Hi

Im trying to get fog to work with my custom shader in irrlicht engine. So in c++ i have this

class MyShaderCallBack : public video::IShaderConstantSetCallBack
{
public:
        virtual void OnSetConstants(video::IMaterialRendererServices* services,
                        s32 userData)
        {
                video::IVideoDriver* driver = services->getVideoDriver();
                // set clip matrix
                core::matrix4 worldViewProj;
                worldViewProj = driver->getTransform(video::ETS_PROJECTION);
                worldViewProj *= driver->getTransform(video::ETS_VIEW);
                worldViewProj *= driver->getTransform(video::ETS_WORLD);
                if (UseHighLevelShaders)
                        services->setVertexShaderConstant("matViewProjection", worldViewProj.pointer(), 16);
                else
                        services->setVertexShaderConstant(worldViewProj.pointer(), 4, 4);

				//send camPos
				core::vector3df pos = device->getSceneManager()->getActiveCamera()->getAbsolutePosition();
 
				if (UseHighLevelShaders)
					services->setPixelShaderConstant("camPos", reinterpret_cast<f32*>(&pos), 3);
				else
					services->setPixelShaderConstant(reinterpret_cast<f32*>(&pos), 8, 1);

		}
};

This should send the position of the cam to the shader. In hlsl i have this at the top of the file

loat3 camPos : register( c0 );
 

And the pixelshader output function (in hlsl) looks like this

PS_OUTPUT ps_main(in VS_OUTPUT input) 
{ 
   float texScale = 1.0;  
   PS_OUTPUT output = (PS_OUTPUT)0; 


   vector a = tex2D(AlphaMap, input.alphamap); 
   vector i = tex2D(TextureOne, mul(input.tex, texScale));
   vector j = tex2D(TextureTwo, mul(input.tex, texScale)); 
   vector k = tex2D(TextureThree, mul(input.tex, texScale)); 


   float4 oneminusx = 1.0 - a.x; 
   float4 oneminusy = 1.0 - a.y; 
   float4 oneminusz = 1.0 - a.z; 


   vector l = a.x * i + oneminusx * i; 
   vector m = a.y * j + oneminusy * l; 
   vector n = a.z * k + oneminusz * m; 


   //how to make use of camPos to alter diffuse here?
   
   output.diffuse = n; 
   return output; 
} 
 

It does some splatting for me on the terrain. Now i want to use camPos to make linear fog from real color to some grey starting at 1000 and being full fog at 1300 (lets just say). So i have to modify output.diffuse right? But i dont know how to do that... Plz help in any way you can.

Thanks

Erik

i dont have access since im doing a custom shader for splatting.

thanks for the link but the interpolation coefficient itself (between 0 and 1) is trivial its the other stuff i dont know how to get (i understand the basics of what fog is, only not how to do it, code-wise). The diffuse is simply the color. If i set it to n*0.5 it gets darkened. If i set it to n*0.0 everything gets black.

1. how do i define the color in hlsl that i need for fog?

2. how do i get the distance between my camPos and the vertex? The code above is all that is in the output function so what is the vertex position?

3. once i have the distance, how do i larp original color with fog color?

Thanks again

Ive really tried a lot with this...

E

noone? Im stuck at this point and i really need fog for my terrain.

Ok thanks guys. I now have the code below. It finally works!

But i use a static Depth so everything gets the same amount of fog. My camPos is a float3. But how do i get distance between it and the current pixel (which i will use as 'Depth')? I guess old pythagoras in 3d is out friend but i cannot get the coords of the pixel.

Or is the xyz-coordinates not possible to get instead i should use the techique you mention above?

Thanks a lot.

