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Particles Problem


Visual Cortex Lab

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Hi guys,

I've got a problem which i spent coupe of days on it.. without finding the solution.

I'm trying to create some "grass" which roughtly react after a char walk and falls around it.. (sorry for my poor english)... and I'm using a simple POP solution.. which basically copy a strand over the particles... randomize the strand for each copy.. and randomize transformations as well...

then the char collide with particles... which get bounced away ... the result is what i'm looking for.. but I'm encountering a problem which I'm not able to solve..

if you look at the scene and play a flipbook is easy to find but I'll try to describe here.

basic network...

- a volume that generate the particles where to copy the strands

- an animated (translation AND point position, like a shape animation or a OBJ sequence) sphere that acts like my char

- the strand with a point and a transformation nodes pasted from copy

the problem is that I'm orienting each strand based on the V vector of the particles... so that when they got collided the fly away with some motion on 'em and with "correct" orientation....

I use paste to randomize point position to get all different strands after th copy, and a transform to rotate the strand randomly as well..

- scenario 1 (no probs)

the colliding sphere (the char) have JUST translation, no point moving

everything runs fine.

- scenario 2 (probs)

the colliding spere (che char) have both translation and point randomized (like a OBJ sequence)

the problem is that once the sphere collide with a particle.. all others gets badly rotated as well... and with apparently no sense... like the vector of those uncollided particles gets badly calculated (which should be zero by the way 0,0,0)

sorry for this "engrish" post.. i guess the scene is much better to understand.

hope anybody find what i did wrong there.. my head starts to hurt after a long weekend on it :)

cheers

particle_copy_problem_1.hipnc

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I'm not quite sure I see the problem in your hip file. Just trying out the BYPASS_ME node bypassed and not bypassed, it seems to be that the particles are just being hit by sphere differently because it has polygons that are now aiming in undesired directions? Pick a POP network and a frame at which you notice the problem.

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...no ?...

ok I'll try to explain again .. maybe the hip files doenst how enought..

particle emitted from a sphere volume. static particles.

a strand of geometry (grid)

a collision object.. which is a geo sequence. (or a morphing geometry.. in both cases I have the problem.. if the geometry is just translating.. ther's no problem)

when the collision object collides with the particles... the strand, which are copied and normal oriented to those particles, starts to have random orientation IF their trans/rot/scale is pasted by the Copy and if the collided object is as stated above (morphing).

I'm using the velocity vector to get a normal for the strand orientation .. which should be 0,0,0 until a particle gets the collision ..

hope this helps a bit more... I'm sorry about my english .. I'll try to make a new scene once I fix my new laptop Linux setup problems :( (it doesnt like Fedora.. I had to go to Ubuntu... discovering that it have few problems.. damn)

cheers.

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......all right...

it seems I found a "cause" to the problem I'm having.. and seems not related to nor collision deformation .. or anything else.. but to the CLIPsop ... I did a simple scene which shows the problem ... bypass the CLIPsop to see the difference.

hope this helps

cheers.

particle_orientation_problem_1.hipnc

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