Unbiased rendering

Unbiased rendering in computer graphics refers to techniques that avoid systematic errors, or biases, in the radiance approximation of an image.

The errors in an image produced by unbiased rendering are due to random statistical variance, which appears as high-frequency noise.

[2] Consequently, four times as much data is required to halve the standard deviation of the error, making unbiased rendering less suitable for real-time or interactive applications.

A biased rendering method can still produce images close to the desired result but introduces a certain amount of error (often seen as a blur) to reduce variance (noise).

[4] On the other hand, progressive photon mapping (PPM), a biased technique, handles caustics effectively.