Interactive Shader That Reveals Your Fovea’s Footprint

An interactive shader visualizes the fovea by making motion obvious only at the fixation point while the periphery appears mostly static. It uses noise-driven, rotating cross-like strokes layered with color modulation and relies on smoothness to avoid peripheral detection. Scaling for display PPI and fullscreen viewing help maximize the illusion.

Key Points

• Fixate on a point: only a small central region shows clear rotation, revealing the fovea’s high-acuity area; moving your head/distance changes the perceived size.
• Fullscreen and correct scaling improve the illusion; the scale constant is tuned for ~100 PPI and may need tweaking for other displays.
• The effect is built from procedural noise-based, time-rotated, thin cross-like strokes layered with random offsets and sinusoidal color modulation.
• Smooth motion and gentle color/intensity changes are essential; strong, sharp edges are easily detected in peripheral vision and can ruin the effect.
• Other shapes could also work, but the chosen parameters (thickness, length, layers, speed) and smoothness are critical to the perceptual outcome.