Hey Houdini dudes,

I'm doing a DOP's based project to blow up a building (you might know that from the amount of questions I've posted about it so far!). I have prefractured my geometry and I am currently doing test simulaitons. As I am now thinking about the rendering stage I am coming up with more specific queries. Firstly, what is the accepted method for disguising the fractures on pre-fractured geometry before it explodes? In a simple tutorial I saw that after object merging the simulated geometry, one method is to place a fuse SOP and then assign a VEX Clay shader to the geometry. This seemed to work well for the simple geometry of a sphere smashing but my building is much more complex and is prefractured into around 2000 pieces. When I try this it doesn't seem to work fully, many fractures are still visible. When I do the diffuse pass I know my textures will do some work to disguise these fractures, but I'm thinking primarily about my ambient occlusion pass. Are there any other tricks to help this issue?

Thanks all you DOP's masters……

Off the top of my head, and depending on exactly how the animation and camera pan out, I'd at least investigate the CG equivalent of a jump cut - render the nonfractured building(s) up until fracture, then replace with the first frame of simulation. Now of course that alone may not cut it due to a desire to not have the entire building suddenly pop into a fractured state, maybe you want it spreading out from a central stress point. However, if you examine real world building demolitions(and I strongly recommend you screen and re-screen these as much as you can stand if you haven't already), you'll see that you might be talking 2-5 frames, at *most*. I would overlap the renders, and reveal the fracturing in compositing.

That's very much a non-elegant, terribly un-clever, not-impressing-your-friends with your OP knowledge approach. Also, the sort of one that gets actually used in production the most often.

Additionally, since you're controlling everything in CG, you can do useful things like render out animated reveal mattes(perhaps noise-based) with the cam move burned in, to make the compositing easier.

Cheers,

J.C.

I see what you're saying. It had occurred to me that I could do this kind of ‘non-3D’ approach, using an animated rotoshape in Shake to reveal the fractured version of my building geo as it begins to explode. I think you're right that this would be the most effective approach…..thanks for the advice.