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birthing particles based on velocity


cspears2002

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This is a continuation of my burrowing under a brick road project. However, since my focus is different, I decided to start a new thread.

I want to create dust as the bricks are being disturbed. I asked a colleague at work about this, and he suggested that I scatter points on the bricks and assign a velocity attribute to the points. Once the the velocity of the points reach a certain value, then they should birth particles.

I combined this suggestion with a hack I found in Craig Zerouni's "Houdini On the Spot" book (page 84). He shows a method where a Trail SOP is used to compute the velocity of some geometry and the velocity is promoted from a point attribute to a detail attribute. Then the user can use the detail() expression in the Source POP to birth particles.

However, this solution causes all of the points scattered across the bricks to start birthing particles! I want only the points on the moving bricks to birth particles. Any suggestions?

brick_road_v16.hipnc

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vop network wrapped around Curl Noise.

As an aside, Jeff - Curl Noise seems so handy for POPs don't you think it'd be a good idea for SESI to distribute a nice little Curl Noise Force / Wind vopnet OTL, as a companion to the other forces already available?

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OK I couldn't help myself.

Added some particle dynamics including a trivial vop network wrapped around Curl Noise.

wow, cool noise!!

quick particle test, rendered with PBR :)

particle_curl_PBR

EDIT: how can i get the correct orientation of the particles in the VOP?

jason

Edited by jason_slab
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I was checking out the VOP network. What does the Complement and the Clamps VOP do? I removed them and didn't notice any significant changes in the motion.

The complement vop does 1-input, and the clamp vop limits the input to a minimum and a maximum value.

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