Exact Projections onto the Hemisphere

Exact Projections onto the Hemisphere Inproceedings

Wolfgang Stürzlinger


Recent approaches to realistic image synthesis have split the rendering process into two passes. The first pass calculates an approximate global illumination solution, the second generates an image of high quality from a given view point using the illumination solution obtained in the first pass.
This paper discusses a new method for projecting polygons onto the hemisphere which is the central operation performed for each pixel during the local pass. The method calculates an exact hemispherical projection of all polygons considering occlusion. The chosen representation of the projected polygons facilitates the fast and accurate computation of formfactors with regard to the projection center.
The new hemispherical projection method is used to obtain an exact local pass solution.

Date of publication: May - 1995
Footnote: Newer work such as "Visibility Silhouettes for Semi-Analytic Spherical Integration", http://dx.doi.org/10.1111/cgf.12257 and "Vectorization for Fast, Analytic, and Differentiable Visibility", https://doi.org/10.1145/3452097 uses the same idea of decomposing projections into convex polygons.
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