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anicg

UDIMs in Houdini, how?

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I've done the UV's, a simple box, flat. Repeated several times.

How do I get UDIM tiles, with each segment (box) in a separate tile. Do I need to create any UDIM stuff before the UV layout?

geouv.JPG

uvs.JPG

uv1segment.JPG

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most straightforward method is to use UV layout SOP that can distribute uv islands automatically into arbitrary number of udims, based on some parameters available. or, if you want more specific distribution, you can create a udim primitive attribute that specify at what udim any particular primitive is supposed to end up and supply that into uv layout SOP. then you can also use more exotic methods like vex code or looping methods to distribute pieces of geometry into udims by some user specified rules. for this simple case thou, uv layout should be more than enough.

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Thanks. Let me start with the first automatic one, is this what you mean?

Pack into : UDIM tiles

Scale: Fixed

But these don't look like several UV tiles? do they?

is this udim.JPG

Edited by anicg

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it certainly does... right now you're using udims 1001 - 1050 if I count it right.

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45 minutes ago, davpe said:

or, if you want more specific distribution, you can create a udim primitive attribute that specify at what udim any particular primitive is supposed to end up and supply that into uv layout SOP. 

Cool, many thanks. Some go by twos and some are by ones (difference in resolution), how do I do the next step (in quote) of gently asking each one of the UV islands to go to a defined/separate tile? 

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well the most straightforward way seems to be to set the uv layout scale to slightly bigger number so two pieces never fit in a single udim (that is if they're not forming a single uv island).

other way is to generate a udim attribute beforehand and tell uv layout to look at that (Target Assignment > Target Atrribute). for example, if you want a single poly per udim, you can calculate udim from primitive number. in primitive wrangle, something like this would do the trick i suppose: i@udim = @primnum+1001; 

if your islands are containing multiple polygons, you can use Connectivity SOP in UV connectivity mode. that will generate 'class' attribute per uv island which can be used instead of primitive number: i@udim = i@class+1001;

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