Ran Yakir (rany++at++rtset.co.il)
Fri, 30 May 1997 14:27:14 +0000
> > Another thought: OpenGL has a limit for the dimensions a texture can have.
I
> > don't know about Octane, but when we exceed the limit on out iR (2048) the
> > texture is just scaled down. Try to put a 'printf("Max texture size:%d\n",
> > glGet(GL_MAX_TEXTURE_SIZE));' somewhere where OpenGL commands are legal
(draw
> > callback or so).
>
> Say Hallelujah! When I do this, it comes back with 512. That certainly
seems
> like the problem.
>
> Now the question is, what sets that limit? Is this something I can change to
> 1024? And can anybody verify that this would cause filtering?
The maximal texture size is a function of the texture memory size and the
structure of texture memory. For example, on RE with RM4 you had 4 MB of
texture memory separated into two banks of 2MB each. A texture of 1024x1024
with 16 bits/texel occupies a whole bank. If you want mipmaps, than it scales
down to 512x1024 because adjacent mipmap levels have to reside in different
banks. So the limitation on texture size is imposed by the architecture of the
texture memory of a machine. This means that you can't change it for a specific
machine. What you can do is use several smaller textures to replace a large
one. On Impact you had a small utility called 'tpage' which calculates the
texture memory usage and limitations for a specific texture parameters. I think
the same program applies to OCTANE too.
Ran
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