Snake Rewind: Episode 7 - Shine On

In Episode 7 of the Snake Rewind devlog we step into post processing territory and bring our retro grid to life with a glowing bloom shader. Based on LearnOpenGL’s bloom effect tutorial, we implement a multi pass blur system that highlights bright pixels and makes every move feel just a bit more cinematic.

What We Covered

• Implemented a multi pass bloom/glow shader:
  1. Brightness threshold
  2. Horizontal blur
  3. Vertical blur
• Applied additive blending to layer the glow over the original scene
• Used flipped source rectangles to correct Y-axis rendering (Raylib/OpenGL quirk)
• Tuned glow strength with opacity and blur spread

With this effect in place Snake Rewind now looks like an arcade game in a neon dream and the groundwork is laid for more shader polish to come.

Design Insights

• Raylib’s render textures are vertically flipped by default: fix with src.height = -HEIGHT
• Threshold pass helps isolate which pixels should glow (based on luminance)
• Separable Gaussian blur (horizontal + vertical) is performant and visually clean
• Applying Gaussian blur multiple times gives a more defined and spread blur

Implementation Highlights

• Custom threshold.glsl and blur.glsl shaders in GLSL 330
• Multiple RenderTexture2D buffers: target, tmpA, tmpB and blurred
• Ping pong render strategy to apply blur passes cleanly

Why This Matters

Visuals matter and even a simple game like Snake gains impact and atmosphere when it glows in the right places. Our glow shader sets the tone for future effects like scanlines and chromasep.

External Resources

• LearnOpenGL.com: Bloom - our main source for implemetation of bloom/glow shader

What’s Next?

In Episode 8 we’ll dial in the retro feel even further with animated scanlines giving our game the look of a vintage CRT arcade screen.