Hi,
I have a simulation of particles orbiting the Y axis looking at a point (think globe) which is then copied to a geometry of a box.
What happens is that when I run the simulation, the particles tilt in the direction of it's movement. The only tilt I want is for it to look at a point. Can anyone give me pointers as to how to achieve this effect?
Need particles to stop tilting in simulation
5050 5 2- Mishari
- Member
- 3 posts
- Joined: Sept. 2009
- Offline
- Allegro
- Member
- 696 posts
- Joined: March 2006
- Offline
- Mishari
- Member
- 3 posts
- Joined: Sept. 2009
- Offline
I'm not too sure how to add a normal in Houdini
but for now, I've add an up vector to the bottom of my POP Network, changed the up vector type to vector and added the following expression:
cross(vector3($NX,$NY,$NZ),vector3($VX, $VY, $VZ))
Which gives an error “undefined variable” I'll keep working on it, but any help will be appreciated
but for now, I've add an up vector to the bottom of my POP Network, changed the up vector type to vector and added the following expression:
cross(vector3($NX,$NY,$NZ),vector3($VX, $VY, $VZ))
Which gives an error “undefined variable” I'll keep working on it, but any help will be appreciated
- Allegro
- Member
- 696 posts
- Joined: March 2006
- Offline
That would probably be because you have no normal
Are you trying to add this at the geometry level or during your simulation?
You can probably get away with doing this after the simulation.
You can use a point sop to add a normal, you'll probably want to do something like the beginning of http://download.sidefx.com/images/stories/tutorials/expressions/13_custom_attributes.mov [download.sidefx.com] to get a normal that is looking at your origin/centroid/specific point, only on a per $PT/$ID basis.
Are you trying to add this at the geometry level or during your simulation?
You can probably get away with doing this after the simulation.
You can use a point sop to add a normal, you'll probably want to do something like the beginning of http://download.sidefx.com/images/stories/tutorials/expressions/13_custom_attributes.mov [download.sidefx.com] to get a normal that is looking at your origin/centroid/specific point, only on a per $PT/$ID basis.
Stephen Tucker
VFXTD
VFXTD
- Mishari
- Member
- 3 posts
- Joined: Sept. 2009
- Offline
- Allegro
- Member
- 696 posts
- Joined: March 2006
- Offline
Unless you need the attributes *in* the simulation or for some reason can only acquire the attributes during the simulation, it is typically better to add them after the simulation. This way you can write the sim to disc, and do post processing that is easy to customize. Allows you to spend much less time redoing simulations.
You might be able to use the properties pop, or attribute pop to add normals if you insist on doing it in the simulation.
You might be able to use the properties pop, or attribute pop to add normals if you insist on doing it in the simulation.
Stephen Tucker
VFXTD
VFXTD
-
- Quick Links