trueaxis.com

[Mark Tanner]

Hello Luke,

I am converting an existing game to use TrueAxis, so I am coming across several (luckily small) questions. Surprisingly it was possible to get TrueAxis working near perfect in less than one day Great stuff!

In any case, here are the things I'm wondering about. Looks like a lot but each issue is pretty straightforward:

1. Unit/world scale. If a graphics engine uses 1 inch/unit, would TrueAxis scale well or would it be better to convert to 1m/unit and back when getting TrueAxis' transforms? In a inch/unit world, the sizes and gravity are a lot larger.

2. The game environment is city-type (many box-like buildings around 10m WxHxD). To create the 'floor' so that no objects fall through, would it be better to use one big poly (2 tris) say 500mx500m or split this up into several smaller polygons? I'm wondering since one large poly would be very different in size to the rest of the city's meshes.
(BTW I'm adding all of these meshes and the floor to the one AABB mesh like as advised in the help file.)

3. To play sound fx on collisions, I understand to use the recent collision list inside the dynamic object. But what would be a typical way to use the collision's info to determine a large enough collision took place to warrant playing a sound effect? I see that some collisions cause an intersection depth of 0.0f - 0.5f, some a very small impulse, etc. Should I do a value of depth*impulse to determine a collision's 'strength' or is there a better way? Basically not sure which collision info members are best to use.

4. Since the game engine is in a working state, I need to ragdoll existing bone-animated characters. This is a bit different from the ragdoll sample.

The characters are already animated in some pose and need to be converted into a ragdoll without too much change in their pose.
I got this working fine except I'm not sure about some of the joints parameters:

For a socket joint, the center normals, do these point away from the bone towards the joint? For example taking a typical upper/lower leg setup, does the lower leg normal point towards the knee joint or away from it along the bone?

For other joints, the 'm33DefaultRotationOfOtherObject' matrix, is this the local(?) bone matrix at character creation time or at the time of converting to ragdoll?

5. In the ragdoll sample, I see that it is ok to set the collision exclusion id's even before that particular dynamic object has been assigned an id? Just checking.

6. Limiting rotation. Imagine shooting a barrel in a game world. The first hit will move and rotate it a bit. But if you keep shooting at it while not yet at rest (for example while in the air), you can get it to rotate at too high velocity. How can I limit this so that it won't look like spinning too much?

7. Does 'debug' rendering the AABB mesh work in release mode? I seem to be able to render it compiling in debug mode but it crashes in release mode. Rendering the dynamic objects works in both it seems.

8. When deleting jointed objects, do I first ->release the joint then the two dynamic objects?

9. Finally, I sometimes see jittering of dynamic objects when they hit the floor. For example a box will almost come to rest but then jump around a bit. Can I prevent this without having it come to rest too quickly so that it looks dampened?

Thanks for taking the time for this!

Mark

[luke]

Thats a lot of questions...

I'll trie to answer everything.

[Mark Tanner]

Luke, thanks for the answers. I have been rewriting the code taking these into account.

The only issue left is still playing sound fx for collisions. For example, a barrel rolling along the floor generates a lot of collisions; I check the impulse and also the velocity and determine if a sound effect should be played, but this still sounds a bit too random.

It must be a combination of impulse, velocity, etc. Can you think of any better way to determine a collision?

Thanks!

[Ultrasauce]

Yeah, i'd have to agree. I'm playing with it a bit and I'm finding that although TA has proven to be awesome, I can't figure which way is best for sound integration.

Any tips or recommendations, Luke?

[luke]

Intuitively I would think the best way to choose whether a should should be played would be to check how much velocity has changed between frames. This way the sound will play baced on the change in movement which should make sence to the person watching. Thats how I would try to do it.

[Ultrasauce]

how about collisions... such as a clanking sound when a metal barrel gets hit by a bullet?

[Guest]

I'd use the velocity change, then check the list of collisions to what surface caused it.

The main problem with checking individual collisions alone is that if you have a box underneath a heap of stacked boxes, it will recieve large impulses, but you don't want a sounds played in this case because no impact has taken place.

I supose you could try to calculate the change in velocity at each collision point along the collision normal, that might be more usefull for sound intergration.

[luke]

That guest post was from me. It seems that sometimes when I log on to the forum I don't actually get logged on.