Color handling in OSL shaders¶
Octane is a spectral renderer, so it handles the color variable type in a non-standard way.
Spectrum and RGB¶
Depending on which function returned a given color value, a color variable may be represented
internally as RGB or as a spectral color. When expressions use both RGB colors and spectral colors,
the RGB colors will be converted to spectral colors.
1 2 3 4 5 6 7 8 9 10 11 12 | // a will be an RGB color color a = 1; // b will be an RGB color color b = {1, 0.5, 0}; // c will be a spectral color color c = _gaussian(1, 0.1); // adding two RGB colors results in another RGB color color d = a + b; // adding a spectral color to another color always results in // a spectral color color e = a + c; |
In practice, most colors will end up being represented as RGB colors. The main exceptions are blackbody and Gaussian spectra.
For input variables the representation is determined by the node connected to the corresponding input pin.
RGB colors support element access (using []) and casting to point-like types. For spectral colors
this can be done only approximately, and the result will have poor color fidelity. The compiler will
emit a warning if this happens.
1 2 3 4 | // f1 will contain 0.5 as expected float f1 = b[1]; // the value of v1 will depend on the wavelength sampling. vector v1 = (vector) c; |