Viewer node pixels do not update when running blender in background-mode #91891

New Issue

Andrea · 2021-10-01T23:49:05+02:00

Andrea commented

2021-10-01 23:49:05 +02:00

System Information
Operating system: Linux-5.11.0-37-generic-x86_64-with-glibc2.31 64 Bits
Graphics card: Mesa Intel(R) UHD Graphics 630 (CFL GT2) Intel 4.6 (Core Profile) Mesa 21.0.3

Blender Version
Broken: version: 2.93.4, branch: master, commit date: 2021-08-31 09:23, hash: b7205031ce
Worked: (newest version of Blender that worked as expected)

Short description of error
I am trying to render images using blender as a python module. I compiled blender as bpy.so module following the official guide at the following link:

https://wiki.blender.org/wiki/Building_Blender/Other/BlenderAsPyModule

The installation works fine if I save renders to file on the hard disk. What I want to do is access the rendered pixels before they are saved to file because I need to process the image within python. Saving the image to file and reloading it is not feasible due to performance issues. I have been able to use this workaround using the viewer node as described at this link, although only with the blender UI open:

https://ammous88.wordpress.com/2015/01/16/blender-access-render-results-pixels-directly-from-python-2/

When running it using blender compiled as a python module, this doesn't work. Specifically, the viewer node pixels don't seem to get updated (their value is always 0 and the resolution is always default and cannot be changed). I found a similar problem when running blender in the background as described here:

https://blender.stackexchange.com/questions/69230/python-render-script-different-outcome-when-run-in-background/81240#81240

I'm encountering the same issue when running blender as a python module. I tried following the steps at the previous link to rebuild blender and enable background viewer node update but the source code seems to have changed since the time of that post (the steps are shown in the picture below). Is this still possible? I think there is a lot of potential in this feature and it seems it can be activated by simply rebuilding the module from source. If that's the case, it would be nice to know how.

Thanks.

Exact steps for others to reproduce the error
The problem can be reproduced using the file provided (it is simply the default file). The bpy module has been built using the last available source code from the blender repository at the time of writing. The python code to reproduce the problem is:

import bpy
import numpy as np

bpy.ops.wm.open_mainfile(filepath="default.blend")

bpy.context.scene.render.use_compositing = True
bpy.context.scene.use_nodes = True
tree = bpy.context.scene.node_tree
links = tree.links

for n in tree.nodes:
     tree.nodes.remove(n)

rl = tree.nodes.new('CompositorNodeRLayers')      

vl = tree.nodes.new('CompositorNodeViewer')   
vl.use_alpha = True
links.new(rl.outputs[0], vl.inputs[0])  # link Renger Image to Viewer Image
links.new(rl.outputs[2], vl.inputs[1])  # link Render Z to Viewer Alpha

# render
bpy.context.scene.render.resolution_percentage = 100 #make sure scene height and width are ok (edit)
bpy.ops.render.render()

# get the pixels and put them save them to a numpy array
pixels = np.array(bpy.data.images['Viewer Node'].pixels)

print(pixels.sum())

the output of the code is:

Read blend: default.blend
Fra:1 Mem:49.33M (Peak 50.00M) | Time:00:00.09 | Syncing Cube
Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.11 | Syncing Light
Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.11 | Syncing Camera
Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.12 | Rendering 1 / 64 samples
Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.54 | Rendering 26 / 64 samples
Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.81 | Rendering 51 / 64 samples
Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.95 | Rendering 64 / 64 samples
Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing
Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing | Determining resolution
Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing | Initializing execution
Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing | De-initializing execution
0.0

note that the script correctly renders the scene but the output of the print() function returns 0.0 which means that the values in the "pixels" array are all 0.

