C++博客-lucky420-随笔分类-图形学

在VS2005中，在项目编译时自动编译effect或shader

随便写写 — Tue, 22 Jan 2008 06:01:00 GMT

在项目编译时对着色器源代码进行离线编译，可以在程序运行前确定着色器程序的正确性，也可以加快程序的加载速度。

1，将effect源代码文件添加到项目中，比如是 Basic.fx
2，在Solution Explorer中选择Basic.fx，右键，选择"Properties",
3，在General页面中，选择Tool 为 “Custom Build Tool”
4，在Custom Build Step页面中，编辑Command Line为
               fxc /Tfx_2_0 /Fo$(OutDir)/$(SafeInputName).fxo $(InputFileName)
如果编写的是着色器而不是effect，则要注意在fxc命令中还要指定着色器的入口函数。fxc的具体用法参考SDK文档。
5，编辑Outputs为
               $(OutDir)/$(SafeInputName).fxo
6，编译项目，这时IDE会对Basic.fx进行编译，如同C++的编译一样，编译的结果也会在IDE的output窗口打印出来。

随便写写 2008-01-22 14:01 发表评论

Bump Mapping的实现

随便写写 — Mon, 31 Dec 2007 02:06:00 GMT

//vertex shader:

float3 fvLightPosition;
float3 fvEyePosition;
float4x4 matView;
float4x4 matViewProjection;

struct VS_INPUT
{
   float4 Position : POSITION0;
   float2 Texcoord : TEXCOORD0;
   float3 Normal :   NORMAL0;//通常只需要两个向量，因为另一个可以叉乘得到
   float3 Binormal : BINORMAL0;
   float3 Tangent : TANGENT0;

};

struct VS_OUTPUT
{
   float4 Position :        POSITION0;
   float2 Texcoord :        TEXCOORD0;
   float3 ViewDirection :   TEXCOORD1;
   float3 LightDirection:   TEXCOORD2;

};

VS_OUTPUT vs_main( VS_INPUT Input )
{
VS_OUTPUT Output;

   Output.Position         = mul( Input.Position, matViewProjection );
   Output.Texcoord         = Input.Texcoord;

   float3 fvObjectPosition = mul( Input.Position, matView );

   float3 fvViewDirection = fvEyePosition - fvObjectPosition;
   float3 fvLightDirection = fvLightPosition - fvObjectPosition;

   float3 fvNormal         = mul( Input.Normal, matView );
   float3 fvTangent        = mul( Input.Tangent, matView );
   float3 fvBinormal       = mul( Input.Binormal, matView );//通常输入只需要nornal和tangent，binormal可以由两者叉乘得到
   //fvBinormal = cross( fvNormal, fvTangent );

//将视方向和光线方向都转换到法线空间（或者称切线空间）
   Output.ViewDirection.x = dot( fvTangent, fvViewDirection );
   Output.ViewDirection.y = dot( fvBinormal, fvViewDirection );
   Output.ViewDirection.z = dot( fvNormal, fvViewDirection );

   Output.LightDirection.x = dot( fvTangent, fvLightDirection );
   Output.LightDirection.y = dot( fvBinormal, fvLightDirection );
   Output.LightDirection.z = dot( fvNormal, fvLightDirection );

   return( Output );

}

//Pixel Shader

float4 fvAmbient;
float4 fvSpecular;
float4 fvDiffuse;
float fSpecularPower;

sampler2D baseMap;
sampler2D bumpMap;

struct PS_INPUT
{
   float2 Texcoord :        TEXCOORD0;
   float3 ViewDirection :   TEXCOORD1;
   float3 LightDirection:   TEXCOORD2;

};

float4 ps_main( PS_INPUT Input ) : COLOR0
{
   float3 fvLightDirection = normalize( Input.LightDirection );
   float3 fvNormal         = normalize( ( tex2D( bumpMap, Input.Texcoord ).xyz * 2.0f ) - 1.0f );
   float fNDotL           = dot( fvNormal, fvLightDirection );

   float3 fvReflection     = normalize( ( ( 2.0f * fvNormal ) * ( fNDotL ) ) - fvLightDirection );
   float3 fvViewDirection = normalize( Input.ViewDirection );
   float fRDotV           = max( 0.0f, dot( fvReflection, fvViewDirection ) );

   float4 fvBaseColor      = tex2D( baseMap, Input.Texcoord );

   float4 fvTotalAmbient   = fvAmbient * fvBaseColor;
   float4 fvTotalDiffuse   = fvDiffuse * fNDotL * fvBaseColor;
   float4 fvTotalSpecular = fvSpecular * pow( fRDotV, fSpecularPower );

   return( saturate( fvTotalAmbient + fvTotalDiffuse + fvTotalSpecular ) );

}

随便写写 2007-12-31 10:06 发表评论

副法线和正切是什么?

