Search found 861 matches

by Dirk Gregorius
Tue Mar 10, 2015 2:21 am
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Rubikon : Valve's physics engine for Source 2
Replies: 8
Views: 69999

Re: Rubikon : Valve's physics engine for Source 2

No, everything is running on the CPU. Physics is a big part of gameplay, so I don't see any physics simulation running on the GPU in the near future.
by Dirk Gregorius
Mon Mar 09, 2015 11:38 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Physics Engine Questions (GJK+EPA, SI/PGS)
Replies: 2
Views: 21879

Re: Physics Engine Questions (GJK+EPA, SI/PGS)

This question is way too long. You need to break into smaller parts.
by Dirk Gregorius
Mon Mar 09, 2015 11:37 pm
Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
Topic: Rubikon : Valve's physics engine for Source 2
Replies: 8
Views: 69999

Re: Rubikon : Valve's physics engine for Source 2

Rubikon is our custom rigid body engine we use in Source 2 now. There aren't really any secrets there. What are you questions?
by Dirk Gregorius
Sat Oct 04, 2014 5:57 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Any smart ideas on contact resolution priorities?
Replies: 8
Views: 16019

Re: Any smart ideas on contact resolution priorities?

Well, a good example would be a hinge. You usually solve the motor first, then the limit, followed by the two angular constraints and finally the three linear constraints. Obviously you want this order as the motor can press on the limit and then as the limit comes after this and cancels the motor a...
by Dirk Gregorius
Fri Oct 03, 2014 2:26 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Any smart ideas on contact resolution priorities?
Replies: 8
Views: 16019

Re: Any smart ideas on contact resolution priorities?

I have more of a block solver. So it looks like this:

for ( n iterations )
{
for_each( dynamic_contact c )
c->solve();

for_each( static_contact c )
c->solve();
}
by Dirk Gregorius
Sun Sep 28, 2014 4:17 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Any smart ideas on contact resolution priorities?
Replies: 8
Views: 16019

Re: Any smart ideas on contact resolution priorities?

Randy is right. You should sort your contacts such that static contacts are always solved last. This way you reduce chances that stuff gets pushed out of the world. For doors I would use motors instead of kinematic bodies. You compute a motor force that will follow the animation. A kinematic body ha...
by Dirk Gregorius
Mon Sep 22, 2014 10:57 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Inequality Constraint in PBD
Replies: 4
Views: 12895

Re: Inequality Constraint in PBD

Conceptually very much like equality constraints. It depends on the type
by Dirk Gregorius
Mon Sep 22, 2014 5:21 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Inequality Constraint in PBD
Replies: 4
Views: 12895

Re: Inequality Constraint in PBD

You simply skip over the constraint if the inequality is satisfied.
by Dirk Gregorius
Thu Jul 17, 2014 12:11 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Strategies for dealing with non-incremental broadphase
Replies: 4
Views: 10533

Re: Strategies for dealing with non-incremental broadphase

I don't create pairs at that point. The proxy movement is cached and when you step the physics world the first thing you do is to create new contacts by iterating over the cached proxies that have moved. The general concept with a dynamic tree broadphase is different from a SAP. The SAP has begin/en...
by Dirk Gregorius
Wed Jul 16, 2014 9:55 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Strategies for dealing with non-incremental broadphase
Replies: 4
Views: 10533

Re: Strategies for dealing with non-incremental broadphase

I update the proxy in the broadphase immediately to avoid the problems you described, but I don't compute contacts directly. For hitboxes I don't add them into the physics broadphase at all. Especially on a server/client structure you don't want to rewind those. And even in general it makes sense to...
by Dirk Gregorius
Wed Jul 09, 2014 2:16 am
Forum: General Bullet Physics Support and Feedback
Topic: Spring daming in bullet
Replies: 10
Views: 22458

Re: Spring daming in bullet

I don't think so. The code sets the target velocity and maximum force of the limit in the constraint. This indicates to me it goes through the constraint solver which will try to reach the target velocity. A PD controller would just compute the force and use the ApplyForce() interface of the body. I...
by Dirk Gregorius
Tue Jul 08, 2014 4:35 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spring daming in bullet
Replies: 10
Views: 22458

Re: Spring daming in bullet

I am wildly guessing now, but maybe Bullet uses motors. Essentially you can have a motor working on free axis of joint. The motor is defined by a target velocity and a maximum force to reach that velocity. E.g. you can define a target velocity of zero and a maximum force based on the joint geometry ...
by Dirk Gregorius
Tue Jul 08, 2014 4:28 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spring daming in bullet
Replies: 10
Views: 22458

Re: Spring daming in bullet

Sorry, I don't know the internals of Bullet. I think there is a path in Bullet that calls into the ODE quickstep function. You can check there and see how the constraints/joints are setup.
by Dirk Gregorius
Wed Jul 02, 2014 8:48 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spring daming in bullet
Replies: 10
Views: 22458

Re: Spring daming in bullet

I assume Bullet uses some kind of soft constraint to model springs. Maybe this explanation in the ODE gives you an idea: http://www.ode.org/ode-latest-userguide.html#sec_3_8_0 Erin Catto gave a presentation about soft constraints here: https://box2d.googlecode.com/files/GDC2011_Catto_Erin_Soft_Const...
by Dirk Gregorius
Wed Jul 02, 2014 5:10 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: A fair comparison between Bullet and PhysX
Replies: 3
Views: 12024

Re: A fair comparison between Bullet and PhysX

Well first of all I would you prefer you to be more explicit of what you are actually testing. So the topic of the post should have been "cloth vs triangle mesh collision comparison". Your topic suggested (at least to me) a full PhysX vs Bullet comparison. Also if the intention of your tes...