**System Information** Operating system: Linux-5.11.0-37-generic-x86_64-with-glibc2.31 64 Bits Graphics card: Mesa Intel(R) UHD Graphics 630 (CFL GT2) Intel 4.6 (Core Profile) Mesa 21.0.3 **Blender Version** Broken: version: 2.93.4, branch: master, commit date: 2021-08-31 09:23, hash: `b7205031ce` Worked: (newest version of Blender that worked as expected) **Short description of error** I am trying to render images using blender as a python module. I compiled blender as bpy.so module following the official guide at the following link: https://wiki.blender.org/wiki/Building_Blender/Other/BlenderAsPyModule The installation works fine if I save renders to file on the hard disk. What I want to do is access the rendered pixels before they are saved to file because I need to process the image within python. Saving the image to file and reloading it is not feasible due to performance issues. I have been able to use this workaround using the viewer node as described at this link, although only with the blender UI open: https://ammous88.wordpress.com/2015/01/16/blender-access-render-results-pixels-directly-from-python-2/ When running it using blender compiled as a python module, this doesn't work. Specifically, the viewer node pixels don't seem to get updated (their value is always 0 and the resolution is always default and cannot be changed). I found a similar problem when running blender in the background as described here: https://blender.stackexchange.com/questions/69230/python-render-script-different-outcome-when-run-in-background/81240#81240 I'm encountering the same issue when running blender as a python module. I tried following the steps at the previous link to rebuild blender and enable background viewer node update but the source code seems to have changed since the time of that post (the steps are shown in the picture below). Is this still possible? I think there is a lot of potential in this feature and it seems it can be activated by simply rebuilding the module from source. If that's the case, it would be nice to know how. Thanks. **Exact steps for others to reproduce the error** The problem can be reproduced using the file provided (it is simply the default file). The bpy module has been built using the last available source code from the blender repository at the time of writing. The python code to reproduce the problem is: ``` import bpy import numpy as np bpy.ops.wm.open_mainfile(filepath="default.blend") bpy.context.scene.render.use_compositing = True bpy.context.scene.use_nodes = True tree = bpy.context.scene.node_tree links = tree.links for n in tree.nodes: tree.nodes.remove(n) rl = tree.nodes.new('CompositorNodeRLayers') vl = tree.nodes.new('CompositorNodeViewer') vl.use_alpha = True links.new(rl.outputs[0], vl.inputs[0]) # link Renger Image to Viewer Image links.new(rl.outputs[2], vl.inputs[1]) # link Render Z to Viewer Alpha # render bpy.context.scene.render.resolution_percentage = 100 #make sure scene height and width are ok (edit) bpy.ops.render.render() # get the pixels and put them save them to a numpy array pixels = np.array(bpy.data.images['Viewer Node'].pixels) print(pixels.sum()) ``` the output of the code is: ``` Read blend: default.blend Fra:1 Mem:49.33M (Peak 50.00M) | Time:00:00.09 | Syncing Cube Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.11 | Syncing Light Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.11 | Syncing Camera Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.12 | Rendering 1 / 64 samples Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.54 | Rendering 26 / 64 samples Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.81 | Rendering 51 / 64 samples Fra:1 Mem:49.70M (Peak 50.04M) | Time:00:00.95 | Rendering 64 / 64 samples Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing | Determining resolution Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing | Initializing execution Fra:1 Mem:49.22M (Peak 89.25M) | Time:00:01.00 | Compositing | De-initializing execution 0.0 ``` note that the script correctly renders the scene but the output of the print() function returns 0.0 which means that the values in the "pixels" array are all 0.

Andrea commented

2021-10-01 23:49:05 +02:00

Added subscriber: @Andrea-3

Andrea commented

2021-10-01 23:50:30 +02:00

default.blend

this is the file used to reproduce the results.

[default.blend](https://archive.blender.org/developer/F10723630/default.blend) this is the file used to reproduce the results.

Andrea commented

2021-10-02 02:30:22 +02:00

Removed subscriber: @Andrea-3

Andrea commented

2021-10-02 02:30:24 +02:00

Added subscriber: @Andrea-3

Pete commented

2021-11-13 14:33:59 +01:00

Added subscriber: @Gadgeteering

Pete commented

2021-11-13 14:44:28 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Pete commented

2021-11-13 14:44:28 +01:00

I am having the same problem, it seems that the source code for a couple of the header files need to be updated to solve this issue.

Solution

I am having the same problem, it seems that the source code for a couple of the header files need to be updated to solve this issue. [Solution](https://blender.stackexchange.com/questions/69230/python-render-script-different-outcome-when-run-in-background?answertab=votes#tab-top)

Pratik Borhade commented

2022-03-22 08:06:03 +01:00

Changed status from 'Confirmed' to: 'Needs Triage'

Germano Cavalcante commented

2022-03-22 20:00:02 +01:00

Added subscribers: @lichtwerk, @ideasman42, @mano-wii

Germano Cavalcante commented

2022-03-22 20:00:02 +01:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Germano Cavalcante commented

2022-03-22 20:00:02 +01:00

Blender as a python module is not something the #triaging team is used to checking.

