On Fri, Nov 11, 2011 at 08:53:13AM -0800, Eric Anholt wrote:
> On Thu, 3 Nov 2011 10:16:06 +0800, Yuanhan Liu <yuanhan....@linux.intel.com>
> wrote:
> > On Wed, Nov 02, 2011 at 02:18:46PM -0700, Eric Anholt wrote:
> > > On Wed, 2 Nov 2011 11:12:07 +0800, Yuanhan Liu
> > > <yuanhan....@linux.intel.com> wrote:
> > > > On Tue, Nov 01, 2011 at 05:57:36PM +0800, Yuanhan Liu wrote:
> > > > > According to bspec, MIPCnt(was set to intelObj->_MaxLevel) was used
> > > > > for
> > > > > min/mag filter mode determination. For a normal case with no mipmap
> > > > > like
> > > > > this:
> > > > >
> > > > > glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
> > > > > glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
> > > > >
> > > > > hardware would always choose mag filter(GL_LINEAR) here since MIPCnt
> > > > > was
> > > > > set to 0 zero, then would make LOD be zero. Then according the
> > > > > formula:
> > > > > MagMode = (LOD - Base <= 0)
> > > >
> > > > Here are some more comments about this: LOD is a pre-computed value. if
> > > > preClamp is enabled, then LOD would be:
> > > > LOD = min(min(MIPCnt, MAX_LOD), LOD);
> > > >
> > > > So, if MIPCnt was set to 0, and preClamp was enabled, then the _final_
> > > > LOD would be 0, and hardware choose mag filter.
> > > >
> > > > Thoughts?
> > >
> > > It took me a long time to understand what you were trying to fix here.
> >
> > Sorry for that :(
> >
> > > The story I've worked out is:
> > >
> > > "We can't optimize out uploading the other mipmap levels for
> > > non-mipmapped filtering modes if the min filter is not the same as the
> > > mag filter. This is because the min/mag decision is based on the
> > > computed LOD of the sample, and if we clamp the LOD to BaseLevel by not
> > > including the other levels, it will always choose the mag filter even if
> > > minification should have occurred.
> >
> > Yes.
> >
> > > See page FINISHME: citation of PRM."
> >
> > Sorry, what does this mean?
>
> If you're going to make a reference to the spec, if possible please
> quote the exact section from the public PRM, so the next person to find
> it has a nice reference to read up on.
>
> > Yeah, I saw that. While thinking about this issue, I thought another
> > patch to fix this issue. It's somehow against with the Bspec: preclamp
> > should be enabled for OpenGL driver.
> >
> > Anyway, here is the patch, and I'd like to know what's your thoughts.
>
> I think I liked the previous one more. While I couldn't come up with a
> testcase for how this one would break,
Here I attached a simple test case I wrote. The result is somehow
obvious: run it with i965 driver, you will find it use MAG
filter(linear), and run it with swrast driver, you will find it use MIN
filter(nearest, and that's what we want).
> I still think just disabling the
> minor optimization in this weird case is more obviously correct than
> this change.
It's OK to me.
Thanks,
Yuanhan Liu
#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define WIN_WIDTH 100
#define WIN_HEIGHT 100
#define TEX_WIDTH 256
#define TEX_HEIGHT 256
void Initial(void)
{
glClearColor(0.0,0.0,0.0,1.0);
}
static GLfloat * make_tex_data(void)
{
int i, j;
int index;
float color_table[][4] = {
0, 0, 0, 1,
1, 1, 1, 1,
};
float *tex_data = malloc(TEX_WIDTH * TEX_HEIGHT * 4 * sizeof(GLfloat));
float *p = tex_data;
for (i = 0; i < TEX_HEIGHT; i++) {
index = i % 2;
for (j = 0; j < TEX_WIDTH; j++) {
p[0] = color_table[index][0];
p[1] = color_table[index][1];
p[2] = color_table[index][2];
p[3] = color_table[index][3];
p += 4;
index = !index;
}
}
if (0) {
glDrawPixels(TEX_WIDTH, TEX_HEIGHT, GL_RGBA, GL_FLOAT,
tex_data);
glutSwapBuffers();
sleep(3);
}
return tex_data;
}
void myDisplay(void)
{
/* Texture stuff */
GLfloat *tex_data = make_tex_data();
glEnable(GL_TEXTURE_2D);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, TEX_WIDTH, TEX_HEIGHT, 0,
GL_RGBA, GL_FLOAT, tex_data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f);
glVertex2f(-1, -1);
glTexCoord2f(1.0f, 0.0f);
glVertex2f(1, -1);
glTexCoord2f(1.0f, 1.0f);
glVertex2f(1, 1);
glTexCoord2f(0.0f, 1.0f);
glVertex2f(-1, 1);
glEnd();
glutSwapBuffers();
}
int main(int argc,char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);
glutInitWindowSize(WIN_WIDTH, WIN_HEIGHT);
glutCreateWindow("tex-near-min");
glutDisplayFunc(myDisplay);
Initial();
glutMainLoop();
return 0;
}
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
