[PD] [GEM-dev] gl stack underflow

[Matteo Sisti Sette]

Well it seems that:

- by avoiding texunit 0 and (probably unnecessarily) 1, I have actually 
resolved the weird interactions with [pix_snap]
- I still have stack underflows and overflows printed at each frame 
which I'll investigate but it's probably not causing any "visible" issue
- What was still driving me crazy is that I didn't know that I have to 
take into account that the texture size is actually the next power of 
two of the expected image size.

Since using [pix_texture] you don't have to worry about "padded" image 
size, AND since ALL glsl examples in Gem use 512x512 images, gently 
"avoiding" the problem, I naively thought that a MxN image used as a 
texture would simply have its M pixels spanning the [0,1] range in the x 
axis (and same for N on y).

Is there some "standard" way, some utility function or something, to 
deal with non-power-of-two size textures? or have I to explicitely write 
the calculations to get the correct coordinates? I think I can do that, 
but if I can have the machine do it for me I prefer that :)

Thanks
m.

chris clepper escribió:
> pix_snap is probably using texunit 0 which is the default for any 
> texturing call.  pix_snap actually uses a function called 
> glReadPixels(), and that might use texture units internally to grab the 
> frame and store it before read back to main memory. 
> 
> Also, you cannot use any value for the texunit pix_texture uses most 
> GPUs have at least 8 so texunits 0 to 7 are valid.  Lots of GPUs have 
> much more than 8 so you have to figure out where they end.
> 
> On Fri, Jan 1, 2010 at 1:38 PM, Matteo Sisti Sette 
> <matteosistisette at gmail.com <mailto:matteosistisette at gmail.com>> wrote:
> 
>     Thank you for pointing me to the examples, but it definitely seems
>     there is some kind of interaction with [pix_snap]: even if I force
>     [gemframebuffer] to use texunit 0 and my textures to use texunits
>     1,2,3 and 4, I still get under/overflows as soon as pix_snap takes a
>     snap, and my shader is using a snapped picture (which does not
>     correspond to any other texture) instead of the texture I expect it
>     to use.......
> 
>     Well I will try to post a simplified patch because this explanation
>     of mine is a mess, but it seems I have to figure out how to avoid
>     pixsnap to mess with textures. It does not accept a texunit message
>     (dunnow if it would make any sense)......
> 
>     cyrille henry escribió:
> 
> 
> 
>         Matteo Sisti Sette a écrit :
> 
>             cyrille henry escribió:
> 
>                 there is an exemple of how to use multiple texture /
>                 textunit in the gem exemple folder, in directory 10.GLSL
> 
> 
> 
>             You mean 05.multitexture.pd?
> 
>             Yes I've seen it (it is thanks to that example that I have
>             been able to do something - btw iirc it is yours, so thank you).
> 
>             But that doesn't show any interaction with [gemframebuffer]
>             nor [pix_snap]. That's where my troubles begin (apparently)
> 
>         the exemple 06 show how to use gemframebuffer and multiple texture.
> 
>         exemple 07 is also usefull for you.
> 
>         c
> 
> 
> 
> 
>     -- 
>     Matteo Sisti Sette
>     matteosistisette at gmail.com <mailto:matteosistisette at gmail.com>
>     http://www.matteosistisette.com
> 
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-- 
Matteo Sisti Sette
matteosistisette at gmail.com
http://www.matteosistisette.com