随便写写 — Mon, 11 Jun 2007 08:09:00 GMT

法线，切线和副法线构成了所谓的切线空间（tangnet space），在Bump Mapping中，法线纹理中存储的法线值就是在切线空间内的。

从网上找了一段求切线和副法线的代码.
根据三个顶点的位置坐标和纹理坐标求面的副法线和正切

1//let P = v1 - v0
2D3DXVECTOR3 P = v1.pos - v0.pos;
3//let Q = v2 - v0
4D3DXVECTOR3 Q = v2.pos - v0.pos;
5float s1 = v1.s - v0.s;
6float t1 = v1.t - v0.t;
7float s2 = v2.s - v0.s;
8float t2 = v2.t - v0.t;
9
10//we need to solve the equation
11// P = s1*T + t1*B
12// Q = s2*T + t2*B
13// for T and B
14
15
16//this is a linear system with six unknowns and six equatinos, for TxTyTz BxByBz
17//[px,py,pz] = [s1,t1] * [Tx,Ty,Tz]
18// qx,qy,qz     s2,t2     Bx,By,Bz
19
20//multiplying both sides by the inverse of the s,t matrix gives
21//[Tx,Ty,Tz] = 1/(s1t2-s2t1) *  [t2,-t1] * [px,py,pz]
22// Bx,By,Bz                      -s2,s1     qx,qy,qz
23
24//solve this for the unormalized T and B to get from tangent to object space
25
26
27float tmp = 0.0f;
28if(fabsf(s1*t2 - s2*t1) <= 0.0001f)
29{
30    tmp = 1.0f;
31}
32else
33{
34    tmp = 1.0f/(s1*t2 - s2*t1 );
35}
36
37tangent.x = (t2*P.x - t1*Q.x);
38tangent.y = (t2*P.y - t1*Q.y);
39tangent.z  = (t2*P.z - t1*Q.z);
40
41tangent = tmp * tangent;
42
43binormal.x = (s1*Q.x - s2*P.x);
44binormal.y = (s1*Q.y - s2*P.y);
45binormal.z = (s1*Q.z - s2*P.z);
46
47binormal = tmp * binormal;

根据Maya里面的资料写了一个求取tangent的函数，输入为3个顶点的位置，法线和纹理坐标，输出是切线值，副法线可以由切线和法线叉乘得到。

inline bool floatEqual(float a, float b)
{
    return abs(a-b) < 0.00001f;
}

HRESULT ComputerTangent(D3DXVECTOR3 position[3], D3DXVECTOR3 normal[3], D3DXVECTOR2 texcoord[3],D3DXVECTOR3 oTangent[3])
{
    D3DXVECTOR3 edge1;
    D3DXVECTOR3 edge2;
    D3DXVECTOR3 crossP;

     //==============================================
    // x, s, t
    // S & T vectors get used several times in this vector,
    // but are only computed once.
    //==============================================
    edge1.x = position[1].x - position[0].x;
    edge1.y = texcoord[1].x - texcoord[0].x;// s-vector - don't need to compute this multiple times
    edge1.z = texcoord[1].y - texcoord[0].y;// t-vector

    edge2.x = position[2].x - position[0].x;
    edge2.y = texcoord[2].x - texcoord[0].x;// another s-vector
    edge2.z = texcoord[2].y - texcoord[0].y;// another t-vector

    D3DXVec3Cross(&crossP,&edge1,&edge2);
    D3DXVec3Normalize(&crossP,&crossP);

    bool degnerateUVTangentPlane = floatEqual(crossP.x, 0.0f);
    if(degnerateUVTangentPlane)
        crossP.x = 1.0f;

    float tanX = -crossP.y / crossP.x;

    oTangent[0].x = tanX;
    oTangent[1].x = tanX;
    oTangent[2].x = tanX;

    //--------------------------------------------------------
    // y, s, t
    //--------------------------------------------------------
    edge1.x = position[1].y - position[0].y;

    edge2.x = position[2].y - position[0].y;
    edge2.y = texcoord[2].x - texcoord[0].x;// another s-vector
    edge2.z = texcoord[2].y - texcoord[0].y;// another t-vector

    D3DXVec3Cross(&crossP,&edge1,&edge2);
    D3DXVec3Normalize(&crossP,&crossP);

    degnerateUVTangentPlane = floatEqual(crossP.x, 0.0f);
    if(degnerateUVTangentPlane)
        crossP.x = 1.0f;

    float tanY = -crossP.y / crossP.x;

    oTangent[0].y = tanY;
    oTangent[1].y = tanY;
    oTangent[2].y = tanY;

     //------------------------------------------------------
    // z, s, t
    //------------------------------------------------------
    edge1.x = position[1].z - position[0].z;

    edge2.x = position[2].z - position[0].z;
    edge2.y = texcoord[2].x - texcoord[0].x;// another s-vector
    edge2.z = texcoord[2].y - texcoord[0].y;// another t-vector

    D3DXVec3Cross(&crossP,&edge1,&edge2);
    D3DXVec3Normalize(&crossP,&crossP);

    degnerateUVTangentPlane = floatEqual(crossP.x, 0.0f);
    if(degnerateUVTangentPlane)
        crossP.x = 1.0f;

    float tanZ = -crossP.y / crossP.x;

    oTangent[0].z = tanZ;
    oTangent[1].z = tanZ;
    oTangent[2].z = tanZ;

    //------------------------------------------------------
    for( int i = 0; i < 3; i++)
    {
        // Ortho-normalize to normal
        float dot = D3DXVec3Dot(&oTangent[i],&normal[i]);
        oTangent[i] -= normal[i] * dot;

        // Normalize tangents
        D3DXVec3Normalize(&oTangent[i],&oTangent[i]);
    }

    return S_OK;
}

随便写写 2007-06-11 16:09 发表评论