The Shadow Mask Sweep family of shadow algorithms

Conference · Tue Jan 13 04:00:00 EST 1987

OSTI ID:6566300

Grant, C W

The Shadow Mask Sweep (SMS) family of algorithms is a new image synthesis technique for generating shadows. The SMS technique is based on the painter's algorithm for visible surface determination. The antialiased version of the painter's algorithm is based on antialiased digital raster compositing techniques. These compositing techniques have previously assumed that the edges of the objects represented in the rasters were uncorrelated. This causes problems compositing objects modeled with primitives with correlated edges. These objects are common in image synthesis, such as meshes of polygons. It was desired to produce a shadow algorithm that could handle both primitives with correlated and uncorrelated edges in the same image. To do this it was necessary to develop new compositing techniques. A new technique for correlated edges is combined with an extension of the existing uncorrelated edge technique producing a system that can use both. The painter's algorithm is extended to correct operation with both types of primitives using these new compositing techniques. Applying the painter's algorithm simultaneously to both visible surface and shadow determination yields the SMS technique. Algorithms based on the SMS technique are suitable for all opaque ''sharp edged'' primitives than can be rendered with the painter's algorithm and all opaque or transparent ''fuzzy'' primitives that can be rendered with the painter's algorithm. Primitives and combinations of primitives which previously had no efficient, general shadow algorithms, such as particle systems and nonuniform density translucent volumes can now be rendered efficiently using the SMS technique.

• Research Organization: California Univ., Davis (USA); Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6566300
• Report Number(s): UCRL-95948; CONF-870738-1; ON: DE87007054
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
990200* -- Mathematics & Computers
ALGORITHMS
COMPUTER GRAPHICS
IMAGE PROCESSING
IMAGES
MATHEMATICAL LOGIC
PROCESSING
SHADING