On Fri, 8 Jun 2012 14:31:16 -0600, Brian Paul <[email protected]> wrote: > diff --git a/tests/general/drawpix-z.c b/tests/general/drawpix-z.c > new file mode 100644 > index 0000000..cdd6ac9 > --- /dev/null > +++ b/tests/general/drawpix-z.c
The code would have made more sense to me if you had:
float ndc(float z)
{
return -1.0 + 2.0 * z;
}
> +static void
> +draw_z_gradient(GLfloat zLeft, GLfloat zRight)
> +{
> + GLfloat verts[4][3];
> +
> + verts[0][0] = -1.0; verts[0][1] = -1.0; verts[0][2] = zLeft;
> + verts[1][0] = 1.0; verts[1][1] = -1.0; verts[1][2] = zRight;
> + verts[2][0] = 1.0; verts[2][1] = 1.0; verts[2][2] = zRight;
> + verts[3][0] = -1.0; verts[3][1] = 1.0; verts[3][2] = zLeft;
verts[0][0] = -1.0; verts[0][1] = -1.0; verts[0][2] = ndc(zLeft);
verts[1][0] = 1.0; verts[1][1] = -1.0; verts[1][2] = ndc(zRight);
verts[2][0] = 1.0; verts[2][1] = 1.0; verts[2][2] = ndc(zRight);
verts[3][0] = -1.0; verts[3][1] = 1.0; verts[3][2] = ndc(zLeft);
> +enum piglit_result
> +piglit_display(void)
> +{
float left = epsilon;
float right = 1.0 - epsilon;
> +
> + /* create image of Z values increasing from left to right */
> + buf = (GLfloat *)
> + malloc(piglit_width * piglit_height * sizeof(GLfloat));
> + for (j = 0; j < piglit_height; j++) {
> + for (i = 0; i < piglit_width; i++) {
> + float z = i / (float) (piglit_width - 1);
> + z = epsilon + (z * (1.0 - 2.0 * epsilon));
z = left + i * (right - left);
> + buf[j * piglit_width + i] = z;
> + }
> + }
> +
> + /* draw a red quad behind the Z gradient - it should not be visible */
> + glColor4fv(red);
> + draw_z_gradient(-1.0 + 2.0 * epsilon, 1.0);
draw_z_gradient(left + epsilon, right + epsilon);
> + draw_z_gradient(-1.0, 1.0 - 2.0 * epsilon);
draw_z_gradient(left - epsilon, right - epsilon);
With the code you had, if I'm reading this right, the epsilon in
drawpixels is on a different scale from the epsilon in draw_z_gradient,
so on the +/- (1.0 - 2.0 * epsilon) side, the zs are equal to the
z that was DrawPixels()ed, and basically you're getting lucky.
I think it's an interesting test to have because of not exercising
readpixels, though.
pgplnPoUohMMY.pgp
Description: PGP signature
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