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Complex Bool wall breaking

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Hello. I've been trying to solve this on my own for some time now but haven't been able to come to a good conclusion. If you have an idea how to solve this without following my current approach please also tell me, I'm very open for any idea that will help me to reach the desired result. 

I am trying to create an effect where I am able to take any kind of geometry (mostly architectural wall pieces, based on single tiles that have been merged) and 'break off' some of it's out hull to achieve this very typical, run-down wall look: IMAGE link

The steps I have currently are (see attached images)


Step1: The base mesh is a merged object made up of individual tiles. I'm fairly new to Houdini, so I might not have created these in an optimal way. Any suggestions on how to improve are very welcome. From these merged objects I get a bunch of groups that I am using later.


Step2: From the "base" group, which is just the facade without any of the other pieces I create a bunch of large voronoi clusters.


Step3: I chose one of the voronoi clusers and, since the object I used to create the voronoi clusers was flat I extrude it.


Step4: I try to apply a Bool SOP to substract the voronoi cluser from the original base mesh. It 'kinda' works, but there are many artifacts, and with no setting I am receiving a clean result. When I replace either the base mesh or the voronoi cluster with a simple geometry I receive great results, but both together are not working properly. There are many areas that I know could be problematic, but I've been unable to fix this. Is my approach spoiled alltogether? Should I do a different thing? I cannot create the windows after the bool, as I want to have a pool of many different facade pieces and then apply this breaking effect to a collection of them. Any advise is greatly appreciated!

I have attached the .hip file of course as well: bool_problem.hiplc


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Mmm the file you shared might be an earlier version, as the clean node gets rid of the "base", "base2" and "deleteOuter" groups, thus clashing with the next nodes, which use those groups. I grouped them in a quick & dirty way. In turquoise, the nodes that I either made or touched something within.

I think it comes down to the facade being extruded too small a distance. Increasing it from .03 to .3 delivers good results, I think. Also, I extruded a bit more the whole thing on top of that to achieve cleaner geometry; there is a version preserving the window frames, but note that this isn't a very procedural approach, as it requires you to carefully select what to extrude and what not, and the one eating away the window frames suffers somehow due to two edges being inset when extruding, which requires dealing with those specific edges with a fuse node. There probably is a cleaner way of getting rid of those.

Lastly, I included a VDB version, just in case you'd like to try something different. This should deal with anything you throw at it, however the geometry will be dirtier and it is a much more expensive method.


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here's my fix using extrudevolume so I know exactly what direction I'm adding thickness (then I have to add thickness in other dimensions by a slight increase in scale)...that's not too hard...what I have absolutely no idea about is.....in Boolean, I have to change it to Intersect........

SAY WHAT ??????? I hear you scream...

well .....it works...



Edited by Noobini

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