Spectral rendering, part 1: Spectra
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Christoph Peters
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Spectral rendering, part 1: Spectra is a November 2025 Moments in Graphics article by Christoph Peters opening a series on implementing spectral rendering in a real-time path tracer.
It contrasts RGB component-wise color math with wavelength-dependent illuminant and reflectance spectra, CIE XYZ matching, and display conversion. Topics include EU energy-label and LSPDD illuminant data, the storage cost of per-texel spectra, spectral upsampling from sRGB via Fourier sRGB and Lagrange multipliers, energy-conserving reflectance evaluation, and why storing multipliers directly is costly. Later parts and a downloadable spectral path tracer are previewed.
It is for intermediate to advanced graphics programmers who know path tracing and color basics. Prior radiometry posts help but the series is written to stand alone.
Access is a free long-form HTML tutorial with equations, figures, references, and companion code and data downloads.
It is useful when moving an RGB renderer toward spectral data without assuming offline-only spectral pipelines.
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