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Feccand Buggery
03-30-2003, 01:32 PM
Hello everybody.
I'm trying to learn Xpresso but I have run into 2 problems.
I hope that you can help me with them.

1.
I have a problem with a typecasting from integer to float (real).
I want to connect PBorn.Birth Num -> Range Mapper.Input.
I tried using a Universal adapter but it doesn't work for me.
I might be using it wrong though. I don't find the documentation for that node very good.

2.
I made some colliding spheres with Xpresso but the precision is really awful. Can I force the expression to be evaluated several times for each frame? Like the motionblur or dynamics code.
If I turn up the framerate on the project to 300 instead of 30 it looks really good but that is a whole lot of raytracingtime just to throw away 9/10 of all frames :D

Pardon my possibly incorrect grammar but I hope that you understand what I'm trying to say at least.
Besides that I just want to thank you all for a very inspiring forum.

Regards / Feccand
Srek
03-30-2003, 05:28 PM
Hi,
Xpresso features aut conversion for compatible types. to convert between integer and float just connect the ports, it will be done automaticaly.
As to your second question, no you can't evaluate an Xpression several times. To solve your problem you can base the solution on the velocity of the objects and calcuate the point of collision even when it's between frames.
Collision detection however isn't one of the easiest problems and if the options of Xpresso (Collision and RayCollision node), Thinking Particles (PDeflector) and Dynamics do not suffice you will have to take a serious dive into simulation techniques and C++.
Regards
Srek
trfalk
04-10-2003, 08:59 AM
Sounds like you need to be working in nanoseconds, and not frames :) Would setting up a network of Xgroup evaluations all feeding into the parent Xgroup of the expression speed things up? (xgroups running in parrallel) Let me test it when I get home... this might be fun.

Can you post or email the Xpression for testing?
Katachi
04-10-2003, 09:04 AM
Originally posted by Feccand Buggery
2.
I made some colliding spheres with Xpresso

If you really only want to make spheres collide that shouldn´t be too hard. Just get the radius and check if any polygon or point is within the radius.

Best
Samir
trfalk
04-10-2003, 09:16 AM
Sounds like you need to be working in nanoseconds, and not frames :) Would setting up a network of Xgroup evaluations all feeding into the parent Xgroup of the expression speed things up? (xgroups running in parrallel) Let me test it when I get home... this might be fun.

Can you post or email the Xpression for testing?
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