3 replies to this topic

[David Gallagher]

Hi, I've just tried implementing the box blur compute shader example and have found that the blur produces a dark border around the edges of the viewport.
the border increases with the size of the blur. Does anyone know how to remove this or is there something simple I have overlooked. thanks for any advice on this.
(I'm using dx11)

pic showing the issue...

[Reedbeta]

The filter kernel is going off the edge of the image. I'm guessing you're using the Load method in the shader; if so, you'll have to implement texel clamping yourself. It doesn't give you any built-in support for that, just returns black if you go off the edge.

If you're using the Sample method, on the other hand, you just need to set a sampler state that has the proper addressing mode, probably CLAMP.

[David Gallagher]

ah that makes sense, thanks Reedbeta, yes I'm using the load method and that would explain things, man there is always a gotcha waiting to jump out of the woodwork .

[David Gallagher]

Just thought i'd post this for anyone using Load method in hlsl and need to clamp the texture for things like box blur...

int2 ClampUV(uint x,uint y)
{
    //-------------------------------------------------------------
    return clamp(int2(x,y),int2(0,0),int2(imageW-1,imageH-1));
    //-------------------------------------------------------------
}