Re: [Mesa3d-dev] Possible bug in s_texture.c

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

Abaco wrote:
> 
> Hi,
> 
> I´m sitting here in an internet-shop in Spain, so if you won´t be able to
> mail me, for now. But monday I´m back in the Netherlands.
> 
> I think an error exists in the function _swrast_choose_texture_sample_func
> in the file src/swrast/s_texture.c.
> 
> Instead of
> 
>       if (needLambda) {
>          /* Compute min/mag filter threshold */
>          if (t->MagFilter==GL_LINEAR
>              && (t->MinFilter==GL_NEAREST_MIPMAP_NEAREST ||
>                  t->MinFilter==GL_LINEAR_MIPMAP_NEAREST)) {
>             swrast->_MinMagThresh[texUnit] = 0.5F;
>          }
> 
> it should be
> 
>       if (needLambda) {
>          /* Compute min/mag filter threshold */
>          if ((t->MagFilter==GL_LINEAR &&
>              t->MinFilter==GL_LINEAR_MIPMAP_NEAREST) ||
>              (t->MagFilter==GL_NEAREST &&
>                  t->MinFilter==GL_NEAREST_MIPMAP_NEAREST)) {
>             swrast->_MinMagThresh[texUnit] = 0.5F;
>          }

See section 3.8.6 of the 1.2 spec.  It says if the mag filter is
GL_LINEAR and (min filter is GL_NEAREST_MIPMAP_NEAREST or min filter
is GL_NEAREST_MIPMAP_LINEAR) then c = 0.5, else it's 0.

Note that Mesa is indeed wrong, but not in the way you point out.
I should replace GL_LINEAR_MIPMAP_NEAREST with GL_NEAREST_MIPMAP_LINEAR.

I'm wonder if that got changed from the 1.0 spec at one point.

-Brian