Erik

PS_OUTPUT ps_main(in VS_OUTPUT input) 
{ 
   float texScale = 1.0; 	
   PS_OUTPUT output = (PS_OUTPUT)0; 

   vector a = tex2D(AlphaMap, input.alphamap); 
   vector i = tex2D(TextureOne, mul(input.tex, texScale));
   vector j = tex2D(TextureTwo, mul(input.tex, texScale)); 
   vector k = tex2D(TextureThree, mul(input.tex, texScale)); 
 
   float4 oneminusx = 1.0 - a.x; 
   float4 oneminusy = 1.0 - a.y; 
   float4 oneminusz = 1.0 - a.z; 

   vector l = a.x * i + oneminusx * i; 
   vector m = a.y * j + oneminusy * l; 
   vector n = a.z * k + oneminusz * m; 

   //how to get real Depth?
   
   float FogStart=500;
   float FogEnd=1000;
   float Depth=750;
   float4 FogColor = float4(0.5f, 0.5f, 0.5f, 1.0f);
  
   float factor = (FogEnd - Depth) / (FogEnd - FogStart);
   if(factor<0)
	  factor=0;
   if(factor>1)
	  factor=1;
   
      
   output.diffuse = n*factor+(1-factor)*FogColor; 
   return output;
   
} 

This:

if(factor<0)
     factor=0;
if(factor>1)
     factor=1;

could be written as:

factor = saturate( factor );

or

float factor = saturate( (FogEnd - Depth) / (FogEnd - FogStart) );

But how do i get distance between it and the current pixel (which i will use as 'Depth')?

You could for example transform your vertex in world space in vertex shader:

void VertexMain(...)
{
     ...
     OUT.WorldPos = mul( IN.Position, World );
}

then in pixel shader get the distance from camera:

void PixelMain(...)
{
    ...
    float depth = distance( camPos, IN.WorldPos );
    ...
}

Hi belfegor

I change so my vs_main looks like (adds just one line, the rest is there from the splatting code)

VS_OUTPUT vs_main( VS_INPUT Input ) 
{ 
   VS_OUTPUT Output; 
   Output.Position = mul( Input.Position, matViewProjection ); 
   Output.alphamap = Input.alphamap; 
   Output.tex = Input.tex; 
   Output.WorldPos = mul( Input.Position, World );

   return( Output ); 
} 

But this "breaks" the shader (terrain looses texture entirely, like if i write an syntax error). Do i need to register "World" or something? I backtrack and add WorldPos to my VS_INPUT. This works fine.

struct VS_INPUT 
{ 
   float4 Position : POSITION0; 
   float4 WorldPos : POSITION0; 
   float2 alphamap : TEXCOORD0; 
   float2 tex : TEXCOORD1; 
}; 
 

What doesnt work is when i try to add it to my VS_OUTPUT structure like so:

struct VS_OUTPUT 
{ 
   float4 Position : POSITION0; 
   float4 WorldPos : POSITION0; 
   float2 alphamap : TEXCOORD0; 
   float2 tex : TEXCOORD1; 
}; 
 

This is what breaks the shader. Why? Dont I need it here? so i can set it in my VS_MAIN?

Thanks for your help

Erik

Didn't use Irrlicht for years now. I don't see how could it break the code.

Do you do the same as for "matViewProjection"?

services->setVertexShaderConstant("matViewProjection", worldViewProj.pointer(), 16);
services->setVertexShaderConstant("World", world.pointer(), 16);

if that is correct syntax on Irrlicht side.

Could you post complete shader?

Can you see the debug output from shader? There should be logger in Irrlicht that gather shader error/warning messages.

I added the second line to shadercallback. The first line was already the same. (But i use worldViewProd. for the second line not world.)

class MyShaderCallBack : public video::IShaderConstantSetCallBack
{
public:
        virtual void OnSetConstants(video::IMaterialRendererServices* services,
                        s32 userData)
        {
                video::IVideoDriver* driver = services->getVideoDriver();
                // set clip matrix
                core::matrix4 worldViewProj;
                worldViewProj = driver->getTransform(video::ETS_PROJECTION);
                worldViewProj *= driver->getTransform(video::ETS_VIEW);
                worldViewProj *= driver->getTransform(video::ETS_WORLD);
if (UseHighLevelShaders){
                        services->setVertexShaderConstant("matViewProjection", worldViewProj.pointer(), 16);
services->setVertexShaderConstant("World", worldViewProj.pointer(), 16);
}
                else
                        services->setVertexShaderConstant(worldViewProj.pointer(), 4, 4);


//send camPos
core::vector3df pos = device->getSceneManager()->getActiveCamera()->getAbsolutePosition();


if (UseHighLevelShaders)
services->setPixelShaderConstant("camPos", reinterpret_cast<f32*>(&pos), 3);
else
services->setPixelShaderConstant(reinterpret_cast<f32*>(&pos), 8, 1);
}
};
 

The complete shader is below. Note, the three lines are commented out (now the shader "works" but with same fogdensity for all points). Uncommenting the declaration in struct VS_OUTPUT breaks the shader, and i dont know why...

