How to create a masked image using blender python scripting in blender

Question

I am a beginner at blender. I have 5 cylinders present on the field in the shape of a plane, like this one:

I have 100 images in which the cylinder's shape and position are randomized. I want to create masked images for these 100 images. How can I do it?

I want to make the cylinders black and the field white. I need the script for this. I use Blender 3.6. I don't know which version is the most stable.

Crantisz · Accepted Answer · 2023-07-18 08:07:48Z

No scripting is required.

Cycles

First set pass index for plane and cylinders. Let say field will be 1, cylinders will be 2:

On view layer tab enable Object index:

In compositor window enable use nodes:

Use ID mask node to get right mask (note 0 is background, 1 and 2 the objects that we just assigned):

You can save mask from image editor, or use file output node to save file automatically then the scene is rendered

For EEVEE you can use cryptomatte pass instead. Enable cryptomatte pass in Layer tab:

Then in compositor window pass pick output of cryptomatte node in viewer (you have to enable backdrop feature to have picture at background):

Then click "+" icon and pick on plane (name of the object will be added)

Then you can use mate output to save as mask