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James Robinson avatar image
James Robinson asked ·

HtoA Alembic Procedural Normal Maps not rendering

Is there anything to consider when using normal maps and packed alembics? When I try to render with normal maps hooked up, they don't render, and don't show up in the Normals (N) pass. However, if I just unpack the alembic before rendering, they render as expected. It works fine with procedural noise, but not maps (which happen to have multiple udims. Not sure if it matters).

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James Robinson answered ·

For anyone in the future, I figured out it turns out since the object was exported from maya in decimeter scale, and then scaled down by 0.1 in Houdini, the bump2d magnitudes also needed to be scaled up by 10 in order to match the unpacked result. My guess is it has something to do with the scale of the alembic's intrinsic transforms. Anywho, it was just a matter of scaling up the bump (but only when packed)

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Martin Kindl answered ·

Normal maps dont need any rescale. Bump takes scale from alembic when using alembic procedural. It gets multiplied by the scale on OBJ level. If you use transform node on SOP level, no need to change bump. If yo uunpack your alembic, the scale from Alembic is no longer being used and it relays only on Houdini OBJ scale

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James Robinson answered ·

I should add

Houdini 17.5.360, htoa 4.2.0, Arnold 5.4.00

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