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Art Directed Wall Explosion

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Hey everyone, 

I'm trying to blow an object through a wall. I need a lot of control over the art direction. I have been doing my look dev in C4D where I can paint active vs passive objects. I can also have the active objects asleep until there is a collision detected. 

I have attached my working Houdini file. I haven't been able to figure out to paint active vs passive objects, so my workaround has been to alter the glue strength based on a color attribute that I created in the constraint network. This seems to work okay, but the wall get's knocked over when the collider goes through it. How can I pin this wall down to the ground? The tuts I've found all seem outdated for H16. 

Any help is most appreciated. Thanks!


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I can't see your file.

Some points

1. What you're describing IS painting an attribute. In this case you're painting the glue str, but you can do the exact same with the active attribute (which controls "passive" and "active" objects) 

2. RBD workflow changed (AFAIK) nothing in H16. What changed was the boolean, but that's not really related to the present situation

3. You can glue anything to anything, which means one way you can make the wall stick the ground is to glue the wall to the ground

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Have popped together a quick help file made in H16, though none of this is different for H15 (or whenever the new foreach was introduced). Usual disclaimer, different ways to do it and my way will almost certainly not be the best/most efficient/most vex heavy/most beautiful :D

The wall is wonky purely to demonstrate how pieces with an active value of 0 are exactly that, completely inactive. Gravity, collisions, etc, doesn't care. It also demonstrates the glue constraints working to hold the pieces in place until they're smacked into by that sphere. 

The foreach is a cleaning up/robustness thing. I'm actually unsure how the active attribute is transferred specifically when the geometry is packed as it will not exist on all points for that chunk - Perhaps some sort of average, in which case setting a high enough threshold in the if statement where the active attribute is set may be sufficient to ensure that chunk is active in the sim. The foreach however makes it much more visually obvious what is active and what isn't, and seemed to work better than bypassing it completely and upping the threshold (I didn't have time to test this though so feel free to fiddle and report back with your findings). 

Either way, now you can paint whatever you want to be active and whatever is white will move and what isn't will not. I didn't do anything to ensure the painted chunks make their way all the way through the wall as you can see but I need to get back to swearing at volumes now :angry:

Edit: Quick FYI, it can be way more straightforward to set your active attributes after you pack the geometry, and then you only have to worry about it being on the one point for that chunk. This can be easily done with a group sop done by bounding object, and placing other geometry where you want chunks to be active. Then you just need to run a wrangle on that group setting the i@active attribute and chuck it into dops. No painting, but way less nodes. 




Edited by adrianr
Added another example + images
  • Like 1

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I would do everything he did only I wouldn't do it in a foreach loop. Just paint more if you want more pieces added. Too slow if his geometry is heavy. 

Instead of painting you could simply group on the inside of a volume of a sphere or something. You can do this after you pack your geo too. 

You can also display an add sop that has "delete geo but keep points" and highlight your paint node which is above that add node. Your assemble node will be above your paint node. The add sop is only to see what is going on. When going into the sim you want to cut off the add node. 

I try to avoid for each nodes as much as possible. 

active paint.JPG

Edited by Tyfx567

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