output.colorD = float4(1,1,1,1);

return output;
}

//
// GS for flat shaded rendering
//

[maxvertexcount(3)]
void GSFlatmain( triangle VSSceneOut input[3], inout TriangleStream<VSSceneOut> FlatTriStream )
{
VSSceneOut output;

//
// Calculate the face normal
//
float3 faceEdgeA = input[1].wPos - input[0].wPos;
float3 faceEdgeB = input[2].wPos - input[0].wPos;

//
// Cross product
//
float3 faceNormal = cross(faceEdgeA, faceEdgeB);

//
//calculate the face center
//
float3 faceCenter = (input[0].wPos + input[1].wPos + input[2].wPos)/3.0;

//find world pos and camera pos
float4 worldPos = float4( faceCenter, 1 );
float4 cameraPos = mul( worldPos, g_mView );

//do shading
float3 worldNormal = normalize( faceNormal );
ColorsOutput cOut = CalcLighting( worldNormal, worldPos, cameraPos );

for(int i=0; i<3; i++)
{
output = input[i];
output.colorD = cOut.Diffuse;
output.colorS = cOut.Specular;

FlatTriStream.Append( output );
}
FlatTriStream.RestartStrip();
}

//
// GS for point rendering
//
[maxvertexcount(12)]
void GSPointmain( triangle VSSceneOut input[3], inout TriangleStream<VSSceneOut> PointTriStream )
{
VSSceneOut output;

//
// Calculate the point size
//
//float fSizeX = (g_pointSize/g_viewportWidth)/4.0;
float fSizeY = (g_pointSize/g_viewportHeight)/4.0;
float fSizeX = fSizeY;

for(int i=0; i<3; i++)
{
output = input[i];

//find world pos and camera pos
float4 worldPos = float4(input[i].wPos,1);
float4 cameraPos = mul( worldPos, g_mView );

//find our size
if( g_bPointScaleEnable )
{
float dEye = length( cameraPos.xyz );
fSizeX = fSizeY = g_viewportHeight * g_pointSize *
sqrt( 1.0f/( g_pointScaleA + g_pointScaleB*dEye + g_pointScaleC*(dEye*dEye) ) );
}

//do shading
if(g_bEnableLighting)
{
float3 worldNormal = input[i].wNorm;
ColorsOutput cOut = CalcLighting( worldNormal, worldPos, cameraPos );

output.colorD = cOut.Diffuse;
output.colorS = cOut.Specular;
}
else
{
output.colorD = float4(1,1,1,1);
}

output.tex = input[i].tex;

//
// Emit two new triangles
//
for(int i=0; i<4; i++)
{
float4 outPos = mul( worldPos, g_mView );
output.pos = mul( outPos, g_mProj );
float zoverNear = (outPos.z)/g_nearPlane;
float4 posSize = float4( g_positions[i].x*fSizeX*zoverNear,
g_positions[i].y*fSizeY*zoverNear,
0,
0 );
output.pos += posSize;

PointTriStream.Append(output);
}
PointTriStream.RestartStrip();
}
}

//
// Calculates fog factor based upon distance
//
float CalcFogFactor( float d )
{
float fogCoeff = 1.0;

if( FOGMODE_LINEAR == g_fogMode )
{
fogCoeff = (g_fogEnd - d)/(g_fogEnd - g_fogStart);
}
else if( FOGMODE_EXP == g_fogMode )
{
fogCoeff = 1.0 / pow( E, d*g_fogDensity );
}
else if( FOGMODE_EXP2 == g_fogMode )
{
fogCoeff = 1.0 / pow( E, d*d*g_fogDensity*g_fogDensity );
}

return clamp( fogCoeff, 0, 1 );
}

//
// PS for rendering with clip planes
//
float4 PSScenemain(PSSceneIn input) : SV_Target
{
//calculate the fog factor
float fog = CalcFogFactor( input.fogDist );

//calculate the color based off of the normal, textures, etc
float4 normalColor = g_txDiffuse.Sample( g_samLinear, input.tex ) * input.colorD + input.colorS;

//calculate the color from the projected texture
float4 cookieCoord = mul( float4(input.wPos,1), g_mLightViewProj );
//since we don't have texldp, we must perform the w divide ourselves befor the texture lookup
cookieCoord.xy = 0.5 * cookieCoord.xy / cookieCoord.w + float2( 0.5, 0.5 );
float4 cookieColor = float4(0,0,0,0);
if( cookieCoord.z > 0 )
cookieColor = g_txProjected.Sample( g_samLinear, cookieCoord.xy );

//for standard light-modulating effects just multiply normalcolor and coookiecolor
normalColor += cookieColor;

return fog * normalColor + (1.0 - fog)*g_fogColor;
}

//
// PS for rendering with alpha test
//
float4 PSAlphaTestmain(PSSceneIn input) : SV_Target
{
float4 color = g_txDiffuse.Sample( g_samLinear, input.tex ) * input.colorD;
if( color.a < 0.5 )
discard;
return color;
}

//
// RenderSceneGouraud - renders gouraud-shaded primitives
//
technique10 RenderSceneGouraud
{
pass p0
{
SetVertexShader( CompileShader( vs_4_0, VSScenemain() ) );
SetGeometryShader( NULL );
SetPixelShader( CompileShader( ps_4_0, PSScenemain() ) );

SetDepthStencilState( EnableDepth, 0 );
}
}

//
// RenderSceneFlat - renders flat-shaded primitives
//
technique10 RenderSceneFlat
{
pass p0
{
SetVertexShader( CompileShader( vs_4_0, VSScenemain() ) );
SetGeometryShader( CompileShader( gs_4_0, GSFlatmain() ) );
SetPixelShader( CompileShader( ps_4_0, PSScenemain() ) );

SetDepthStencilState( EnableDepth, 0 );
}
}

//
// RenderScenePoint - replaces d3dfill_point
//
technique10 RenderScenePoint
{
pass p0
{
SetVertexShader( CompileShader( vs_4_0, VSScenemain() ) );
SetGeometryShader( CompileShader( gs_4_0, GSPointmain() ) );
SetPixelShader( CompileShader( ps_4_0, PSScenemain() ) );

SetDepthStencilState( EnableDepth, 0 );
}
}

//
// RenderScreneSpace - shows how to render something in screenspace
//
technique10 RenderScreenSpaceAlphaTest
{
pass p0
{
SetVertexShader( CompileShader( vs_4_0, VSScreenSpacemain() ) );
SetGeometryShader( NULL );
SetPixelShader( CompileShader( ps_4_0, PSAlphaTestmain() ) );

SetDepthStencilState( DisableDepth, 0 );
}
}

//
// RenderScreneSpace - shows how to render something in screenspace
//
technique10 RenderTextureOnly
{
pass p0
{
SetVertexShader( CompileShader( vs_4_0, VSScenemain() ) );
SetGeometryShader( NULL );
SetPixelShader( CompileShader( ps_4_0, PSScenemain() ) );

SetDepthStencilState( EnableDepth, 0 );
}
}