Viewport Render Animation - From the Command Line

Question

Inside of the 3D Viewport, there is an option available to perform a 'Viewport Render Animation'. My understanding of this feature is that it performs a full render, using viewport settings across the entire blend file.

Is it possible to invoke this feature directly from the command line? (From either command line arguments or custom python?) I understand it may be possible to look up the individual viewport settings, and set each one in python from the command line, prior to the '-a' argument. But I want the render settings to update as viewport settings change, without updating the render script.

Thanks in advance for all help and consideration.

Answer 1

I did some investigation, and I may be mistaken, but I don't believe this feature is currently possible in Blender 3.1.2.

It's possible to perform a Viewport Render Animation inside of the python console via:

bpy.ops.render.opengl(animation=True)

This will use the context and settings of the viewport in the scripting tab, and will save to the directory defined in Output Properties. However, if you were to run blender from the command line, passing in the following python script:

import bpy
bpy.ops.render.opengl(animation=True)

It will come back with the error:

RuntimeError: Error: Cannot use OpenGL render in background mode (no opengl context)

Line 733 of ~/source/blender/editors/render/render_opengl.cc contains

  if (G.background) {
    BKE_report(
        op->reports, RPT_ERROR, "Cannot use OpenGL render in background mode (no opengl context)");
    return false;
  }

Which leads me to believe this is a hard-coded limitation. Blender is checking whether it is simply running in background mode, with no apparent means of instantiating an opengl context and passing it to the opengl operator. (bContext *C is never checked prior to G.background in that method, so it does not matter what is passed.)