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Voronoi : shatters visible in render

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Hello world!  :)

 

I'm working on a school project which consists in a gun bullet going through a robot helmet. The modelling and animation has been made in Maya and exported as an alembic. I imported this alembic into Houdini and separated each object of the scene with the Pick option. I added a Scatter node and a Voronoi node on the part of the helmet I want to break. Then I did all the RBD stuff and the destruction works fine except I have a very annoying problem: the shatters of the helmet are too visible.

 

Some screenshots to help you understand:

 

Frame 1 (notice the shatters on the opposite side)

2enyvxg.png

 

Frame 34 (after impact)

6ghq3t.jpg

 

 

I'm a noob on Houdini so I might need precise explanations! :D I've been stuck on this for days and I'm getting desesperate...

 

Thanks in advance for your help!  :)

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This is just off the top of my head... but look on the Voronoi fracture node, find the checkbox that says something like "add inner edge detail", and un-check it.  That option will sometimes cause visible cracks in the surface.

 

And in case you're not... I'd recommend putting a 'switch' node at the end of your network. Use the original geometry up until the frame of impact, then switch to your shatter sim.  This will minimize the amount of time that the pre-fracture is visible before the actual shatter event happens.

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Attribute transfer normals from your original geo to the fractured geo, make sure the outside group exists and set destination group to outside. You may want to make sure your normals for inside are correct first.

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it also works to put down two vertex nodes after the fracture process.

 

In the first node set vertex normals to add normals

 

In the second vertex node set normals to cusp and set it to 30.  Play with that number if you need to.

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you should also use a switch node keyed to your DOP start time, this way u dont need to do anything extra before the sim, I also use a fuse sop so when pieces are together their surface is merged properly, together with transfering Normals from unbroken geo you should get proper results

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