Weird screen space seam (pixel size) when implementing atlas shader (image inside)

Unity Engine
1

I’m writing a simple atlas shader aware texel bleeding between subtexture regions but I’m not getting that instead I’m getting a horrible seam in screen space the size of pixels.

I’ve tried different texture filter modes bilinear (left) and point (right); In the attached image you can also see that I’ve left some padding so I shouldn’t be getting region “bleeding”.

The shader looks like this:

per vertex
o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
o.posMS = abs(v.vertex.xyz);

per pixel
float2 fuv = frac(i.posMS.xz)*scale+offset;
float3 texColor = tex2D(_TextureAtlas, fuv).xyz;
return float4(texColor, 1);

1260449--55291--$pixelSeam.jpg
1260449--55291--$pixelSeam.jpg1931×1715 463 KB

Don’t have a clue of what could be happening. Thanks for any hint!

2

Found it. It’s important to disable mip-mapping for that texture by using the “advanced texture type”.

3

The other problem is that you’re using Frac. The texture might still work without it, as long as it’s set to repeat and not clamp.