Before attempting texture splatting, I used one texture streched over the terrain:
My first step was to export my alpha maps for each of my texures. I have 3 textures snow, dirt, and grass. That means to do splatting I would need 6 textures. Since Irrlicht only supports 4 textures I decided to merge my 3 apha map textures into a different color channel of one texture. See the example below:
With this approach I reduce my 6 texture requirement down to 4 textures. Plus it saves texture memory which is a good thing.
Since the fixed function pipeline doesn't support reading individual texture color channels, I had to write a pixel shader to make this work. Here is the code for the pixel shader:
Code: Select all
float4x4 matViewProjection : ViewProjection;
float texScale = 10.0;
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;
float2 alphamap : TEXCOORD0;
float2 tex : TEXCOORD1;
};
struct VS_OUTPUT
{
float4 Position : 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;
return( Output );
}
PS_OUTPUT ps_main(in VS_OUTPUT input)
{
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;
output.diffuse = n;
return output;
}
technique Default_DirectX_Effect
{
pass Pass_0
{
VertexShader = compile vs_2_0 vs_main();
PixelShader = compile ps_2_0 ps_main();
}
}
If anyone has any suggestions on how to improve this I'd love to hear it. Also, i'd really like to find out if there is way to by-pass the 4 texture limitation. I know you can reference texture paths in the pixel shader but this approach doesn't seem to work with Irrlicht. I'm currently at my 4 texture limit, so what options do i have if i wanted to incorporate a lightmap?
