Ptex and OpenGL?

[geleto]

Are there any plans to have some GPU-related functionality in ptex?
Like:
- Packing the subtextures in a rectangular texture
- Seamless filtering with a pixel shader
- Texture management - on-demand loading of the necessary mip-maps
from the ptex file/cache.

[brentb]

On Jan 17, 12:57 pm, geleto <gel...@gmail.com> wrote:
> Are there any plans to have some GPU-related functionality in ptex?

Ptex has really only been focused on software rendering, and we have
no plans to add GPU features. It's not completely clear how to do so,
at least without driver support, but I'd love to see what people come
up with.

> Like:
> - Packing the subtextures in a rectangular texture

We implemented packing for OpenGL display in our paint program. There
hasn't been any plan to add it to the ptex library though. It could
be done but it's probably done better outside of the main library as
I'm guessing it's somewhat application-specific. The algorithm we
implemented was fairly straightforward. There are probably more
efficient ones, but ours is a fairly simple packing case given that
all textures our powers-of-two. We don't use any padding between the
textures either. This seems fine for a paint system (we don't use
filtering when displaying the textures) but for other apps the
requirements may be different.

> - Seamless filtering with a pixel shader

This is trickier of course. To get an idea of what's possible, take a
look at Cem Yuksel's Mesh Colors (http://www.cemyuksel.com/research/
meshcolors/).

> - Texture management - on-demand loading of the necessary mip-maps
> from the ptex file/cache.

The library does this but on the CPU side. You would need another
piece of software in to manage a GPU texture budget.

[canjiang ren]

> We don't use any padding between the textures either.  This seems fine for a paint system (we don't use
filtering when displaying the textures) but for other apps the requirements may be different. 

hello, curiously, how to fix the seam problem without texture padding (putting texels along uv shell border) when applying texture to each face? 

thank you in advance. ,

在 2010年1月19日星期二 UTC+8下午11:53:03，brentb写道：

[Brent Burley]

On Mon, Jul 13, 2015 at 8:10 PM, canjiang ren <renca...@gmail.com> wrote:

> We don't use any padding between the textures either.  This seems fine for a paint system (we don't use
filtering when displaying the textures) but for other apps the requirements may be different. 

hello, curiously, how to fix the seam problem without texture padding (putting texels along uv shell border) when applying texture to each face? 

thank you in advance. ,

In our paint system we disable filtering using GL_TEXTURE_MIN_FILTER=GL_NEAREST and GL_TEXTURE_MAG_FILTER=GL_NEAREST.  This results in point sampling which is noisy and aliased but has no seams.   Note: the artists prefer this to having filtered textures as it gives a better indication of the texture and we've used point sampling in our paint system since before we had Ptex for this reason; it was a bonus that we didn't have to solve the seam filtering issue for Ptex.