Fix #112018: increase AgX LUT resolution #113253

Nathan Vegdahl · 2023-10-04T19:29:00+02:00

Nathan Vegdahl commented

2023-10-04 19:29:00 +02:00

AgX exhibited some banding-like artifacts that were due to being
approximated with a 3D LUT. This commit resolves that by increasing
the LUT resolution enough to mitigate the artifacts and make them
unnoticeable.

Additionally:

The previous LUTs were written in a space-inefficient way, using
e.g. "0.000000" instead of "0". The new LUTs are written more
efficiently, avoiding quite as dramatic a file size increase as
usually accompanies 3D LUT resolution increases.
The previous LUTs included output values greater than 1.0, which was
both incorrect for a tone mapper, and also pointless since Blender
immediately clips them anyway. The new LUTs clip to 1.0. This also
allows the more efficient writing to squeeze even more space savings
out of the LUTs.
The previous inverse AgX LUT contained NaNs. Those have been
replaced with 0.0 in the new inverse LUT.

Note that due to discrepancies between the LUTs previously provided
to Blender and the AgX scripts that were later published, the color
transform in these LUTs are slightly different. But they are close, and
equivalently good.

AgX exhibited some banding-like artifacts that were due to being approximated with a 3D LUT. This commit resolves that by increasing the LUT resolution enough to mitigate the artifacts and make them unnoticeable. Additionally: - The previous LUTs were written in a space-inefficient way, using e.g. "0.000000" instead of "0". The new LUTs are written more efficiently, avoiding quite as dramatic a file size increase as usually accompanies 3D LUT resolution increases. - The previous LUTs included output values greater than 1.0, which was both incorrect for a tone mapper, and also pointless since Blender immediately clips them anyway. The new LUTs clip to 1.0. This also allows the more efficient writing to squeeze even more space savings out of the LUTs. - The previous inverse AgX LUT contained NaNs. Those have been replaced with 0.0 in the new inverse LUT. Note that due to discrepancies between the LUTs previously provided to Blender and the AgX scripts that were later published, the color transform in these LUTs are slightly different. But they are close, and equivalently good.

Nathan Vegdahl added 1 commit 2023-10-04 19:29:15 +02:00

Fix #112018 : increase AgX LUT resolution 3105870972

AgX exhibited some banding-like artifacts that were due to being
approximated with a 3D LUT.  This commit resolves that by increasing
the LUT resolution enough to mitigate the artifacts and make them
unnoticeable.

Additionally:
- The previous LUTs were written in a space-inefficient way, using
  e.g. "0.000000" instead of "0".  The new LUTs are written more
  efficiently, avoiding quite as dramatic a file size increase as
  usually accompanies 3D LUT resolution increases.
- The previous LUTs included output values greater than 1.0, which was
  both incorrect for a tone mapper, and also pointless since Blender
  immediately clips them anyway.  The new LUTs clip to 1.0.  This also
  allows the more efficient writing to squeeze even more space savings
  out of the LUTs.
- The previous inverse AgX LUT contained NaNs.  Those have been
  replaced with 0.0 in the new inverse LUT.

Nathan Vegdahl requested review from Sergey Sharybin 2023-10-04 19:30:05 +02:00

Nathan Vegdahl requested review from Brecht Van Lommel 2023-10-04 19:30:16 +02:00

Nathan Vegdahl commented

2023-10-04 19:40:04 +02:00

Before	After

| Before | After | |----|----| | ![lights_on_plane_before.jpg](/attachments/8b6e6d4c-d8ab-47bf-95ee-532c9351e10a) | ![lights_on_plane_after.jpg](/attachments/2d0900de-47ef-40da-9a5e-fdba16f97f42) |

lights_on_plane_before.jpg

102 KiB

lights_on_plane_after.jpg

102 KiB

Sergey Sharybin approved these changes 2023-10-05 09:37:28 +02:00

Brecht Van Lommel approved these changes 2023-10-05 18:01:20 +02:00

Nathan Vegdahl merged commit e26d287520 into blender-v4.0-release

2023-10-06 10:12:33 +02:00

Nathan Vegdahl referenced this issue from a commit

2023-10-06 10:12:33 +02:00

Fix #112018: increase AgX LUT resolution

Nathan Vegdahl deleted branch agx_banding_fix

2023-10-06 10:12:38 +02:00

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Fix #112018: increase AgX LUT resolution #113253