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PrestoChung

Member Since 06 Jul 2009
Online Last Active Today, 04:17 AM

Posts I've Made

In Topic: Collision detection

13 June 2016 - 05:47 AM

if you have line triangle you can get line prism by testing the line against each of the 8 triangles making up the prism (1 for each end, 2 for each side)


In Topic: Contact tangents

03 January 2016 - 11:34 PM

Thanks for the pointers, I was going to modify my post to mention that I do use GJK already for distance and penetration calculation, but it does things pretty minimally so it usually returns a point/face as nearest features in a resting scenario.


In Topic: Contact tangents

03 January 2016 - 08:27 PM

So it turned out I was looking at the Catto "Iterative Dynamics" paper, which is a bit more advanced than this scenario, and actually what I had been using before was Catto's GDC2006 powerpoint, which I had previously compared to Bender and Schmitt and found to be essentially the same, although Catto goes into picking points on boxes and some other tricks such as a 'bias' velocity.

 

Then I would say it's time to add more contact points, but I have general meshes, not only boxes. Does anyone have any pointers for finding contact points on a general surface? I'm guessing the brute force approach is just searching along the surface normal and comparing dot products.


In Topic: Contact tangents

14 December 2015 - 08:21 PM

I'd say do option 1. The tangent vector is for applying contact friction, so surely it has to be calculated from the relative velocities of the contact points? I had a read through the paper and it seems to me that the tangent vector is described in the middle of page 4, as this.

That's quite a nice, readable paper :-)

 

That is the tangent used for collision response, the tangent for contacts is described on page 6.


In Topic: Position constraints converging slowly (contacts)

10 September 2015 - 06:43 PM

Oops, actually the target range was 0.0001 (edited the original post to fix this) which is 1/10 of the collision tolerance (0.001). Seems I can get away with 0.0004 (7 iterations) but after that it starts going up rather quickly (0.0003 -> 28 iterations, 0.0002 -> 70+ iterations). Hopefully that will be stable enough for stacking.


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