Fill Rate
How many pixels the GPU can shade per second
Also known as: Fillrate · Pixel fill rate · Fill rate bound · Overdraw fill rate · Mobile fill rate
Definition
Fill rate is the number of pixels a GPU can shade and write per second, and a game is fill-rate bound when the total pixel work is the limit. Every pixel costs more with a higher resolution, expensive shaders, many lights and layers of transparency drawn on top of each other, which is overdraw. Fill rate is especially limited on mobile and standalone VR devices, where large transparent particles and full-screen effects can quickly use up the budget.
In production
To reduce fill-rate cost, lower the render resolution, simplify pixel shaders, cut the number and size of overlapping translucent surfaces, and use cheaper effects for particles. Tight meshes for cutout textures, called cards trimmed to the shape, avoid shading transparent pixels. Check the shader complexity and overdraw views in your engine to see where the pixel cost is.
Tools that use Fill Rate
See also
Overdraw
Redrawing same pixels
Shader Complexity
Viewport view of per-pixel material cost
Blend Mode
How a material combines with what is behind it
Mobile Optimization
Art budgets for phones and tablets
VR Performance Budget
Why VR needs higher frame rates and simpler art
CPU Bound vs GPU Bound
Which processor limits the frame rate
Particle Effects Too Expensive
An effect eats the frame time