Hello!
Relatively new to Houdini and have encountered an issue that I've not been able to google forth an answer too.

I'm experiencing some discoloration of geometry and strange/unwanted shadows after fracturing a pillar.
The shadows and weird looking normals seem to come from the voronoi nodes themselves when they try to create the inside geometry for the fragmented prices, the discoloration I am still unsure of there comes from, it only appears after the first voronoi node but I can't see any function that would cause this.

I've included a render frame displaying the issue in a rendered context as well as an image overview of my node tree.

Thank you for your time!



https://www.dropbox.com/s/wv2r9wbxurqlute/Issues_Marked.png?dl=0 [www.dropbox.com]

https://www.dropbox.com/s/ue4ni60hi23gllp/Issue_Nodetree.png?dl=0 [www.dropbox.com]

Ahh, that old chestnut. I'd love a definitive answer, but I suspect each situation is different.

Looks like you may have two issues, normals incorrect (causing the weird shading in the lower parts of the pillar - the renderer is trying to smooth over the edge of the fracture), and missing faces or similar causing the upper cracks.

Fixing the normals - drop a Normal SOP or (failing that) a Facet SOP in after the for_each loop. The Facet SOP has a Cusping angle option somewhere in there that lets you choose what angle faces need to be at for their edge to be considered a crease.

Fixing the missing chunks - could be down to the topology of the pillar (can't tell from here); you may be able to just tit about with the Scatter SOPs' seed values to try a different arrangement of points for the Voronoi to work with. May need to divide up the pillar a bit more first.

I'd love someone a bit more experienced to chip in - this is not uncommon with bools and fractures, and most of the time I just play around with things until they look fixed, but it'd be nice to have a simple checklist to go through

howiem
Ahh, that old chestnut. I'd love a definitive answer, but I suspect each situation is different.

Looks like you may have two issues, normals incorrect (causing the weird shading in the lower parts of the pillar - the renderer is trying to smooth over the edge of the fracture), and missing faces or similar causing the upper cracks.

Fixing the normals - drop a Normal SOP or (failing that) a Facet SOP in after the for_each loop. The Facet SOP has a Cusping angle option somewhere in there that lets you choose what angle faces need to be at for their edge to be considered a crease.

Fixing the missing chunks - could be down to the topology of the pillar (can't tell from here); you may be able to just tit about with the Scatter SOPs' seed values to try a different arrangement of points for the Voronoi to work with. May need to divide up the pillar a bit more first.

I'd love someone a bit more experienced to chip in - this is not uncommon with bools and fractures, and most of the time I just play around with things until they look fixed, but it'd be nice to have a simple checklist to go through

Thanks for the reply howiem!
Most of the issues I was experiencing were only my own doing. Or rather two year younger me just starting out 3d modeling not giving two shits about something called topology XD
Once I opened it back up in max I had a small shock for how bad it was. Suffice to say that having a clean, or at least not intersecting into each other across half the god damn, model is the preferred place to start with fracturing. Cleaning it up has fixed over ninety-five percent of my other problems as well.
The only thing remaining is a very, very slight normals looking problem and a much less visible piece being slightly discolored. I'm not even sure if I am going to fix too much on it since I am planning on using a switch node for my geo anyways and I don't think it will be noticeable, never the less I'm including a photo of how it looks now and if anyone can tell me what I've done to cause this little thing to happen or how I can fix it I'd still love to hear about it for future reference!

What I suspect to be a normal issue is marked with a red circle, and what I describe as a “slight discoloration” is marked with a green circle.

I have already tried the normal SOP, as well as the facet SOP you suggested, and I've tried the old vertex sop that also has a cusp angle setting and unfortunately no luck.

Thank you!