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. 13-Way Low-End GPU Comparison With AMD's AM1 Athlon
  2. ASUS AM1I-A: A Mini-ITX Board For Socketed Kabini APUs
  3. Mini-Box M350: A Simple, Affordable Mini-ITX Case
  4. Overclocking The AMD AM1 Athlon & Sempron APUs
Latest Linux Articles
  1. Ubuntu 12.04.4 vs. 13.10 vs. 14.04 LTS Desktop Benchmarks
  2. AMD OpenCL Performance With AM1 Kabini APUs
  3. A Quick Look At GCC 4.9 vs. LLVM Clang 3.5
  4. Are AMD Athlon/Sempron APUs Fast Enough For Steam On Linux?
Latest Linux News
  1. Borderlands Is Being Considered For Linux
  2. Mesa 10.0 & 10.1 Stable Get Updated
  3. Getting Hit By The Variable Performance Of The Public Cloud
  4. Git 2.0 Test Releases Begin With Many Changes
  5. Wine 1.7.17 Works On Its Task Scheduler, C Run-Time
  6. The Improv ARM Board Still Isn't Shipping; Riding A Dead Horse?
  7. Debian To Maintain 6.0 Squeeze As An LTS Release
  8. Wasteland 2 Is Finally Released For Linux Gamers
  9. FreeBSD Advances For ARM, Bhyve, Clang
  10. Ubuntu 14.04 LTS "Trusty Tahr" Officially Released
  11. Ubuntu 12.04 LTS vs. 14.04 LTS Server Benchmarks
  12. QEMU 2.0 Released With ARM, x86 Enhancements
Latest Forum Discussions
  1. Suggestions about how to make a Radeon HD 7790 work decently?
  2. The GNOME Foundation Is Running Short On Money
  3. Updated and Optimized Ubuntu Free Graphics Drivers
  4. Radeon 8000M problematic on Linux?
  5. Linux Kernel Developers Fed Up With Ridiculous Bugs In Systemd
  6. After Jack Keane, RuseSoft will briing Ankh 3 to Linux through Desura
  7. Suspected PHP Proxy Issue
  8. Change installation destination from home directory