Hello

I'm working on a blast off type effect where smoke and fire are coming out of rocket engine. I've got the particles setup the way I want them, but what I' having a hard time with the shading. I can shade the entire set of particles, but I have two groups in there, one for the fire, one for smoke. I'm not sure how to assign different materials to different groups within the POP context

Thanks
Alex

You won't do that in Pops, you assign the materials to the groups in sop space.

So you mean that Pop groups are passed on to the SOP level? Do I need to create group operators at the Sop level or can I just used the groups that are created by POP nodes?

Thanks
Alex

Try it for yourself and see.

Apply group POPs and then see that those groups are also present in SOPs after the POP Network SOP. Same goes for attributes.

Thanks Jeff, I will work with that.

I'm looking for some good leads on texturing smoke and fire for a rocket blast off. Is there a good reference I could use?

Thanks again for the leads

Alex

hi Alex,

maybe this will help, it's a tutorial about creating smoke for a meteor.
After watching the 3D Buzz' Basic Shader Tutorial i really did understand the building of the shader and the results aren't that bad.
Of course you would have to tweak stuff to get you desired results.

http://studentpages.scad.edu/~rcampb23/houdini/tutorials/meteor/meteor_tutorial.html [studentpages.scad.edu]

another tutorial you could have a look at, is on the sidefx website itself:

http://www.sidefx.com/images/stories/tutorials/effects/working_particles/working_with_particles.pdf [sidefx.com]

so have fun with those lessons, i certainly did.

regards,

Manu

Awesome, that is exactly what I need. I'd rather not work with sprite, but I might aswell learn them…
Thanks!
Alex

As long as you render shadows with deapth maps instead of raytracing sprites are very fast to render.
so … let's see some results

Grid based fluids is the way most go for this. Just use the Smoke or Pyro Solver to set this up. Pyro has two leap-frogging rest volumes that do a decent job of sticking noise to the volumes for both upres and the pyro shader.

If you have your heart set on particles, there is an older tutorial on our web site on how to set that up:

http://www.sidefx.com/index.php?option=com_content&task=view&id=486&Itemid=132 [sidefx.com]

Uses now quite old school methods and done in H8 but should work in H10 if you know your way around a bit.

I'm interested in doing it with Particles to learn how to shade particles (but I'm also interested in shading volumes as a next step of my apprenticeship ).
I have a few tutorials about the Pyro solver, will see if I have time to learn it on this test.

I'm doing a class on Houdini at Gnomon in LA and I just need to master particles for now. The interesting thing is that we are using that exact rocket tutorial as a basis for the class (which is being taught in H10)

Thanks again for all the suggestions

Alex

So I tried creating POP groups within my POPnet, but no luck, I couldn't see them coming across in the SOP level.
I must be doing something wrong, as I have two group POPs branching out of my last node in the POPnet tree. They are assigned my existing POP groups. I tried to attach a combine node at the end of the tree, but i won't take two separate group nodes (or will but returns an error)

When I attach a material to the POPnet, no groups show up. Is there some other way to promote the POP level groups to SOP world? Or am I just missing a step?

Thanks
Alex

Branching out? Nope.

The Group POPs have to be in-line and in the POP chain all funneling down in to a single POP chain with the display flag on a POP after the Group POPs to have them after the POP Network SOP.

MMB on any POP will clearly show you if the groups have been created and if they have any particles in them.

Responded in the other post. You have to in-line them.

Combine POP is used to merge two separate Particle primitives as you would have to do when you split off some new particles.

For some reason the groups are not going through to the SOP level. I tried this with a file I created aswell as with a file I was provided in a different thread that used groups to have the split node create particles at a given time. Is there an example somewhere of using POP groups to assign different shaders to particles?

Thanks
Alex

To figure out if groups are actually being created in the POP network and are passed in to SOPs, use the MMB (Middle Mouse Button) on either the POP Network SOP or any subsequent SOP after that to inspect the geometry. You should see your groups listed there along with how many points are in each group.

As for assigning materials it seems that you can't use point groups to assign materials to particles (I will see if this is either bug or limitation). This is why you have to read the first paragraph to make sure that groups are in fact being created.

Assign materials by using two Blast SOPs using the point groups then two Material SOPs in primitive mode then merge together again.

See the example file.

Thanks a lot Jeff, the use of the Blast SOP is really interesting. What exactly is the Blast SOP doing aside from “deleting” a certain group? Does it somehow “convert” the particles to being SOP points rather than POP points (if such a question even makes sense…)

I did a test render of your scene and could not see the colors come through, although I saw you assigned two different colors pretty clearly. I copied the points to spheres to make sure Mantra had some geometry to render, and still the colors would not come accross. Copying sphere SOPs allows me to see the colors in the viewport, but still not in Mantra

I hope these beginner questions are not too annoying, I really appreciate your patience in explaining this

Thanks
Alex

Blast is just a quicker lighter version of the Delete SOP. I am simply deleting all the points in a group. Correction. I have the “delete non-selected” toggle on so the group field means “keep these” instead of “delete these”. I find this makes more sense in some situations.

As for not rendering, it did work for me in the attached scene file. Make sure to set the Material SOP to Primitives and NOT points. Particles with material attributes bound as point attributes doesn't work inH10.0.425 for me.

Feel free to post a scene file.

I am using an older version (x245). I will download the latest build and give it a try

Thanks
Alex

i was observing this thread,
Jeff thanks for the hipfile, it's very informatively!

regards,

Manu

So the rendering problem was solved by installing the latest daily build of Houdini

Thanks for all the help
Alex