Thanks again

Erik

float3 camPos : register( c0 );


float4x4 matViewProjection : ViewProjection; 


sampler AlphaMap = sampler_state 
{ 
   ADDRESSU = WRAP; 
   ADDRESSV = WRAP; 
   ADDRESSW = WRAP; 
}; 


sampler TextureOne = sampler_state 
{ 
   MipFilter = LINEAR; 
   MinFilter = LINEAR; 
   MagFilter = LINEAR; 
   ADDRESSU = WRAP; 
   ADDRESSV = WRAP; 
   ADDRESSW = WRAP; 
}; 


sampler TextureTwo = sampler_state 
{ 
   MipFilter = LINEAR; 
   MinFilter = LINEAR; 
   MagFilter = LINEAR; 
   ADDRESSU = WRAP; 
   ADDRESSV = WRAP; 
   ADDRESSW = WRAP; 
}; 


sampler TextureThree = sampler_state 
{ 
   MipFilter = LINEAR; 
   MinFilter = LINEAR; 
   MagFilter = LINEAR; 
   ADDRESSU = WRAP; 
   ADDRESSV = WRAP; 
   ADDRESSW = WRAP; 
}; 



struct VS_INPUT 
{ 
   float4 Position : POSITION0; 
   float4 WorldPos : POSITION0; 
   float2 alphamap : TEXCOORD0; 
   float2 tex : TEXCOORD1; 
}; 


struct VS_OUTPUT 
{ 
   float4 Position : POSITION0; 
   //float4 WorldPos : POSITION0; 
   float2 alphamap : TEXCOORD0; 
   float2 tex : TEXCOORD1; 
}; 


struct PS_OUTPUT 
{ 
   float4 diffuse : COLOR0; 
}; 


VS_OUTPUT vs_main( VS_INPUT Input ) 
{ 
   VS_OUTPUT Output; 
   Output.Position = mul( Input.Position, matViewProjection ); 
   Output.alphamap = Input.alphamap; 
   Output.tex = Input.tex; 
   //Output.WorldPos = mul( Input.Position, World );




   return( Output ); 
} 


PS_OUTPUT ps_main(in VS_OUTPUT input) 
{ 
   float texScale = 1.0;  
   PS_OUTPUT output = (PS_OUTPUT)0; 


   vector a = tex2D(AlphaMap, input.alphamap); 
   vector i = tex2D(TextureOne, mul(input.tex, texScale));
   vector j = tex2D(TextureTwo, mul(input.tex, texScale)); 
   vector k = tex2D(TextureThree, mul(input.tex, texScale)); 


   float4 oneminusx = 1.0 - a.x; 
   float4 oneminusy = 1.0 - a.y; 
   float4 oneminusz = 1.0 - a.z; 


   vector l = a.x * i + oneminusx * i; 
   vector m = a.y * j + oneminusy * l; 
   vector n = a.z * k + oneminusz * m; 


   //we want the real Depth here, not the static one
   
   float FogStart=500;
   float FogEnd=1000;
   float Depth=750;
   //float Depth = distance( camPos, input.WorldPos );
   float4 FogColor = float4(0.5f, 0.5f, 0.5f, 1.0f);
    
   
   
   //factor
   float factor = (FogEnd - Depth) / (FogEnd - FogStart);
   factor=saturate(factor);
   
      
   output.diffuse = n*factor+(1-factor)*FogColor; 
   return output;
   
} 


technique Default_DirectX_Effect 
{ 
   pass Pass_0 
   { 
      VertexShader = compile vs_2_0 vs_main(); 
      PixelShader = compile ps_2_0 ps_main(); 
   } 
}