colour_hdri.sampling.variance_minimization Module

Viriyothai (2009) Variance Minimization Light Probe Sampling

Defines Viriyothai (2009) variance minimization light probe sampling objects:

References

[1]Viriyothai, K., & Debevec, P. (2009). Variance minimization light probe sampling. SIGGRAPH’09: Posters, (Egsr), 60558. doi:10.1145/1599301.1599393
class colour_hdri.sampling.variance_minimization.Light_Specification[source]

Bases: colour_hdri.sampling.variance_minimization.Light_Specification

Defines a light probe sampling resulting light specification.

Parameters:
  • uv (array_like) – \(uv\) coordinates of the sampled light.
  • colour (array_like) – Sampled light colour.
  • index (array_like) – Sampled light location index in its original array.

Create new instance of Light_Specification(uv, colour, index)

colour_hdri.sampling.variance_minimization.luminance_variance(a)[source]

Computes the Luminance variance of given \(a\) 2-D array.

Parameters:a (array_like) – \(a\) 2-D array to compute the Luminance variation.
Returns:\(a\) 2-D array Luminance variance.
Return type:numeric

Examples

>>> a = np.tile(np.arange(5), (5, 1))
>>> luminance_variance(a)  # doctest: +ELLIPSIS
12.2474487...
colour_hdri.sampling.variance_minimization.find_regions_variance_minimization_Viriyothai2009(a, n=4)[source]

Finds the \(2^n\) regions using Viriyothai (2009) variance minimization light probe sampling algorithm on given \(a\) 2-D array.

Parameters:
  • a (array_like) – \(a\) 2-D array to find the regions.
  • n (int) – Iterations count, the total regions count is \(2^n\).
Returns:

Regions with variance minimized.
Return type:

list
colour_hdri.sampling.variance_minimization.highlight_regions_variance_minimization(a, regions, highlight_colour=array([0, 1, 0]))[source]

Highlights regions using with variance minimized on given \(a\) 3-D array.

Parameters:
  • a (array_like) – \(a\) 3-D array to highlight the regions.
  • regions (array_like) – Regions with variance minimized.
  • highlight_colour (array_like) – Highlight colour.
Returns:

\(a\) 3-D array with highlighted regions.
Return type:

ndarray
colour_hdri.sampling.variance_minimization.light_probe_sampling_variance_minimization_Viriyothai2009(light_probe, lights_count=16, colourspace=None)[source]

Sample given light probe to find lights using Viriyothai (2009) variance minimization light probe sampling algorithm.

Parameters:
  • light_probe (array_like) – Array to sample for lights.
  • lights_count (int) – Amount of lights to generate.
  • colourspace (colour.RGB_Colourspace, optional) – RGB colourspace used for internal Luminance computation.
Returns:

list of Light_Specification lights.
Return type:

list