UX - Building the CLAW Render Pipeline for Blender

Introduction

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Ask ten different people what user experience means, and you’ll probably get ten different answers. For some, it’s all about clean interfaces and intuitive design. Others might focus on performance, making sure everything loads quickly and works seamlessly. And for developers, UX can mean efficiency—cutting down on repetitive tasks and streamlining workflows so they can focus on the creative work that really matters.

One crucial, often overlooked part of UX is the experience of developers building tools and managing workflows. As a UX designer who also happens to be a developer, I’ve had to wrestle with repetitive tasks, especially when working with 3D animations or sprite sheets.

This project is an evolutionary off-shoot of a previous project I worked on called JunkerPunk. I’ve set up a PaperZD sprite character using an 8-sided billboarding technique, where the image and sprite rotation dynamically updates relative to the camera angle—a hybrid between the classic look of Doom and the more modern, stylized aesthetic of Octopath Traveller but you can rotate around your character freely in a 3d environment and have each sprite update automatically based on the angle, basically.

Each animation for this character has to be rendered in 3D with a custom pixel art shader, converted into 2D textures, and then imported into Unreal Engine. Managing this manual process across multiple angles was time-consuming, which led me to develop the CLAW (Camera Loop Animation Workflow) to streamline and automate the entire workflow.

CLAW is a (tested and working as of Blender version 2.4.1 and Unreal Engine version 5.4.4) simple isometric render pipeline built in Python. This tool has transformed my workflow, cutting the time I spend rendering and processing animations from 45 minutes per animation to just 2-4 minutes. I’m really happy with the direction I’ve been able to take it so far for my Unreal development work so maybe it can help you too or get you pointed in the right direction at least. 🙂

Let me walk you through how I got there and why optimizing developer experience is just as important as any other part of UX.

The Old Workflow: 45 Minutes of Repetition

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Before I built CLAW, my workflow for rendering animations from Blender to Unreal Engine was incredibly tedious. Here’s what it looked like:

1. Render 8 Sides of a Character in Blender:
   I would render out 8 different angles of a character performing an animation, using 8 static cameras, each producing individual PNG frames.

2. Convert the PNG Frames into a Sprite Sheet:
   Next, I would use a command called Montage (available on Homebrew) to stitch the frames into a sprite sheet. If you’re curious, here’s the command I ran:

   montage * -geometry 512x512 -tile 6x6 -background transparent -filter Catrom spritesheet.png
   

   I found the Catrom filter to be the best filter for my custom pixel art shader in Blender. This command creates a sprite sheet with 6 columns and 6 rows, where each image is sized to 512x512 pixels. You’ll have to estimate the rows based on your number of total images. Of course, this can be adjusted based on your needs, these just worked for what I needed.

3. Import the Sprite Sheets to Unreal Engine:
   After creating sprite sheets for each angle, I would import them into Unreal Engine, slice them up manually, convert them into flipbooks, and set up an AnimationSequence in PaperZD using those flipbooks.

4. Wire It All Up:
   Finally, I’d wire everything up as an AnimationSource in the PaperZD graph to make sure the character’s animations ran properly in the engine.

This process took 45 minutes per animation, depending on the complexity. It felt like an eternity, especially when small tweaks were needed, and you can forget things like doing this several times if you want height maps, damaged or alternate versions of a sprite, etc. You could probably spend days just manually generating images. Ouch.

The CLAW Pipeline: 2-4 Minutes with One Click

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Now, let’s talk about how CLAW changed everything. Here’s how I cut that workflow down to 2-4 minutes, with a single click with this pipeline.

Blender Script: Automating PNG Exports

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The first script from my repo under ./Blender runs in Blender 🤪. Just copy + paste and save it to your Scripting tab, adjust it to the location you want to save and update the cameras with your scene camera names and run it. The default configuration automatically exports PNG frames for 8 different angles of a character’s animation into the appropriate folder structure:

{character_name}/{Action_name}/{Direction}/SpriteSheet.png

The script can handle as many angles as you need—just create the cameras in Blender, position them, name them, and reference them in the script.

ImageMagick: Creating the Sprite Sheets

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Once the raw PNG frames are exported, the script then uses ImageMagick to combine those images into a sprite sheet. This sprite sheet is automatically saved to the same folder as the PNG frames.

This part of the pipeline is standalone, meaning you can use it outside of Unreal with something like Unity or Godot, etc if you don’t need the full integration. To run it, you’ll need to manually designate:

• The output path for the sprite sheets
• The character’s name
• The animation’s name
• The location of Montage (I just installed it using Homebrew so default value is where it was for me)

You can determine the location if you are on Mac/Linux if you go into terminal and type ‘which montage’.

Unreal Engine Script: Automating Sprite Slicing and Flipbook Creation

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The second script runs inside Unreal Engine and does the next steps:

• Slicing the sprite sheet into individual frames using ImageMagick. Unfortunately, Unreal doesn’t currently support Python integration for sprite extract method’s grid-based sprite sheet slicing natively—or if it does, it’s eluded me! So, we’re making them individually to work around that with ImageMagick.
• Applying Paper2D texture settings and setting the Nearest image filter for the best pixel art results.
• Sorting the frames into sequential order, identifying empty frames, and combining the remaining ones into a Flipbook.
• Naming the flipbook in the format:
  {action_name}-{Direction}-{character_name}

Once you have the flipbooks, they can be used to create ActionSequences and set up PaperZD Animation States.

Speed Results: From 45 Minutes to 2-4 Minutes

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This entire process now takes between 2-4 minutes depending on the complexity of the animation and how much work ImageMagick needs to do in sorting and deleting empty frames. I tested this with an average animation frame rate of around 30 FPS.

The automation doesn’t just make the work faster; it dramatically reduces the possibility of typos and formatting mismatches. And that’s the heart of a great UX—the less you have to repeat yourself, the more you can focus on what you care about. 😀

Future Features: Automating Action Sequences and Animation States

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While CLAW is already saving me tons of time, the ultimate goal is to take it further. I’m working on making the tool capable of creating ActionSequences and Animation States in Unreal Engine automatically based off of your flipbooks.

This has proven tricky because some elements in PaperZD aren’t normally exposed through Unreal’s python scripting API, but I’m exploring new approaches to make this happen. The pipeline is evolving based on what I learn and what new challenges arise.

Conclusion: Optimizing Developer Experience is UX Too

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Given my background of doing things like this for a living at some places, creating a UX tool like CLAW for my own needs has me ruminating a bit on how we approach UX—not just for end users but for ourselves as Developers, Artists, and Product People. Reducing friction in your workflow can make a world of difference, helping you focus on the creative and fun parts of the job, and automate the repetitive grunt work away.

So if you’re in a similar situation, spending countless hours on rendering and importing animations, think about ways to automate your pipeline. Time is always the one thing we cannot get more of in life.

Happy animating!

Check it out on my GitHub:
If you’re interested in seeing more of CLAW or collaborating on future updates, you can find the project on my GitHub.

Planned Enhancements:

• Automating the creation of ActionSequences and PaperZD Animation States.
• Export heightmaps as separate sprite sheet