Creating Nebula Skyboxes in Blender: Hardware Setup for Rendering

Introduction

Tim Barton: By day, I'm a structural engineer, now fully licensed and practicing. By night, I create artwork with a strict focus on space nebula and planets, but mostly nebula. Really, I'm pretty bad at all other subjects. If you ask me to paint a portrait we're both gonna have a bad time.

Why Blender?

Painting nebula by hand is great, but it can be very difficult to get a sense of depth to the artwork. It takes a lot of iteration and effort to get things to look 3D. Also, it takes many hours of hand painting to get the level of detail that's needed for my clients. Years ago the nebula in Eve Online really caught my eye and I wanted to be able to recreate that amazing sense of depth, while also cutting down the amount of hand detailing.

These were done in Houdini, which requires a major investment of money and training to get started. Blender seemed like an obvious alternative given that it was free. After I saw Gleb Alexandrov's 3D Nebula talk at Blender Conference 2019 I was convinced Blender was good enough to commit my time to.

Hardware for Rendering High-Resolution Skyboxes

First, I put into practice everything that Gleb talks about in his presentation and scoured his Twitter feed for any .blend samples I could find. He really covers most of the techniques that I use if you watch closely. I started with the Eevee render engine within Blender but gave it up because of a lack of quality. I moved to Cycles but the big drawback was how awfully slow it was. A couple of the techniques are:

• Use E-Cycles Nebula build of Blender 2.82
• Render at a lower resolution and upscale with Topaz Gigapixel AI
• Use the Optical Flow algorithm in Davinci Resolve so we can render 1/2 the frames
• Render at low samples for most of the image, then rerender select points of interest at high quality, and patch them in.
• Create your own GPU render farm!

Notice the two new hybrid cards which have an AIO liquid cooler with a radiator.

So I tripled my render speed, but I needed to go faster.  Professional GPU rendering machines are extremely expensive because they assume that the GPUs must use a PCIe x16 slot on the motherboard.

I had a theory that I could use a cryptocurrency mining rig. I bought a used one that had 6 GTX 1060s. It worked pretty well! Using PCIe x1 risers is perfectly acceptable for these scenes because they have almost no geometry and no textures. Today, I have 4 machines in total and an electricity bill as high as some people's rent.

My current hardware (simplifying somewhat) is 12 RTX 2080s across 4 computers which use about 3000 KW-Hr per month (the net at the bottom is to keep the cat away):

I use B-Renderon to do command line rendering on all my machines.

With this, I can render a 16384x8192 skybox in about 5 hours, or about 0.5 seconds of 1080p animation per hour.

One unexpected challenge is dealing with the heat that these GPUs produce. Often, my entire apartment's air conditioning can not keep up once the weather gets really hot.  I live in Texas, you know.

Ultimately, I will upgrade to Nvidia's 3000 series graphics cards for the superior performance/Watt.  For now, they remain out of stock everywhere.

Skybox Production

The clouds are Blender volumes with a 3D procedural noise texture controlling the density of the volume. Getting the noise to look good is 80% of the work. Light sources are just point lights placed by hand. I set up an equirectangular camera, set the resolution, and render. I do get crashes sometimes when Blender is trying to save.  I believe it's a lack of RAM. 32 Gigabytes of RAM is apparently not enough when dealing with 16384x8192 resolution renders in Blender. Now I'll render at about 66% of that, then upscale with Topaz Gigapixel AI. Then I rerender certain points of interest at extremely high quality and resolution and layer them on top in Photoshop.

I'd say the only real challenge with these skyboxes is the RAM issue.  I've got more on the way from Newegg as we speak.  Animation rendering is far more challenging so creating skyboxes has been a pleasant experience.

Tim Barton, Space Art Specialist

Interview conducted by Arti Sergeev