纹理拼接后的Wrap寻址

http://blog.youkuaiyun.com/xoyojank/article/details/3212425

 

 

拼接后的纹理:

正常的草地(不进行WRAP寻址):

WRAP = 5时的情况:

MinFilter = Linear时的情况:

shader实现:

[cpp] view plain copy print ?

1. sampler2D atlasTexture;  
2. float4 texRect;   //(left, top, width, height) of uv   
3. float2 invSize;   //(1/width, 1/height)   
4. float4 uvRange;   //(left, top, right, bottom) of uv   
5. float4 ps_main( float2 tex : TEXCOORD0 ) : COLOR  
6. {  
7.    // convert original uv to atlas uv's unit   
8.    tex *= texRect.zw;  
9.      
10.    float2 uv = tex - texRect.xy;  
11.    // bring coordinates into normalized local texture coord [0..1]   
12.    uv *= invSize;  
13.    // if texture repeats then coords are > 1, use frc to bring    
14.    // these coords back into [0, 1) interval.   
15.    uv = frac(uv);  
16.    // transform coords back to texture atlas coords   
17.    uv = uv * texRect.zw + texRect.xy;  
18.    // clamp to inside texture (to avoid bi-linear filter pulling in foreign texels)   
19.    uv = clamp(uv, uvRange.xy, uvRange.zw);  
20.    // use the original coords for mip-map calculation   
21.    return tex2Dgrad(atlasTexture, uv, ddx(tex), ddy(tex));  
22. }  

sampler2D atlasTexture; float4 texRect; //(left, top, width, height) of uv float2 invSize; //(1/width, 1/height) float4 uvRange; //(left, top, right, bottom) of uv float4 ps_main( float2 tex : TEXCOORD0 ) : COLOR { // convert original uv to atlas uv's unit tex *= texRect.zw; float2 uv = tex - texRect.xy; // bring coordinates into normalized local texture coord [0..1] uv *= invSize; // if texture repeats then coords are > 1, use frc to bring // these coords back into [0, 1) interval. uv = frac(uv); // transform coords back to texture atlas coords uv = uv * texRect.zw + texRect.xy; // clamp to inside texture (to avoid bi-linear filter pulling in foreign texels) uv = clamp(uv, uvRange.xy, uvRange.zw); // use the original coords for mip-map calculation return tex2Dgrad(atlasTexture, uv, ddx(tex), ddy(tex)); } 

Reference:

ShaderX3 : Improved Batching via Texture Atlases