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Slow down crowd in specific region

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Hi all,


I've found some Houdini crowd work put in my lap, but haven't really used Houdini in production for years. I've managed to sort through a bunch of issues thanks to you all here on the forum (thank you!), but curious how I can use volumes or paint maps to connect somehow to different forces like drag or the Pop Steer Speed Limit. I see they only have one input, not allowing me to try a mask field I read in another thread.

I know you can do things like in the street example so agents switch states, but it looks like I'm not getting animation clips or other cycles. I thought I could slow down the particles like using a volume axis field in Maya or something.

Thanks for any tips or tricks, I'm interested in learning more about particle/agent manipulation.


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Thank you SO much! You are so great for doing this, much appreciated. That is exactly what I was looking for.

I will go over the hip file to see how you put this together and see what I was missing in my Google search.

Thanks again!


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Hi Atom,

I've been looking through the example file, and it's great to learn about the pop group and pop wrangle nodes. But I think my wires are crossed, is there a way to get the agents to slow down in the box using the pop wrangle, and not switching states? I will ask if we can get some more anim clips, but I'm not sure if I can use state switching. I could be reading this network wrong (probably), just curious.

Thanks again. 

ETA: I see it looks like you're duplicating an agent and basically faking your way out of having to use another animation cycle. Cool trick for sure! So far I have the spiders changing state when they enter the volume, but they just stop and sort of look like they get squished. I'm thinking the difference might be because I'm using locomotive clips and not in-place?

Anyways, thanks again, having fun deconstructing the hip file.

Edited by dax3d
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Hi again,

It works! Works great actually. It was fun deconstructing your scene and applying it to mine with several agents. The squished spiders issue was because I copied the names mostly verbatim from your scene (saw I had to change them) and one node still had walk for clip name vs. 'character_walk' clip name.

Thanks again, this is a really cool example.

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Here is a variation on the scene where I have added two nodes, colorized green. The Agent Properties is placed after the crowd source to add some common useful attributes to each agent. Inside the DOP network, a CrowdObject is added which references the Agent Properties.

The net result is I was able to abandon the transition approach and just control velocity, in the PopWrangle and clipspeedmultiplier in the CrowdState. These two code blocks execute only when the agent is within the box area.


I'm still not able to control the @gait_speed directly from a wrangle, however...




Edited by Atom
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This is awesome as well, thank you again Atom.


I managed to add in multiple triggers for multiple bounding geo, and using the Crowd Trigger Logic node, it seems like things are working pretty smooth.

I'll go over this example, interested to see the various ways to achieve these results in crowds. Thanks again!


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