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Sharp Bilinear Filters: Big Clean Pixels for Pixel Art

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Michael Martin

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Sharp Bilinear Filters: Big Clean Pixels for Pixel Art is an October 2025 OpenGL blog post by Michael Martin on Bumbershoot Software about magnifying pixel art without nearest-neighbor shimmer or full bilinear blur.

It derives sharp bilinear filtering: enable GL_LINEAR, then remap coordinates so texel interiors sample the center while only a tunable border blends. It maps a pixel border width into texel space with fwidth, ports OpenGL 3.2 and 2.1 shaders, covers texture-size uniforms and GL_CLAMP_TO_EDGE, and notes rotated sprites still work under fwidth. Cole Cecil and Algorithmic Pensieve articles are cited as prior art.

It is for intermediate OpenGL and pixel-art engine authors who already sample 2D textures. Basic GLSL filter modes are assumed.

The article is a free page with demos, full shader listings, and uniform setup notes.

It is useful when enlarged pixels must stay crisp yet blend cleanly at texel edges on high-DPI displays.