@PaulMelis
Of cause you can’t reproduce it. With Xvfb your machine is not headless. But this im my whole point.
My machine is headless and should be fine rendering CYCLES. But it is not…
If the scene contains grease pencil objects, does require OpenGL for rendering even if they are composited over a Cycles render.
First of all, thank you for your reply.
Okay, so how can we detect all the things that don’t work on headless machines?
Because as I said, I’m coming from a renderfarm and need to stop all unrenderable projects.
Also, for my project I couldn’t find any grease pencil things but I don’t exactly know what to look for.
I wish I were better at Blender and coding 
The term “headless” is a bit overloaded, so what exactly do you mean by that?
- A machine without a GPU
- A machine with a GPU but without a display attached
- A machine with a GPU, but that does not (or cannot) run an X server
Instead of blocking Blender scenes that contain display-related items, why not set up the renderfarm nodes to provide a software OpenGL implementation (i.e. Mesa) and X server? There used to be a blender-softwaregl binary included in the official binaries, precisely for the former purpose, but I don’t know how well it interacts with EEVEE (although I suspect Mesa supports a new enough OpenGL profile).
- A machine with a GPU but without a display attached
That is exactly what I meant
Actually I never heard about an X server. Something I need to research…
Well, our “renderfarm nodes” are other peoples PCs. https://www.sheepit-renderfarm.com/
I’m not sure about things we need to install on their system. But we could put it in our tutorial section.
Right now is Xvfb causing a few problems. EEVEE frames that takes 2 seconds locally takes 4,5 minutes on Colab (on a Nvidia P100)
Looks like there are some issues specifically when rendering with a P100 GPU. And the Radeon RX 580. I’m surprised you even get consistent results over different brands of GPUs, as it will mix CUDA and OpenCL renders in the same animation, where the render implementations differ AFAIK. But I’m no expert in how reproducable Blender GPU renders are anyway over the set of all CPU model + GPU model + GPU drivers + OS + … combinations. It’s certainly not the easiest task do consistent rendering using a set of heterogeneous nodes with GPUs.
That could easily be caused by software OpenGL rendering being used, instead of the hardware-acceleration of the GPU.
That could explain it. (the CPU is pretty weak)
But what would be another option? If Xvfb is only using the CPU, how can I use the GPU?
Another software?
EEVEE is based on the OpenGL API for rendering. The only way to do hardware-accelerated OpenGL rendering of the type that Blender currently needs on an NVIDIA GPU (on Linux) is by having an X server running. There simply is no other way to get the required hardware-accelerated OpenGL context.
The only way to do accelerated OpenGL rendering without an X server (or other windowing system) is through EGL. There are some developments in this area for Blender (e.g. https://developer.blender.org/T54638 and https://developer.blender.org/D6585) but it doesn’t seem production ready yet.
So for EEVEE there currently is no good workaround other than using software-based OpenGL rendering.
2 Likes
Anyway, thank you for your hints 