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Baking from thin object makes margin inside UV island too
Open, Confirmed, MediumPublic

Description

System Information
Operating system: win7 x64

Blender Version
Broken: 2.80 (sub 47), 40412499433e, 2019-03-09 16:19

Short description of error
Bleeding margin go inside island if baked emmiter-mesh is not cover all.

how to reproduce

Open file:
Bake from WR to Recipient twice:
at first with 6px margin and option clear image,
then change color of WR`s emmision, without clearing image and with 0px margin.
You will have such result:

Margin made is only for filling seams (especially when mipmap shrinking textures).

File:

Details

Type
Bug

Event Timeline

Sebastian Parborg (zeddb) triaged this task as Confirmed, Medium priority.

As it says here: https://docs.blender.org/manual/en/dev/render/cycles/baking.html?highlight=ray%20distance#additional-options
The margin should only extend from the border of the UV islands. But it seems to just extend from the alpha border instead.

This was working correctly in Blender Internal. There is an important difference between the way "Selected to Active" bakes work in Blender Internal vs. Cycles: Blender Internal would render the active object into the bake map, whereas Cycles does not. That might be the source of the problem described here; it's possible that BI and Cycles are using the same approach to render the margin around the baked result, but because Cycles doesn't render the active object in Selected to Active mode, that baked result doesn't match up with the UV islands.

I really hope that makes sense. Maybe some images will help:

Blender Internal, Selected to Active, Margin 0:

Blender Internal, Selected to Active, Margin 64:

Cycles, Selected to Active, Margin 0:

Cycles, Selected to Active, Margin 64:

It would be great if we could get a checkbox to enable or disable rendering of the active object into the baked map, but I guess that's more a feature request than a bug report. Anyway, what we need is for the margin to render around UV islands, not around baked details that don't reach the edges of the UV islands.