1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

An OpenGL Optimization Extension Merged Into Mesa

Mesa

Published on 06 October 2013 02:49 PM EDT
Written by Michael Larabel in Mesa
18 Comments

Yesterday Mesa received support for a new OpenGL extension and after that another useful OpenGL 4.2 extension was added to Mesa and implemented within the Intel OpenGL Linux driver. This latest extension can be used for a driver performance optimization.

The newest extension implemented in Mesa and more specifically the Intel DRI driver is ARB_conservative_depth. The ARB_conservative_depth extension has been implemented for Ivy Bridge "Gen7" hardware and newer. With time, the extension will be implemented by the Radeon and Nouveau Gallium3D drivers. There is also support for ARB_conservative_depth within the Softpipe driver.

OpenGL's ARB_conservative_depth extension allows games and applications to pass information to the OpenGL driver for implementing a performance optimization of an early depth test run before the fragment shader so the driver can skip the evaluation process if the fragment will be discarded due to being occluded.

The OpenGL.org registry lays out the extension in full.
There is a common optimization for hardware accelerated implementation of OpenGL which relies on an early depth test to be run before the fragment shader so that the shader evaluation can be skipped if the fragment ends up being discarded because it is occluded.

This optimization does not affect the final rendering, and is typically possible when the fragment does not change the depth programmatically. (i.e.: it does not write to the built-in gl_FragDepth output). There are, however a class of operations on the depth in the shader which could still be performed while allowing the early depth test to operate.

This extension allows the application to pass enough information to the GL implementation to activate such optimizations safely.
The ARB_conservative_depth extension is a requirement for OpenGL 4.2 compliance. This Git commit enabled the Intel i965 ARB_conservative_depth depth support for Gen7+ hardware.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. Even With Re-Clocking, Nouveau Remains Behind NVIDIA's Proprietary Linux Driver
  2. The Power Consumption & Efficiency Of Open-Source GPU Drivers
  3. AMD R600g/RadeonSI Performance On Linux 3.16 With Mesa 10.3-devel
  4. Intel Pentium G3258 On Linux
Latest Linux Articles
  1. Nouveau vs. Radeon vs. Intel Tests On Linux 3.16, Mesa 10.3-devel
  2. KVM Benchmarks On Ubuntu 14.10
  3. X.Org Server 1.16 Officially Released With Terrific Features
  4. Ubuntu With Linux 3.16 Smashes OS X 10.9.4 On The MacBook Air
Latest Linux News
  1. Grand Theft Auto Running On Direct3D Natively On Linux Shows Gallium3D Potential
  2. GCC As A Just-In Time Compiler Is An Interesting Project
  3. Age Of Wonders III Is Still Being Ported To Linux
  4. Git 2.1 To Further Mainline Windows Support Patches
  5. Debian 8.0 Jessie Is Settling For Linux 3.16
  6. Meson: A Next-Gen Build System Showing Promise
  7. Linux 3.16-rc7 Calms Things Down For The Linux 3.16 Kernel
  8. Open-Source AMD Users Report Hawaii GPU Acceleration Is Working
  9. Linus Torvalds On GCC 4.9: Pure & Utter Crap
  10. Cauldron 2014: GCC & LLVM Will Look To Collaborate More
Latest Forum Discussions
  1. Linus Torvalds On GCC 4.9: Pure & Utter Crap
  2. Updated and Optimized Ubuntu Free Graphics Drivers
  3. Porting Mesa to the Playstation 2
  4. ASRock AM1H-ITX: One Of The Best AM1 Mini-ITX Motherboards
  5. Debian + radeonsi
  6. Open-source drivers on ATI R7 260X
  7. Table test
  8. How To Setup Radeon DPM On Ubuntu Linux