25 screen door transparency issues transparent object

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Unformatted text preview: t holes in it ○ like a screen door ● Using a stipple pattern (like a checkboard pattern) ● The ratio of blocked pixels equal to alpha ● No need of sorting : objects can be drawn in any order ● Z-buffer can handle the overlaps of translucent surfaces alpha = 0.25 Screen-door Transparency: Issues •Transparent object over another transparent object can block everything behind –When fixed patterns are used Screen-door Transparency: Issues 2 •Stipple patterns must be set in the screen space – otherwise suffer from aliasing –Why? –See this http://www.youtube.com/watch?v=gMsmJfiApCs Stochastic Transparency •Multi-sampling : subpixels are produced and the pixel colour is computed by averaging their colour •Random sub-pixel stipple pattern Stochastic Transparency •No sorting needed •The final color of the pixel is computed by averaging those of the subpixels References for hidden surface removal •Foley et al. Chapter 15, all of it. •Introductory text, Chapter 13, all of it •Or equivalents in other texts, look out for: –(as well as the topics covered today) –Depth sort – Newell, Newell & Sancha –Scan-line algorithms •S. Chen and D. Gordon. “Front-to-Back Display of BSP Trees.” IEEE Computer Graphics & Algorithms, pp 79–85. September 1991. http://research.nvidia.com/publication/stochastictransparency *...
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