Compositor scale offset #42844

New Issue

Mikhail Rachinskiy · 2014-12-08T21:35:27+01:00

Mikhail Rachinskiy commented

2014-12-08 21:35:27 +01:00

System Information
Windows 8.1 x64
Renderer: GeForce GTX 860M/PCIe/SSE2

Blender Version
Broken: 2.72.2 c8995ec

Short description of error
There is a little offset when upscaling render in compositor.

Exact steps for others to reproduce the error

Open blend file scale_offset.blend
Press render
Choose Bicubic or Bilinear filter in Transform node and see how image is offsetting a little bit to the down-left
Also choose back to Nearest filter and unmute Pixelate node, which is triggers offset too

**System Information** Windows 8.1 x64 Renderer: GeForce GTX 860M/PCIe/SSE2 **Blender Version** Broken: 2.72.2 c8995ec **Short description of error** There is a little offset when upscaling render in compositor. **Exact steps for others to reproduce the error** - Open blend file [scale_offset.blend](https://archive.blender.org/developer/F130359/scale_offset.blend) - Press render - Choose Bicubic or Bilinear filter in Transform node and see how image is offsetting a little bit to the down-left - Also choose back to Nearest filter and unmute Pixelate node, which is triggers offset too

Mikhail Rachinskiy commented

2014-12-08 21:35:27 +01:00

Changed status to: 'Open'

Mikhail Rachinskiy commented

2014-12-08 21:35:27 +01:00

Added subscriber: @MikhailRachinskiy

Sergey Sharybin self-assigned this 2014-12-09 11:15:18 +01:00

Sergey Sharybin commented

2014-12-09 11:15:18 +01:00

As for the scale issue it seems to be an inconsistency in assumption where the pixel center is (whether it's coordinate (0,0) or (0.5, 0.5) ). What's even worse, those assumptions seems to be different in different areas of compositor. Would need to carefully look over all of the nodes there..

As for pixelate node, i'm not sure how to prevent offset with it's current implementation -- it's just rounds the coordinates to integer values. That would always give some offset... Personally i'd just get rid of such an obscure node..

As for the scale issue it seems to be an inconsistency in assumption where the pixel center is (whether it's coordinate (0,0) or (0.5, 0.5) ). What's even worse, those assumptions seems to be different in different areas of compositor. Would need to carefully look over all of the nodes there.. As for pixelate node, i'm not sure how to prevent offset with it's current implementation -- it's just rounds the coordinates to integer values. That would always give some offset... Personally i'd just get rid of such an obscure node..

Mikhail Rachinskiy commented

2014-12-09 12:48:41 +01:00

Pixelate node is useful when you need to convert hi pix images to low pix, like on this screenshot:

Transform node seems to be more useless, because it duplicates functionality of Scale, Rotate and Translate nodes, but missing valuable options:

Pixelate node is useful when you need to convert hi pix images to low pix, like on this screenshot: ![pixelate.png](https://archive.blender.org/developer/F130444/pixelate.png) Transform node seems to be more useless, because it duplicates functionality of Scale, Rotate and Translate nodes, but missing valuable options: ![trfrm.png](https://archive.blender.org/developer/F130452/trfrm.png)

blender-admin commented

2015-01-20 11:02:35 +01:00

This issue was referenced by 02fad7dca4

This issue was referenced by 02fad7dca4adc5e248440c98293cdf713f25d39d

Sergey Sharybin commented

2015-01-20 11:04:30 +01:00

I know pixelate could be handy, but it's implementation is not offset-proof and it's not totally clear how to avoid it with the current sampling design in compositor.

Fix for interpolation offset will go to git now.

I know pixelate could be handy, but it's implementation is not offset-proof and it's not totally clear how to avoid it with the current sampling design in compositor. Fix for interpolation offset will go to git now.

Sergey Sharybin commented

2015-01-20 11:07:07 +01:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2015-01-20 11:07:07 +01:00

Sergey Sharybin commented

2015-01-20 11:07:07 +01:00

Closed by commit 02fad7dca4.

Closed by commit 02fad7dca4.

blender-admin commented

2015-03-09 08:48:42 +01:00

This issue was referenced by 2ae0f1e70b

This issue was referenced by 2ae0f1e70be543b37f426dc1b7d8a44b05301faf

Sergey Sharybin commented

2015-03-09 08:50:09 +01:00

Changed status from 'Resolved' to: 'Open'

Sergey Sharybin reopened this issue

2015-03-09 08:50:09 +01:00

Sergey Sharybin commented

2015-03-09 08:50:09 +01:00

Re-opening the issue, initial approach was wrong and the actual root of the issue is not just because of the interpolation, but more about how resolution is mapped.

Aaron Carlisle commented

2015-05-10 00:01:43 +02:00

Added subscriber: @Blendify

Jeroen Bakker commented

2015-05-18 23:11:07 +02:00

Added subscriber: @Jeroen-Bakker

Jeroen Bakker commented

2015-05-18 23:11:07 +02:00

In BLI the nearest function is implemented as a float to int conversion
In the COM_MemoryBuffer nearest is implemented as float to int conversion.
In the pixelate it is implemented as a mathematic round. reason for this is to have all pixels the same size in the output.

Yes there is an issue based on the image width/height. Sometimes when translating images you will see rounding issues last/first column missing.
Should be investigated.

In BLI the nearest function is implemented as a float to int conversion In the COM_MemoryBuffer nearest is implemented as float to int conversion. In the pixelate it is implemented as a mathematic round. reason for this is to have all pixels the same size in the output. Yes there is an issue based on the image width/height. Sometimes when translating images you will see rounding issues last/first column missing. Should be investigated.

Monique Dewanchand commented

2015-05-19 21:28:55 +02:00

Added subscriber: @monique

Sergey Sharybin commented

2016-04-26 14:57:18 +02:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2016-04-26 14:57:18 +02:00

Sergey Sharybin commented

2016-04-26 14:57:18 +02:00

Think at this point it's safe to consider this a TODO and something to be addressed with rest of sampling issues when re-considering the whole compositor.

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Compositor scale offset #42844