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Mixing materials by UV-color makes glitches
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Description

System Information
Win7 x64
GTX 460

Blender Version
Broken: 2.73a

Short description of error
http://s30.postimg.org/er7rhhjr5/screenshot_102.png
This glitch appears, when i mix two materials (Blender render) using vertex color.
http://s30.postimg.org/3swhzav5t/screenshot_103.png

Here is an example file.You can use any textures.

Details

Type
Bug

Event Timeline

Maxim Tkachenko (maleficmax) created this task.
Maxim Tkachenko (maleficmax) raised the priority of this task from to Needs Triage by Developer.

Some details, I just noticed.
It happens only when I mix different UV channels

Antony Riakiotakis (psy-fi) triaged this task as Needs Information from User priority.

The glitch probably happens due to a bad unwrap.
Generally having UVs extend too far away or UV faces being too small can cause issues due to precision. This is not a problem of the material but a limitation of number representation in a computer. We might be able to address this (or not, depending on how extreme the use case is ) but we would need the a file with the whole mesh to see how it behaves under unwrapping.

Campbell Barton (campbellbarton) closed this task as Archived.EditedMar 9 2015, 5:52 AM

UV coords Y value is set at -41266 while there is no rule about the range of UV coords, really large values will give issues.

Best pack the UV's and locate them close to the center.

(note: this did expose a bug in our UI though, fixed rBc44f489d24a3075e978a0b4b499371fcb3803670)