Lightmap unwrap improvements - prevent division by zero #113716

Sebastian Witt · 2023-10-14T11:48:54+02:00

Sebastian Witt commented

2023-10-14 11:48:54 +02:00

This is the first part of two improvements i want to propose to the lightmap unwrap functionality.
The second part can be found here: #113720

The changes are pretty self explanatory:

If a mesh has an ngon with a zero length edge it will throw a division by zero error.

My solution is to just check the calculated spans for almost zero values.

Attached is a test .blend to reproduce the issue.
In it select the cube and unwrap->lightmap pack.
The cube contains an ngon that was scaled to size 0.

This is the first part of two improvements i want to propose to the lightmap unwrap functionality. The second part can be found here: #113720 The changes are pretty self explanatory: If a mesh has an ngon with a zero length edge it will throw a division by zero error. My solution is to just check the calculated spans for almost zero values. Attached is a test .blend to reproduce the issue. In it select the cube and unwrap->lightmap pack. The cube contains an ngon that was scaled to size 0.

div_by_zero.blend

848 KiB

Sebastian Witt added 1 commit 2023-10-14 11:49:05 +02:00

db4ef98586 Prevent division by zero on small ngons unwrap

Sebastian Witt reviewed 2023-10-14 11:50:00 +02:00

scripts/startup/bl_operators/uvcalc_lightmap.py

						
				@ -116,3 +116,2 @@

				                for i, co in enumerate(cos_2d):

				                    self.uv[i][:] = ((co.x - xmin) / xspan,

				                                     (co.y - ymin) / yspan)

				                    if xspan < 0.0000001 or yspan < 0.0000001:

Sebastian Witt commented

2023-10-14 11:50:00 +02:00

Is there a standard "epsilon" value to use instead?

Campbell Barton commented

2024-01-11 00:06:01 +01:00

There is sys.float_info.epsilon but it's ~2.2e-16 and often too small to be useful.

There is `sys.float_info.epsilon` but it's ~`2.2e-16` and often too small to be useful.

Iliya Katushenock added this to the Modeling project 2023-10-14 11:50:40 +02:00

Iliya Katushenock added the

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Lightmap unwrap improvements - prevent division by zero #113716

Pull request closed