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<channel>
	<title>Game Physics</title>
	<link>http://www.gphysics.com</link>
	<description>Erin's Physics Weblog</description>
	<pubDate>Sun, 24 Feb 2008 06:02:52 +0000</pubDate>
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			<item>
		<title>GDC 2008</title>
		<link>http://www.gphysics.com/archives/37</link>
		<comments>http://www.gphysics.com/archives/37#comments</comments>
		<pubDate>Sun, 24 Feb 2008 06:02:52 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/37</guid>
		<description><![CDATA[I once again participated in a physics tutorial at the GDC with the Essential Math crew.
You can download my slides here.
Just in case you missed it, Crayon Physics Deluxe won the IGF. Congratulations to Petri!
]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/37/feed</wfw:commentRss>
		</item>
		<item>
		<title>Position Correction</title>
		<link>http://www.gphysics.com/archives/35</link>
		<comments>http://www.gphysics.com/archives/35#comments</comments>
		<pubDate>Sat, 03 Nov 2007 06:10:14 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/35</guid>
		<description><![CDATA[I tried the several algorithms for position correction of Box2D&#8217;s revolute joint.
I looked at these systems:

simple pendulum (1m diameter sphere on a massless 5m stick) with an initial angular velocity of 100 rad/s.
suspension bridge with 30 1m long planks.
multi-link chain with 30 1m long links.

Here are the algorithms:
Baumgarte - A fraction of the position error [...]]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/35/feed</wfw:commentRss>
		</item>
		<item>
		<title>Buoyancy</title>
		<link>http://www.gphysics.com/archives/34</link>
		<comments>http://www.gphysics.com/archives/34#comments</comments>
		<pubDate>Wed, 10 Oct 2007 05:33:40 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/34</guid>
		<description><![CDATA[I wrote a chapter in Game Programming Gems 6 about the buoyancy algorithm I used in Tomb Raider. The algorithm is suited for polyhedra on flat water surfaces. I posted the code on the downloads page.
]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/34/feed</wfw:commentRss>
		</item>
		<item>
		<title>Box2D Lives!</title>
		<link>http://www.gphysics.com/archives/33</link>
		<comments>http://www.gphysics.com/archives/33#comments</comments>
		<pubDate>Tue, 11 Sep 2007 06:52:55 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/33</guid>
		<description><![CDATA[Box2D now has it own web site at box2d.org. The source is now hosted on SF and there are many new features and enhancements. There is even a forum at the new site! How modern.
I plan to continue supporting Box2D as I am addicted to physics programming. Please, somebody help me! 
]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/33/feed</wfw:commentRss>
		</item>
		<item>
		<title>G++ Update and Games</title>
		<link>http://www.gphysics.com/archives/31</link>
		<comments>http://www.gphysics.com/archives/31#comments</comments>
		<pubDate>Wed, 04 Jul 2007 04:41:06 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/31</guid>
		<description><![CDATA[I updated Box2D to support G++ and Linux. Please get it here and let me know if it compiles on Linux. This version is based on the GDC &#8216;07 version.
The fine folks over at Kloonigames have found Box2D useful and made a couple games with it. To mark the occasion, I have created a games [...]]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/31/feed</wfw:commentRss>
		</item>
		<item>
		<title>GDC 2007</title>
		<link>http://www.gphysics.com/archives/29</link>
		<comments>http://www.gphysics.com/archives/29#comments</comments>
		<pubDate>Sun, 11 Mar 2007 01:18:55 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/29</guid>
		<description><![CDATA[Hello all!
I again participated at the GDC, giving a physics tutorial with Jim Van Verth, Christer Ericson, Squirrel Eiserloh, Gino van den Bergen, and Marq Singer. I changed my presentation a bit this year because I wanted to coordinate better with the other speakers and I wanted to discuss Jacobians and more constraint types. I [...]]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/29/feed</wfw:commentRss>
		</item>
		<item>
		<title>Sequential Impulses</title>
		<link>http://www.gphysics.com/archives/28</link>
		<comments>http://www.gphysics.com/archives/28#comments</comments>
		<pubDate>Sun, 11 Mar 2007 01:10:43 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/28</guid>
		<description><![CDATA[In 2005 I had a poster session at the GDC called &#8220;Iterative Dynamics with Temporal Coherence.&#8221; Obviously, such an obscure title is not likely to gain the headlines at the GDC. Further, trying to describe the PGS algorithm to game developers proved to be quite challenging. Nevertheless, a couple people out there managed to struggle [...]]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/28/feed</wfw:commentRss>
		</item>
		<item>
		<title>The gPhysics Engine</title>
		<link>http://www.gphysics.com/archives/26</link>
		<comments>http://www.gphysics.com/archives/26#comments</comments>
		<pubDate>Thu, 18 Jan 2007 06:57:33 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/26</guid>
		<description><![CDATA[Back in 1999 I wrote a physics engine using joint coordinates (Featherstone) and a direct LCP solver (Lemke). By no coincidence, the engine was called gPhysics.
The Lemke solver sucks. It is slow and has numerical problems. However, I am now again interested in joint coordinates. So I dusted off my old code and came across [...]]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/26/feed</wfw:commentRss>
		</item>
		<item>
		<title>Split Impulses and Post Projection</title>
		<link>http://www.gphysics.com/archives/25</link>
		<comments>http://www.gphysics.com/archives/25#comments</comments>
		<pubDate>Tue, 09 Jan 2007 06:50:34 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/25</guid>
		<description><![CDATA[I&#8217;ve been tinkering with Box2D.
The original version uses Baumgarte stabilization of position errors. The problem with Baumgarte is that it affects the momentum, leading to bouncy or spongy constraints. I&#8217;ve attempted to address that problem with Split Impulses and Post Projection
Split Impulses works by making a separate set of pseudo velocities and impulses that serve [...]]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/25/feed</wfw:commentRss>
		</item>
		<item>
		<title>New Look</title>
		<link>http://www.gphysics.com/archives/20</link>
		<comments>http://www.gphysics.com/archives/20#comments</comments>
		<pubDate>Sat, 02 Sep 2006 21:29:56 +0000</pubDate>
		<dc:creator>Erin Catto</dc:creator>
		
		<category><![CDATA[General]]></category>

		<guid isPermaLink="false">http://www.gphysics.com/archives/20</guid>
		<description><![CDATA[I upgraded the site software and I&#8217;m trying a new theme. I also installed some anti-spam software, so hopefully the comment areas will be less cluttered.
]]></description>
		<wfw:commentRss>http://www.gphysics.com/archives/20/feed</wfw:commentRss>
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