To reduce a 3D model for retro games, focus on polycount reduction and texture simplification—retro hardware has limited memory and can’t handle high-polygon or high-resolution assets.
Poly reduction trims unnecessary geometry (e.g., merging redundant vertices, using Blender’s Decimate modifier). Texture simplification means smaller sizes (64x64/128x128) and fewer color channels. Add LOD systems to switch to simpler models for distant objects, and use flat shading instead of complex lighting to lower GPU load.
Use free tools like Blender (poly reduction) or GIMP (texture resizing). Test the model in a retro engine (e.g., Pico-8, Unity with a pixel shader) to ensure it runs smoothly—this matches classic hardware constraints without losing style.