How to calculate view transform in shader code

akira32 · 发表于 2009-2-9 15:19:00

How to calculate view transform in shader code?
I have a special requirement to calculate the view tranformation in Exponential Fog. I want to implement the pixel fog into shader code, becuase the objects in my scene all are used effect file. So I cannot use SetRenderState to set the pixel fog.

I saw the Fog Formulas (Direct3D 9). This part describes as below:

For range based fog, the value for d is the distance between the camera position and a vertex.
For non-range based fog, the value for d is the absolute value of the Z-coordinate in camera space.

复制代码

I have a confusion in the word of "the absolute value of the Z-coordinate in camera space". How do I calculate the value in shader code if the camera always is at the skydorme's top? And 3ds max DierctX Shader material will show the result synchonizately.(If I can calculate the view matrix from skydrome'top in shader code)

There are my shader code to calculate the fog as below:

//vertex shader
v2f av(a2v In, uniform float3 lightPosition)
{
v2f Out = (v2f)0;
Out.position = mul(In.position, wvp); //transform vert position to homogeneous clip space
//this code was added by the IN UV Node
Out.texCoord = In.texCoord; //pass through texture coordinates from channel 1
//FOG_NONE
if (UIConst_FogType==0)
{
Out.fogLerpParam=0.0f;
}
else
{
float4 tmPos;
if (UIConst_FogType==1)//FOG_EXP1
{
tmPos=mul(In.position,world*view);
float dist;
#ifdef _3DSMAX_
dist=UIConst_FogRadius-tmPos.z;
#else
dist=UIConst_FogRadius-tmPos.y;
#endif
Out.fogLerpParam = 1/exp(dist*UIConst_FogDensity);
}
else if (UIConst_FogType==2)//FOG_EXP2
{
tmPos=mul(In.position,world*view);
float dist;
#ifdef _3DSMAX_
dist=UIConst_FogRadius-tmPos.z;
#else
dist=UIConst_FogRadius-tmPos.y;
#endif
Out.fogLerpParam = 1/exp(pow(dist*UIConst_FogDensity,2));
}
else if (UIConst_FogType==3)//FOG_LINEAR
{
tmPos=mul(In.position,world);
float gFogRange=UIConst_FogEnd-UIConst_FogStart;
float dist;
#ifdef _3DSMAX_
dist=UIConst_FogRadius-tmPos.z;
#else
dist=UIConst_FogRadius-tmPos.y;
#endif
Out.fogLerpParam = saturate((dist - UIConst_FogStart) / gFogRange);
}
}
return Out;
}
//pixel shader
float4 af(v2f In, uniform float4 lightColor) : COLOR
{ ......
float4 ret = float4(0,0,0,1);
ret = float4(input1, 1);
if (UIConst_FogType==0)
{
}
else
{
float3 final = lerp(ret.rgb , UIColor_FogColor, In.fogLerpParam);
ret=float4(final,1.0f);
}
return ret;
}

复制代码

PS:UIConst_XX is the UI widget showed in 3ds max's DirectX Shader material.

qrli · 发表于 2009-2-9 19:58:00

pass in the true view matrix through another uniform.

But seriously, you don't need to apply fog to the skydome.

akira32 · 发表于 2009-2-17 14:52:00

I had solved this problem by reference the book "ShaderX2 Introdutuion & Tutorials with DirectX 9"(Introduction to Different Fog Effects).

//vertex shader
v2f av(a2v In, uniform float3 lightPosition)
{
v2f Out = (v2f)0;
Out.position = mul(In.position, wvp); //transform vert position to homogeneous clip space
//this code was added by the IN UV Node
Out.texCoord = In.texCoord; //pass through texture coordinates from channel 1
//FOG_NONE
if (UIConst_FogType==0)
{
Out.fogLerpParam=0.0f;
}
else
{
float4 tmPos;
float dist;
float4 upW;
#ifdef _3DSMAX_
upW=float4(0.0f,0.0f,UIConst_FogRadius,1.0f);
#else
upW=float4(0.0f,UIConst_FogRadius,0.0f,1.0f);
#endif
tmPos=mul(In.position,world);
if (UIConst_FogType==1)//FOG_EXP1
{
dist=distance(upW,tmPos)/UIConst_FogEnd*4.0f;
Out.fogLerpParam = exp(-dist*UIConst_FogDensity);
}
else if (UIConst_FogType==2)//FOG_EXP2
{
dist=distance(upW,tmPos)/UIConst_FogEnd*4.0f;
Out.fogLerpParam = exp(-pow(dist*UIConst_FogDensity,2));
}
else if (UIConst_FogType==3)//FOG_LINEAR
{
float gFogRange=UIConst_FogEnd-UIConst_FogStart;
dist=distance(upW,tmPos);
Out.fogLerpParam = saturate((dist - UIConst_FogStart) / gFogRange);
}
}
return Out;
}
//pixel shader
float4 af(v2f In, uniform float4 lightColor) : COLOR
{ ......
float4 ret = float4(0,0,0,1);
ret = float4(input1, 1);
if (UIConst_FogType==0)
{
}
else
{
if (UIConst_FogType==1 || UIConst_FogType==2)
{
float3 final = lerp(UIColor_FogColor.rgb , ret.rgb, In.fogLerpParam);
ret=float4(final,1.0f);
}
else if (UIConst_FogType==3)
{
float3 final = lerp(ret.rgb , UIColor_FogColor.rgb, In.fogLerpParam);
ret=float4(final,1.0f);
}
//ret=float4(UIColor_FogColor.rgb,1.0f);
}
return ret;
}

复制代码

账号		自动登录	找回密码
密码			立即注册

How to calculate view transform in shader code

Re:How to calculate view transform in shader code

Re:How to calculate view transform in shader code