Warhammer 40,000: Boltgun 2's lead artist reveals how they made pixel art feel authentically retro

Mark Chambers: Pixel art at its best does a lot with very little, which was certainly the case in the times of boomer shooters. Working within those confines resulted in a unique art style, and we captured that look by using crisp, uniformly spaced pixels, showing an authentic, unfiltered version of our sprites but with the added bonus of a bit of modern sharpening and polish.

MC: Considering that shader technology has developed vastly from what it once was, we had to be very careful with how we applied modern techniques. Things like reflection, liquid and transparency are used sparingly so as not to lose the retro feel. 

MC: Warhammer 40k features characters with considerable amounts of detail. One of the challenges we faced when creating enemies for Boltgun 2 was converting things down into a pixel art format while still making them recognisable at lower resolutions.

Step one is sourcing good references. We're in the unique situation of working with an IP that has countless amazing examples of concept art and established designs, so we're able to pick and choose candidates from a wide selection. We look for things like recognisable shapes and strong silhouettes that would read well to players in-game.

Our animation style uses the same ideas of style over realism, and poses and gestures are often exaggerated to sell strong, recognisable silhouettes. We also purposely reduce the number of frames to include only the most important angles, which is also a nice callback to how characters were animated back in the day.

MC: We begin by building 3D models and then the process of pixelisation occurs. We use a custom rendering setup that captures assets from 8 x camera directions, and a script converts the output to a compressed 2d sprite sheet composed of several different materials (spread across a number of channels).

As a final step, our rendered character gets projected onto a billboarding plane for players to marvel and blast away at.

MC: We use Normal and AO maps to reflect surface detail and essentially 'fake' the look of 3d onto 2d sprites (a key component in the look of our game). Glowing emission and reflection masks are available too, and we even have something called an SDF layer that enables cool status effects and overlays where needed.

MC: We use a 'hand-painted' technique to artificially bump values like shadows and lighting (also known as Ambient Occlusion), which helps with the readability of assets in-game. 

A favourite technique is applying edge highlights to really make models 'pop'. Our painting style probably shares a lot in common with how real-world Warhammer 40,000 models are painted (with the added benefit of CTRL Z)

MC: Pixel art is an impressive medium which requires a lot of effort and skill. Nothing says polished retro graphics like nice, crisp pixels being blasted across the screen at an accelerated pace, and there's an appeal to games that lean more into strong visual styles over realism. A world of '3d pixels' gives us that aesthetic, and the concept can be applied to great effect.

MC: We've worked hard to develop a pipeline that captures the idea of a 'polished retro' boomer shooter, especially for characters. There were many challenges involved in the process, from exploring how best to use pixel art in a 3D setting to balancing performance, translating high levels of Warhammer 40,000 detail, and ensuring a consistent look across all areas of the game.

MC: Modern Render engines give us the flexibility to quickly experiment with different pixel resolutions in order to find that sweet spot of consistency, while still looking retro. Back in the day, artists had to ‘bake’ pixels in by hand, ensure everything was balanced, and manually make changes if needed. There's also the massive benefit of being able to capture sprites from 3D models now.