Search found 231 matches
- Fri Oct 19, 2007 4:33 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Updating vertex positions
- Replies: 4
- Views: 5350
Re: Updating vertex positions
OK, I'm not a good person to answer questions about TOI and CCD, however I'll make a comment or two nonetheless: Correct me if I'm wrong, but Implicit Euler typically uses an estimate of the force at the next timestep to calculate the next velocity, and then that updated velocity is used to update t...
- Thu Oct 18, 2007 3:45 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Updating vertex positions
- Replies: 4
- Views: 5350
Re: Updating vertex positions
It depends on the type of integration used for the motion. What you are describing is part of what I've seen called the "parabolic" integrator. It's accurate when the forces are constant for the entire timestep. The problem is that it is fairly unstable when simulating springs and dampers ...
- Wed Oct 17, 2007 4:14 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Force Limited Velocity Constraints: what are they??
- Replies: 7
- Views: 9107
Re: Force Limited Velocity Constraints: what are they??
Thanks. Yeah, I understood it better after visiting http://en.wikipedia.org/wiki/PID_controller, and why the I or other letters can be dropped.
- Wed Oct 17, 2007 3:28 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Force Limited Velocity Constraints: what are they??
- Replies: 7
- Views: 9107
Re: Force Limited Velocity Constraints: what are they??
Just to clarify, what does P and D stand for? I thought PID means proportional-integral-derivative, but then you guys are also just saying PD sometimes. And then Erin says values of P and D ... sounds a bit like spring and damper but I'm not clear.
- Mon Oct 15, 2007 8:51 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Resting Contact in rigid body simulation. . .
- Replies: 38
- Views: 45429
Re: Resting Contact in rigid body simulation. . .
The constraints are solved pair-wise between two bodies, with no limit to the number of pairs. There may be some confusion - I'm perfectly aware of your statement. I'm talking about constraints between three or more bodies. Maintaining the area of a triangle in a particle system such as cloth can b...
- Mon Oct 15, 2007 4:02 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Resting Contact in rigid body simulation. . .
- Replies: 38
- Views: 45429
Re: Resting Contact in rigid body simulation. . .
It is funny, because one of the benefits of pair-wise applying impulses on rigidbodies (relaxation, Sequential Impulse) is very intuitive and easy to understand. So it would be good to explain this first in terms of bodies, velocities, impulses, instead of trying to explain it using the less intuit...
- Mon Oct 08, 2007 7:41 pm
- Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
- Topic: Is SIMD math worth the effort??
- Replies: 8
- Views: 19670
Re: Is SIMD math worth the effort??
I spent a couple weeks trying to improve the performance of my math library using SSE2. In the end, I simply gave up because the loads into the XMM registers took so long they usually killed any performance benefit. My 3-float vectors matched or beat aligned 4-float vectors in almost all cases (yes ...
- Wed Oct 03, 2007 6:06 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Intel buys Havok
- Replies: 28
- Views: 41733
Re: Intel buys Havok
I don't see where they claim it's useless. They're just concerned about language discrepancies, turnaround on bug, and lack of understanding on how their entire engine works. So they've concluded it would be better to develop it themselves.
Why not Bullet?
Why not Bullet?
- Tue Sep 25, 2007 2:01 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Intel buys Havok
- Replies: 28
- Views: 41733
Re: Intel buys Havok
1) Marketing and
2) an architecture that is not completely resistant to parallelization (which will indirectly lead to better Marketing).
2) an architecture that is not completely resistant to parallelization (which will indirectly lead to better Marketing).
- Fri Sep 21, 2007 3:12 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Intel buys Havok
- Replies: 28
- Views: 41733
Re: Intel buys Havok
So my question is how they make programming easier for such architecture, and how they deal with memory/cache/DMA for all those cores. In answer to the second part of your question, the paper basically admits as much in the introduction: "A radical re-design of the memory hierarchy may be nece...
- Fri Aug 24, 2007 5:10 pm
- Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
- Topic: Impulse-based dynamic simulation library (IBDS)
- Replies: 94
- Views: 128255
Of course the parabolic integrator can't be used for rotation integration. I use a Runge-Kutta of fourth order for this. Just FYI, there's probably a better method out there if you're looking to accurately integrate rotations including the gyroscopic (coriolis) effects: http://math.ucsd.edu/~sbuss/...
- Tue Aug 21, 2007 6:53 pm
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Multi-Level "Weight" Simulation
- Replies: 26
- Views: 29592
So the real question is the following: using _only_ the information locally available to a single contact, maybe including information from previous iterations, is there a way for the contact to figure out how to alter its response between two bodies so as to accelerate convergence when those bodes...
- Tue Aug 14, 2007 3:21 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Problem with btCompoundShape
- Replies: 7
- Views: 6525
Gravity pulls straight down on everything, it wouldn't change the orientation. What changes the orientation of a lawn dart is the wind resistance of the blades. The aerodynamics forces on the blades are behind the center-of-gravity, stabilizing it so it follows the nose (like a rocket, this is why t...
- Mon Aug 13, 2007 3:00 pm
- Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
- Topic: Computers expose the physics of NASCAR
- Replies: 1
- Views: 5849
- Thu Jul 26, 2007 6:04 pm
- Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
- Topic: Impulse-based dynamic simulation library (IBDS)
- Replies: 94
- Views: 128255
Have you tried simulating complex closed loop mechanisms, such as the bricard mechanism? The bricard mechanism is known to be difficult to simulate due to the constraint redundancy. http://www.tu-chemnitz.de/ifm/english/e_ifm_ala4bsp_bricard.htm Just to be clear, it is supposed to move, correct (be...