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The problem:

In my application I have a simple Blender scene consisting of:

  • 4 cameras (all parented to a single object)
  • some lights
  • a couple of meshes.

As a rendering engine I use EEVEE and custom materials.

The user of my application needs to move the cameras, change the lights power and record the list of travelled positions while looking at a sufficiently photorealistic real-time rendering of the scene as seen from the 4 cameras.

I created an addon for this, and it kind of works but the Blender interface is too cumbersome to be given to non-expert users.

Therefore I decided to move all the user iteraction to a more intuitive external UI application (written in Python) that communicates to a Blender instance running in background without UI. The communication is already set-up, the only doubt is how to render the 4 viewports in real-time and send the renders to my application.

In other words: if in Blender I move a camera or change a light's power the rendered viewport is updated in real-time. I want to achieve the same feeling, giving some commands from my Python application to the background renderer and receiving back the rendered images within tolerable delay.

My solution so far:

For the communication infrastructure I use GRPC, so no particular delay/overhead should come from this.

At the moment, whenever the user performs any action in the UI an update message is sent to Blender, that triggers a render() command in Blender (actually, 4 render(), one for each camera present in the scene) thus saving the 4 renders in a folder. Once rendering is completed, Blender sends a finished command to the external application that picks up the rendered image files and displays them in the UI

The results:

The proposed architecture works but is too slow to be usable. Even lowering down the resolution of the renderings it takes 3-4 seconds to complete the renderings, so for every update the user has to wait that much time to see the updated rendering, therefore killing the real-time requirement.

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