Re: [Mesa3d-dev] s_texture.c

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

Daniel Vogel wrote:
> 
> hi`
> 
> I tried running UT with the Mesa software renderer and when I turned on
> trilinear filtering it crashed in sample_2d_linear being called with a
> NULL pointer for the image from sample_2d_linear_mipmap_linear. The
> problem seems to be that UT uses GL_TEXTURE_MAX_LEVEL and tObj->_P was 7
> and tObj->_M was 5. From what I can read in mtypes.h shouldn't _M be
> used instead of _P in the following code? Changing the code to use _M at
> least made it work ;) BTW, why is _M a float and not an integer?
> 
> s_texture.c:840 [sample_2d_linear_mipmap_linear]
> 
> if (level >= tObj->_P) {
>    sample_2d_linear( tObj, tObj->Image[tObj->_P], s, t, rgba);
> }
> else {
>    GLchan t0[4], t1[4];  /* texels */
>    const GLfloat f = myFrac(lambda);
>    sample_2d_linear( tObj, tObj->Image[level  ], s, t, t0 );
>    sample_2d_linear( tObj, tObj->Image[level+1], s, t, t1 );
>    rgba[RCOMP] = (GLchan) (GLint) ((1.0F-f) * t0[RCOMP] + f * t1[RCOMP]);
>    rgba[GCOMP] = (GLchan) (GLint) ((1.0F-f) * t0[GCOMP] + f * t1[GCOMP]);
>    rgba[BCOMP] = (GLchan) (GLint) ((1.0F-f) * t0[BCOMP] + f * t1[BCOMP]);
>    rgba[ACOMP] = (GLchan) (GLint) ((1.0F-f) * t0[ACOMP] + f * t1[ACOMP]);
> }


Are you settting GL_TEXTURE_BASE_LEVEL?

I think I see an error in the calculation in _P.  I think I should
add the base level to it.  However, that would increase _P.

I'll have to review the spec and write a test program.  I do think
there is a bug here.  Thanks for flagging it.

-Brian