Angus Dorbie (dorbie++at++sgi.com)
Thu, 30 Sep 1999 11:24:52 -0700
Satheesh Ganapathi Subramanian wrote:
>
> Hi Performers,
>
> I would like to know if performer offers a similar feature like the Opengl
> Imaging Extension for Color Table, SGI_color_table.
>
> I'd like to map video as a texture, but before mapping it, I would like
> to scale/bias the image to suit some brightness/contrast requirements. I
> presume this can be done using the Color_table extension in Opengl. How
> can I possibly do it using performer.
>
> Will I be able to use the PFTEX_MAGFILTER_COLOR filter for pfTexture to
> control the brightness of the image?
Yes man pftexture lists the Performer tokens for these. Even it it
weren't supported (and it is) You can apply anything the hardware
supports in draw callbacks. A texture stores it's state when you modify
it after a bind so for this particular requirement you would have been
able to specify the required filter once after applying the texture and
forever after it will remain as modified. You won't need to, just make
the Performer calls.
>
> Also, I would like to know how color keying can be done on video textures
> using performer. I'm extracting video using DIVO and would like to do some
> color keying on the video before texturing it.
The texture lookup to alpha would do it (caveat, I've never tried this)
or perhaps a color matrix would be more usefull but the GE's apply that
on the download. You can also apply a filter to the download if you want
a pre interpolated lookup. You might also want to consider applying a
more sophisticated algorithm on the host using CPU's and then
downloading the image.
Cheers,Angus.
--
"One of the best-known folk theorems of software engineering is that
60% to 75% of conventional software projects are either never
completed or rejected by their intended users. If that range is
anywhere near true (and I've never met a manager of any experience
who disputes it) then more projects than not are being aimed at goals
which are either (a) not realistically attainable, or (b) just plain
wrong."
Eric S. Raymond - The Cathedral and The Bazaar
For advanced 3D graphics Performer + OpenGL based examples and tutors:
http://www.dorbie.com/
This archive was generated by hypermail 2.0b2 on Thu Sep 30 1999 - 11:25:04 PDT