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Member Since 01 Jan 2004
Offline Last Active Yesterday, 02:03 PM

Posts I've Made

In Topic: Rotating collision boxes

10 October 2014 - 09:15 AM

If you convert your vertices into world space and then do the collision checks between the player and the shape, you will need to transform N vertices (N = 4 for your rectangle)


If you convert your player position into the space of the object you only need to do one transformation. Then if there's intersection you just need to do one (or a few) transformation(s) to get the result back into world space.


If your sprites are represented by more than a few vertices, that's a big saving.

In Topic: Havok for dynamic animation like Euphoria?

09 October 2014 - 10:55 AM

Euphoria isn't a physics engine. It's a system that drives a physics engine to procedurally generate animations that obey (at least by default) physical laws. 



I've seen lots of academic versions published, mostly at SIGGRAPH. We developed our own in-house over the course of several years; it is not an easy problem, as you can imagine. I'm not aware of anything off the shelf, let alone open source, that is able to do any kind of physics driven character movement.


Euphoria is now available "off the shelf": http://www.naturalmotion.com/middleware/euphoria/ It used to be available only as in a co-developer sense (i.e. we would work with developers to integrate our technology in a bespoke way), but since Morpheme 5 it is available as an additional component to the Morpheme animation system http://www.naturalmotion.com/middleware/morpheme/

In Topic: Particle fluid simulation

09 October 2014 - 09:48 AM

It's worth considering that whilst the equations in SPH might be "physically based", the behaviour in reality, certainly with a naive implementation, can be rather bouncy, very sensitive to things like the timestep (i.e. you have to tune your parameters for the timestep), and a tendency towards being unstable. I haven't done anything on this for quite a few years now, so may be completely out of date. However, it may be that you can get results that look more physically plausible in spite of being less physically based by using more ad hoc methods - for example see Dennis Gustafsson's blog posts.

In Topic: collision with frictions dealt using tangent impulses

01 October 2014 - 04:09 AM

I'd advise using almost any resource apart from that Bourg book.

In Topic: Simulation of drag in flightsims

22 September 2014 - 10:46 AM

I don't think it's that surprising. Probably all "normal" symmetrical aerofoils, when viewed across the whole range like this, will look fairly similar (and all fairly similar to a flat plate). However, the choice of aerofoil for a plane will depend on really small details - e.g. just a tiny difference in drag around the angle of attacks you expect in normal flight will be important for fuel economy/glide slopes, and how it behaves in a stall will be important for safety. The symmetric tear-drop shape is there to minimise drag at low angles of attack, not to maximise lift close to the stall. Also, there will be additional constraints - e.g. needing to be a certain thickness for structural reasons.