How to move an 3DObject after it has been added to the SimpleUniverse

Engines, Libraries and Tools Java 3D
#1

Hi, i’m new to this Java3D stuff, and I was just wondering about something.

So far i can place a rotating colored square into a SimpleUniverse, but my question is how do i set its velocity after I’ve added it?

Perhaps i don’t know enough of Java3D to explain this correctly, so sorry about that

Thanks,
Weastmann

#2

You move objects by setting transform matrices in the tree above them.

If that doesnt make sense to you your going to have a LOT of trouble with 3D because its all based on vectors and transform matrices.

#3

Great thanks, so does this translation matrice only set the objects position, or can it be used to as a vector matrice?

Say we have this point:
(100,50)
How do I get the object to move from its origin to the point (100,50) with a speed of about 20 ms-1. If you could show me an example of how this would be done, that would be cool.

Thanks,
Weastmann

#4

A long time ago, in a galaxy far away, I wrote a tutorial that you may find useful.

#5

hey, i rember this tutorial from a while ago, but i had a problem when using it. For some reason during the “WalkDude” application, the purple guy always flies of the screen even if i just tap the forward key.

Is there a way to fix this?

Thanks,
Weastmann

#6

The transform tree of the scene graph describes the static position of everything at the scene at one point in time.

If you arent writing a game and can use “sloppy motion” where you cant count on wher it isin any given frame, you cna use Java 3D’s interpolators to interpolate a transform matrix between to values over time.

If youa re doing a game or some other kind pof program that requires rpecise control of motion then you need to write animation code that is called from a WakeupOnFrame(0) behavior to do the animation.

If you’ld like to see an example, you can grab my code for JNWN at jnwn.dev.java.net. Look at AnimationBehavior and how it works. I warn you its moderately complex because it handles a variety of animation manipulations, not just motions.

#7

Sounds like your framerate is faster than the original code expected - this is quite likely given that I wrote it 2-3 years ago now. Try reducing the the size of the forward step by a factor of 100 or so. There was also a problem with some processors and the J3D high res timer, I seem to recall I have found a workaround for this.

The questions you are asking are largely answered in that tutorial- if you follow through the text you should be able to work out why it’s not working on your machine and fix it from the source code.