I'm not sure if this is a feature tracked by this Bug Tracker (I didn't even find a tag for it).

@ideasman42, if I'm not mistaken, you're maintaining the module. How would you like these issues to be handled?

(@lichtwerk, I'm tagging you in case I'm missing something).

Blender as a python module is not something the #triaging team is used to checking. I'm not sure if this is a feature tracked by this Bug Tracker (I didn't even find a tag for it). @ideasman42, if I'm not mistaken, you're maintaining the module. How would you like these issues to be handled? --- (@lichtwerk, I'm tagging you in case I'm missing something).

Philipp Oeser commented

2023-02-14 12:31:59 +01:00

If we move this out of the triaging queue (by changing status label to Needs Information from Developers), this needs to be the responsibility of a module (so a Module label must be added)

If we move this out of the triaging queue (by changing status label to `Needs Information from Developers`), this needs to be the responsibility of a module (so a `Module` label must be added)

Philipp Oeser added

Status

Needs Triage

and removed

Status

Needs Info from Developers

labels 2023-02-14 12:32:09 +01:00

Pratik Borhade commented

2023-03-23 05:45:39 +01:00

if I'm not mistaken, you're maintaining the module. How would you like these issues to be handled?

@ideasman42 ^

> if I'm not mistaken, you're maintaining the module. How would you like these issues to be handled? @ideasman42 ^

Campbell Barton commented

2023-03-23 07:48:22 +01:00

This isn't related to running blender as a Python module, the same problem happens in background mode.

Save as test_render.py

import bpy
import numpy as np

bpy.context.scene.render.use_compositing = True
bpy.context.scene.use_nodes = True
tree = bpy.context.scene.node_tree
links = tree.links

for n in tree.nodes:
     tree.nodes.remove(n)

rl = tree.nodes.new('CompositorNodeRLayers')      

vl = tree.nodes.new('CompositorNodeViewer')   
vl.use_alpha = True
links.new(rl.outputs[0], vl.inputs[0])  # link Renger Image to Viewer Image
links.new(rl.outputs[2], vl.inputs[1])  # link Render Z to Viewer Alpha

# render
bpy.context.scene.render.resolution_percentage = 100 #make sure scene height and width are ok (edit)
bpy.ops.render.render()

# get the pixels and put them save them to a numpy array
pixels = np.array(bpy.data.images['Viewer Node'].pixels)

print(pixels.sum())

import sys
sys.exit(0)

Run:

blender --factory-startup --python test_render.py

Now run:

blender --factory-startup --background --python test_render.py

When in background mode, the printed result is 0.0

This isn't related to running blender as a Python module, the same problem happens in background mode. ---- Save as `test_render.py` ```py import bpy import numpy as np bpy.context.scene.render.use_compositing = True bpy.context.scene.use_nodes = True tree = bpy.context.scene.node_tree links = tree.links for n in tree.nodes: tree.nodes.remove(n) rl = tree.nodes.new('CompositorNodeRLayers') vl = tree.nodes.new('CompositorNodeViewer') vl.use_alpha = True links.new(rl.outputs[0], vl.inputs[0]) # link Renger Image to Viewer Image links.new(rl.outputs[2], vl.inputs[1]) # link Render Z to Viewer Alpha # render bpy.context.scene.render.resolution_percentage = 100 #make sure scene height and width are ok (edit) bpy.ops.render.render() # get the pixels and put them save them to a numpy array pixels = np.array(bpy.data.images['Viewer Node'].pixels) print(pixels.sum()) import sys sys.exit(0) ``` Run: `blender --factory-startup --python test_render.py` Now run: `blender --factory-startup --background --python test_render.py` When in background mode, the printed result is `0.0`

👀 1

Campbell Barton changed title from ~~Viewer node pixels do not update when running blender as python module~~ to Viewer node pixels do not update when running blender in background-mode

2023-03-23 07:54:16 +01:00

Germano Cavalcante added

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Viewer node pixels do not update when running blender in background-mode #91891