Re: [Algorithms] 2D in a 3D world

[Colin B. <bar...@gm...>]

Direct3D texel offset perchance?

http://msdn.microsoft.com/en-us/library/bb219690(VS.85).aspx

On 7 August 2010 22:20, Jason Hughes <jh...@st...> wrote:

> I've been trying to resolve an issue where full screen textures being
> drawn through the 3D system appear blurry.  I feel like I'm probably not
> considering something.  Any ideas would be welcome!
>
> - I'm using an orthographic projection matrix along Z, a view matrix
> that is pretty much identity except for some negations on various axes
> to correct for LH/RH differences in the engine.
> - The quad is mapped to the full screen both for vertex positions and
> UVs (0,0,1) to (1,1,1), since the ortho matrix is 0..1, not in screen
> pixels.
> - The texture has the exactly the same number of pixels in both
> directions as the back buffer.
> - Back buffer and window match resolution exactly.
> - Resolution is 1024x600 (but problem exists in other resolutions)
> - Texture sampling is bilinear or anisotropic (shouldn't matter).  Both
> show the problem.  Sometimes my 2D stuff needs to cleanly scale, so I
> can't force point sampling globally.  Texture matrix is disabled.
>
> Steps I've taken to debug:
> - I made a simple texture with regions that are alternating white and
> black columns and rows that are 1, 2, and 4 pixels wide, so I could see
> what was happening with texture sampling.  The result is an even gray in
> the 1-pixel wide areas, but can be made brighter and darker depending on
> the offset I put into the matrices.  Half-pixel adjustment didn't fix
> it.  I never get white or black lines.
> - I checked to make sure that the test image wasn't being munged by the
> texture processing tools and it's perfectly clean (no GIGO).
>
> I can understand not getting perfect rasterization vertically due to the
> height being a non-power-of-two, but I expected columns to be cleanly
> mapped.  What else should I be looking for?
>
> Most appreciated,
> JH
>
> Jason Hughes
> President
> Steel Penny Games
> Austin, TX
>
>
>
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