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Face Extrusion With Chops (apply Channel Data?)


Fomal

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Hi there ,

I've been working on a sound driven animation using chops. Works pretty well and got some good deformation results for my objects.

The chop network itself works well and uses some generators in combination with some other data (oa audio) to drive the P or N values of my geo. (or N in and P out)

What I see as a wave in the motion graph is perfect. (right before it gets loaded in the channel sop).

My problem is that I don't want the chops to influence the entire geo but drive a face extrusion based on a selected group of faces. The chops use the selected predefined group of faces to apply an extrusion on. Would anyone know what to load into the geo chop (Position?, Normals?) and how to get the chop channels onto the selected faces? And then use the channel data to extrude them?

The tests i did before can be found here:

sim_test1

sim_test2

Any help would be appreciated!

Cheers Coen!

Edited by Fomal
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Cool Effect!

I think the root of your delima isn't a CHOPs issue but a SOPs issue. Once it's in CHOPs it's very hard to work with geometry, this makes sense since CHOPs are for editing channels. You could set up an elaborate system for selecting certain vertex channels in CHOPs by name or number etc, but my recommendation would be to use a combination of soft-transforms and blends with more basic parameters.

For your question, you might try copy-stamping the extrude value with a chop-animated point attribute, if they are all quads in your model you could try some stuff like copy-stamping an extrude on a box, then matching the bottom box position to the base positions of your origional mesh and the top point positions aligned to a normal etc.

Also for selective chop blending, you can set up your own blend in SOPs with the paint attribute, and pipe the full effect along with the original into a point sop and blend by your painted attribute.

Edited by andrewlowell
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Done some tweaking and tried to apply edward's solution. This works fine but doesn't give any random extrude values. Every group uses the same extrusion length. I want the randomness (and smoothness) that i get when i use the channel sop but more control over the extrusion (direction for example)

Strange thing is that when you load the chop data in a channel sop it deformes the entire geo. So I tried to apply it only to a set of points based on a selection. Result is that you get random extrusion but every face disappears into the geo. (goes in the wrong direction). I'm going to try the copy sop suggestion but it's hard for me to follow how to exactly do that. What do you exactly mean by a "chop animated point attribute"?

thanks in advance,

Coen!

Edited by Fomal
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Thanks for the support Andrew,

I sorted it out. Using an export chop to drive a face extrusion and in sop level I added a sort sop to randomize the surfaces. With a primitive i can randomize the extrude length with a basic expression. Now I can render my track(audio) out in different layers and let that drive different faces with enough random extrusion!

Cheers Coen :ph34r:

PS: For anyone who's interested. you can check the test I made here: http://www.connexmade.blogspot.com

It's a basic sphere with the system applied to it.

Edited by Fomal
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  • 1 month later...
Thanks for the support Andrew,

I sorted it out. Using an export chop to drive a face extrusion and in sop level I added a sort sop to randomize the surfaces. With a primitive i can randomize the extrude length with a basic expression. Now I can render my track(audio) out in different layers and let that drive different faces with enough random extrusion!

Cheers Coen :ph34r:

PS: For anyone who's interested. you can check the test I made here: http://www.connexmade.blogspot.com

It's a basic sphere with the system applied to it.

Hi,

I just came across this post. I am trying things out with chops, and was curious about how you ended up doing that. Did you put every face in a group of its own? Did you create an attribute defined by the chop channel? I am still trying to figure it out, and so far I am thinking towards making each face a group and applying the chop in the form of an attribute to the extrusion multiplied by a random value. Am I thinking this out correctly? Is there a way to control individual faces the way you can control individual points?

If you could post your HIP, that would be great!

Thanks,

Ilan

Edited by wick3dParticle
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  • 2 weeks later...

Hey Wick3dParticle,

Sorry for my late reply. Didn't check the topic for some time.

But you're definitely thinking in the right direction, only I didn't group every face. What I did was generate a channel for each face and by using a copy sop translate this data back on top of every primitive. But within the chop network I made sure every channel was slightly different then the other. So you get nice random motion. In the end this gets copied onto the z channel of you polyextrude sop and mapped across the surface using the copy sop.

I also made sure that it automatically updated the number of channels once different geo was used.

I made an asset out of this, you can download it here:

http://connexmade.blogspot.com/2008/02/minimoog-asset.html

Just plug something in and check what I've done. If there are any further questions just let me know.

Cheers Coen

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Hey Wick3dParticle,

Sorry for my late reply. Didn't check the topic for some time.

But you're definitely thinking in the right direction, only I didn't group every face. What I did was generate a channel for each face and by using a copy sop translate this data back on top of every primitive. But within the chop network I made sure every channel was slightly different then the other. So you get nice random motion. In the end this gets copied onto the z channel of you polyextrude sop and mapped across the surface using the copy sop.

I also made sure that it automatically updated the number of channels once different geo was used.

I made an asset out of this, you can download it here:

http://connexmade.blogspot.com/2008/02/minimoog-asset.html

Just plug something in and check what I've done. If there are any further questions just let me know.

Cheers Coen

Coen Thanks a lot dude! I am taking a look at your OTL, and trying to keep up with everything. I am fairly new to Houdini, but I think Im getting the general picture here.

The OTL works great!

~Ilan

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Coen Thanks a lot dude! I am taking a look at your OTL, and trying to keep up with everything. I am fairly new to Houdini, but I think Im getting the general picture here.

The OTL works great!

~Ilan

Great to hear that it works out for ya!

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Hi Simon,

Thanks for your kind words! It was a group project for school (bournemouth university), worked on it for about 8 weeks. First couple of weeks were spend on developing the assets, filming, tracking etc. The rest of the time we spend applying the little systems we came up with, shading and rendering. All with all a lot of fun to work on. Gave us a good idea of what Houdini is capable of (a lot!)

We haven't exposed it anywhere yet. Normally our tutors take care of things like that but if people are interested i'll make sure it get's posted on the suggested forums! Would definately be nice!

PS: the edit shown on the blog is an old one. There have been some changes since. I'll make sure the new one's up there this week...

Cheers Coen!

Edited by Fomal
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