i965: Using EWA algorithm for isotropic case
Submitted by pav..@..el.com
Assigned to Ian Romanick
Description
Tests "MesaDemos tests/texfilt" and Test "MesaDemos tests/mipmap_tunnel" started to show an expected results (the transition from one mipmap level to another should be nice and regular/circular) for anisotropic case (2x - 16x) after EWA algorithm was enabled in Mesa: http://cgit.freedesktop.org/mesa/mesa/commit/?id=f74cf5f80ea6ea16abb38c28c2b4826b8559017b
But for isotropic case (1x) something like a polar rose is still observed. The screenshots are attached below. This is because EWA algorithm was enabled in Mesa only for anisotropic case.
But EWA algorithm also can be enabled for isotropic case. At least Haswell programming notes (Volume 2d: Command Reference: Structures(Haswell), Page 271) contains the following lines: "When EWA used for non-anisotropic filtering and the coordinates have zero derivative the computed LOD is 0 instead of -inf."
I enabled EWA algorithm for isotropic case too and expected results were observed for both tests. The screenshots are attached below.
Also I run these tests on Nvidia and observed that they also work as expected. The screenshots are attached below.
Could we use EWA for isotropic case? Or just say that this polar rose is ok for isotropic case and performance is more important for us here.
Version: 10.2