Developer creates real-time 3D shader demo for the Game Boy Color — you can download the ROM or interact with the 3D teapot online

Source: Tom’s Hardware

A canny developer has managed to coax a Game Boy Color (GBC) into running an interactive, user‑controlled, real‑time 3D shader demo. Danny Spencer shared a video, a blog post, downloadable ROMs, source code, and even embedded the demo in an online GBC emulator, so anyone interested can give his Lambert‑shaded 3D teapot a spin.

Image credit: Danny Spencer

While the extra speed is useful for this real‑time 3D demo, the GBC’s processing is still sorely lacking for running a user‑interactive shader. Spencer devotes a significant section of his blog to explaining how the SM83’s lack of a multiply instruction was sidestepped by using logarithms and lookup tables. To reduce computation overhead, he converted vectors to spherical coordinates and implemented the Lambert shader using a spherical dot product. Far more detail about the programming, math, and rendering is available in the linked blog post.

The Game Boy Color’s PCB – Image credit: Evan‑Amos

Download and play with the demo

Spencer has made the gbshader code and related resources available on GitHub. There you will also find links to grab GBC ROM releases for this interactive 3D shader demo.

It is most convenient for the majority of readers to run the shader demo inside the embedded emulator via the blog post. Use the cursor keys to adjust the position of the light source while also manipulating the teapot view angle. On a computer keyboard, both parameters can be adjusted simultaneously to control the animation and lighting.