https://bugs.freedesktop.org/show_bug.cgi?id=36602
Summary: Hierarchical Z support for R600 Product: DRI Version: DRI CVS Platform: Other OS/Version: All Status: NEW Severity: enhancement Priority: medium Component: DRM/Radeon AssignedTo: dri-devel@lists.freedesktop.org ReportedBy: pelloux@gmail.com
Add Hierarchical Z (HiZ) support for r600g driver.
I'm attaching my work-in-progress patchs to this bug report to keep track of comments.
This patch adds 3 new env vars : - R600_EARLYZ : controls whether EarlyZ functionnality is used (DB_SHADER_CONTROL register) - R600_HIZ : HiZ enabled/disabled - R600_HIZ_READ_HACK : this one is a quick hack for debugging HiZ data buffer. If set, data will be read from HiZ bo instead of depth buffer bo when calling glReadPixels( ... GL_DEPTH_COMPONENT ...)
General notes on HiZ on r600 : (all testing done using : ATI Technologies Inc RV770 [Radeon HD 4850])
* HiZ buffer is made of DWORD entries. Each DWORD represents one tile (4x4 or 8x8 pixels depending DB_HTILE_SURFACE register fields) * HiZ buffer does not need to be manually cleared by the driver * DB_RENDER_CONTROL:RESUMMARIZE_ENABLE bit is not necessary to get it working - but if enabled it slows things down * application performance are roughly the same using R600_EARLYZ or R600_HIZ
Know problems : * Hierarchical Stencil has not been tested * HiZ buffer data layout is still unclear. As an example : using 640x640 window and 8x8 tiles. HiZ buffer should contain (640/8)*(640/8) = 6400 entries. When reading it back using the above hack, it contains 6400 entries but spread on the 7680 first dwords of the buffer. Therefore HiZ bo if largely oversized for now (ie = depth buffer size)