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How can I connect this pop network?


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hey, halion! it is a bizzare thing, i reconstructed your network and yes, it does turn black if you connect the pop to the merge. However, it renders perfectly fine, but if you want to avoid that altogether, add another merge sop and merge the product of your first merge with the pop. did the trick for me.

good luck!

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Hi there,

If you connect geometry with the Normal attribute into a Merge SOP, other connected geometry will turn black. The alternative is to append a facet SOP to compute Normals or delete all Normal attribute from any geometry before merging them.



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It'll work with a single merge SOP if you merge the pop in first. Point normals are the problem. The surface normals are fine, which is why it renders properly. Facet doesn't seem to help after the merge either.

As near as I can recon, and I'm by no means an expert....

The merge SOP basicly merges all this stuff into one object, right? When doing so it reorders all the points. It works fine when you give it the objects, but if you follow the objects with a mess of loose points, it's like the merge SOP doesn't understand where one surface ends and the next starts and doesn't know how to set up the normals properly, so all your objects are shaded black in the viewport. If you give it the popnet first, the merge SOP seems to have no problem working out the proper point order and everything works fine.

As for deleting normals... I wasn't aware that was even possible. I always though a normal was one of those fundamental things that every point and primitive *must* have in order to be drawn. Is it really possible to delete them?

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Crap I should've tried putting the popnet in first then the objects into the first mode after I found out thats how it worked in the second merge. :blink: Thanks for clearing me up with the merge sops it makes sense about how it works.

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Well, normals are the pointer vector attribute N. So to delete this attribute, there's 2 ways off the top of my head:

- Append a Point SOP and change it from Keep Normal to No Normal, or

- Append a Attribute SOP and add N to Delete Attributes in the Point page

Point normals are indeed needed for OpenGL rendering but if the N attribute does not exist, Houdini will just compute them on the fly for OpenGL using the averaged primitive normals.

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I agree with Jason in that the merge SOP should properly build normals for all other inputs once it detects normals on any of the inputs. This behaviour shoud be able to be turned off though.

It would be even nicer if the merge SOP gave you a yellow warning flag whenever it detects missing attributes on any of the inputs. It should also have the yellow flag if the merge builds any normals for one or more inputs indicating that it would be good to build normals for all inputs.

I really don't want the merge to build normals for me in the long run. If I remove the merge SOP at a later date on some geometry that it was building normals for or switch the merge SOP in and out of a chain in an asset and I was depending on them, it will take time to figure that out and is potentially more confusing.

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