Search found 12 matches

by John Nagle
Mon Jun 17, 2013 5:40 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Is this 3D GJK intersection test code correct?
Replies: 1
Views: 4067

Re: Is this 3D GJK intersection test code correct?

The termination condition looks questionable. Termination for GJK is hard to get right. Back in the 1990s, Steven Cameron at Oxford and I struggled with this. See his web site for the code. It's possible to get into states where the solver is moving through a sequence of adjacent supports. Are you e...
by John Nagle
Mon Jun 17, 2013 5:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Bullet Physics FAQ, TODO List and Issue Tracker
Replies: 4
Views: 40856

Broken link

Erwin Coumans wrote:Bullet Frequently Asked Questions (FAQ)
http://www.continuousphysics.com/Bullet_Faq.pdf
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by John Nagle
Wed Jul 26, 2006 4:52 am
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Do Blender skeletons work with physics yet?
Replies: 1
Views: 3456

Do Blender skeletons work with physics yet?

Do skeletons and joints work right with physics yet?

If so, how do you apply a joint torque?

Thanks.
by John Nagle
Wed Jul 19, 2006 5:54 pm
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Blender 2.42 release physics bug report
Replies: 10
Views: 9524

- Is moment of inertia properly calculated for convex polyhedra? It is approximated, convex polyhedra, cylinders and cones are currently using an approximation of the local bounding box for inertia. Ah, that's why the spinning top looks kind of wierd. You know about this, right? Free code for momen...
by John Nagle
Wed Jul 19, 2006 1:42 am
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Blender 2.42 release physics bug report
Replies: 10
Views: 9524

Further question: How do you make a union of two convex objects without them having collision problems with each other? I tried making them a group, and that didn't work,and I tried making one a parent of the other, which didn't work either. Does that work yet?
by John Nagle
Tue Jul 18, 2006 10:49 pm
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Blender 2.42 release physics bug report
Replies: 10
Views: 9524

The spinning top test is working nicely. It's spinning, precessing, slowing down, falling down, rolling, reversing due to friction, and coming to a stop. I'm impressed. Few real-time physics engines get that right. Thanks. Some minor questions: - Where do you set coefficient of friction in the Blend...
by John Nagle
Mon Jul 17, 2006 7:13 am
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Blender 2.42 release physics bug report
Replies: 10
Views: 9524

The reference says that no object should be bigger than 50 units, so I reduced the big static convex to 45 x 45 x 1. With that, the objects stabilized properly. Now, on to the harder cases. (I understand you're trying to do this in single precision. Unless you really need to be on the PS2, don't do ...
by John Nagle
Sun Jul 16, 2006 6:15 am
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Blender 2.42 release physics bug report
Replies: 10
Views: 9524

No, it really doesn't work.

Hey John, Make sure that the right bounds are set to the objects. Press "n" in the 3d-window, once the big cube is selected, and make sure that scale is 1:1:1. You can apply the scale and rotation of an object by hitting ctrl+a OK, did that and fixed the scaling. Now the cone doesn't settle, it jus...
by John Nagle
Sat Jul 15, 2006 10:34 pm
Forum: Physics authoring tools, serialization, standards and related topics
Topic: Blender 2.42 release physics bug report
Replies: 10
Views: 9524

Blender 2.42 release physics bug report

Tried the following situation in Blender 2.42, release version: - Created a ground plane by stretching a cube. Marked it as an actor. Tilted the plane so that it was tilted about 25 degrees from horizontal. - Created a smaller cube, and a cone, above the ground plane. Marked both as Actor and Dynami...
by John Nagle
Fri Jun 30, 2006 5:01 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Microsoft simulation engine
Replies: 1
Views: 3344

Microsoft's physics engine

Microsoft is licensing the Novodex physics engine, as used by Ageia

The Microsoft robotics effort is actually quite small, and their system doesn't do much yet. Imagine Lego Mindstorms implemented via Microsoft Web Services using .NET and you'll have the picture.
by John Nagle
Tue Aug 16, 2005 7:50 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: The first ragdoll, from 1997
Replies: 0
Views: 3275

The first ragdoll, from 1997

Here, from 1997, is our Falling Bodies, probably the first system to do good rag-doll physics. All the hard cases work. Enjoy. http://www.animats.com/topics/videos.html This is a true spring-damper system, the first one that really worked right. It'snot an impulse-constraint system, so there's no "b...