Shadowing dynamic volumetric media

摘要

A dynamic volumetric medium, such as hair, fog, or smoke, may be represented, for purposes of shadow mapping, by transmittance versus depth data for that medium. In one embodiment, the representation may take the form of a plot of transmittance versus depth, with nodes where the transmittance changes non-live linearly with respect of depth into the medium. The number of nodes in the representation may be reduced to reduce memory footprint and to enable the storage of the representation on the same chip doing the shadow mapping. In some embodiments, the number of nodes may be reduced, one node at a time, by removing the node whose underlying trapezoid has the least area of all the remaining nodes.

主权项

1. A computerized method comprising:
recording entry and exit points of a light ray to define a segment; recording density along segment; integrating transmittance over the segment; compositing integrated transmittance with transmittance values; shadow mapping a dynamic volumetric medium by reducing a number of nodes in a representation of transmittance as a function of depth for that medium by selecting nodes to remove using a computer; identifying intermediate nodes, wherein said intermediate nodes being positioned along said segment intermediate between the beginning and end of the segment; removing intermediate nodes one at a time by selecting in each iteration the intermediate node having a triangle under the intermediate node with the least area of all the remaining intermediate nodes, wherein the triangle of the intermediate node is constructed by the nearest two connected nodes of the intermediate node; and continuing to eliminate nodes until the number of nodes is below the threshold, wherein the threshold is less than the maximum number of nodes.