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 Benchmarking Platform
Phoromatic Test Orchestration

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 News
  1. Fedora 22 Is Being Released Next Tuesday
  2. OpenWRT 15.05 Preparing Improved Security & Better Networking
  3. Using The New LLVM/Clang OpenMP Support
  4. Zapcc Claims To Be A "Much Faster C++ Compiler"
  5. Godot 1.1 Engine Release Brings New 2D Engine
  6. Intel VA-API Driver 1.6 Is Coming
  7. Canonical Is Reportedly Considering An IPO
  8. GNOME 3.18 - GTK3 Now Supports RandR 1.5
  9. Fedora 22 Risks Being Delayed Beyond Next Week
  10. Systemd 220 Has Finally Been Released
  11. LibreOffice 5.0 Beta 1 Released
  12. Allwinner Publishes New CedarX Open-Source Code
Latest Articles & Reviews
  1. Btrfs RAID 0/1 Benchmarks On The Linux 4.1 Kernel
  2. The State Of Various Firefox Features
  3. Intel Iris Graphics Performance With Mesa 10.6
  4. Fedora Workstation 22 Is Looking Great, Running Fantastic
Most Viewed News This Week
  1. The Linux 4.0 Kernel Currently Has An EXT4 Corruption Issue
  2. AMDGPU Open-Source Driver Code Continues Maturing
  3. Oculus Rift Suspends Linux Development To Focus On Windows
  4. Microsoft Open-Sources The Windows Communication Foundation
  5. LibreOffice 5.0 Open-Source Office Suite Has Been Branched
  6. Another HTTPS Vulnerability Rattles The Internet
  7. Linux 4.1-rc4 Kernel Arrives A Day Late
  8. Wayland / Weston 1.8 Release Candidate Arrives