Coherent Path Tracing

Iman Sadeghi1, Bin Chen1, Henrik Wann Jensen1

1UC San Diego

Journal of Graphics, GPU, and Game Tools 14(2)

Coherent Path Tracing

Abstract:

Packet tracing is a popular and ecient method for accelerating ray tracing. However, packet traversal techniques become ineffcient when they are applied to path tracing since the secondary rays are incoherent. In this paper, we present a simple technique for improving the coherency of secondary rays. This technique uses the same sequence of random numbers for generating secondary rays for all the pixels in each sample. This improves the effciency of the packet tracing algorithm, but creates structured noise patterns in the image. We propose an interleaved sampling scheme that reduces the correlation in the noise and makes it virtually imperceptible in the final image. Coherent path tracing is unbiased, simple to implement and outperforms standard path tracing with packet tracing, while producing images with similar RMS error values.
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Text Reference:

Iman Sadeghi, Bin Chen, Henrik Wann Jensen. A practical microcylinder appearance model for cloth rendering. Journal of Graphics, GPU, and Game Tools, 14(2):33-43.
BibTex Reference:

@article{sadeghi2009cpt,
	title = {Coherent Path Tracing},
	author = {Sadeghi, Iman and Chen, Bin and Henrik Wann Jensen},
	year = {2009},
	journal = {Journal of Graphics, GPU, and Game Tools},
	volume = {14},
	number = {2},
	pages = {33-43},
}