Re: [Mesa3d-dev] higher bit depth support

[Brian P. <br...@va...>]

Back in October, luc-eric rousseau wrote:
> 
> Hello,
> for research, I would like to modify Mesa to support 16 bit per channel
> texture, as well as a higher precision render buffers, either 16 bit or
> single-precision floating point.
> 
> The goal here is to use Mesa to render (non-interactivly) in software high
> precision 3D images made with 16 bit texture source, without loss of
> quality.  The current precision of the vertex coordinates is fine, it's the
> precision of the shading and the alpha blending that matters.  The rendered
> images are not meant for PC monitors (which are only 8 bit per channel max).
> 
> My question is: how much trouble would it be?  Of course, I've already
> looked at the source, but I would like to get an idea of how much of the
> code I would have to change, and if there are roadblocks I would hit.  I
> should also point out that i'm lazy :^)


Got some good news for you.  Mesa now has support for 16-bit color channels.
There's probably a number of bugs to fix yet but I ran some tests last night
and it seems to work.  I haven't exercised texturing yet so there could be
problems there.

If you want to play with it, here's what you have to do:

1. Get the latest Mesa CVS trunk code.

2. Edit src/config.h and change CHAN_BITS to 16.

3. Edit src/Makefile.X11 and remove DRIVER_SOURCES from the OBJECTS assignment.

4. make -f Makefile.X11 linux-debug  (this'll help if you find bugs)

5. Mesa/tests/osdemo16.c is a modified version of the osdemo.c program which
   renders a 16-bit/channel image and writes it as an 8-bit/channel targa
   file (dropping the least significant bits).  Only the OSMesa interface
   supports 16-bit channels at this time.

Let me know how it works if you try it.

-Brian