Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!sdd.hp.com!elroy.jpl.nasa.gov!ames!vsi1!zorch!xanthian From: xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) Newsgroups: comp.graphics Subject: Re: Oh, yeah? well Phong this! Message-ID: <1990Jul13.090115.12814@zorch.SF-Bay.ORG> Date: 13 Jul 90 09:01:15 GMT References: <7834@ccncsu.ColoState.EDU> Distribution: usa Organization: SF Bay Public-Access Unix Lines: 52 In article <7834@ccncsu.ColoState.EDU> mm459504@longs.LANCE.ColoState.Edu (Michael Miller) writes: > >I have heard of several techniques used in 3d modelling, two of which are >Phong a Gouraud shading, but I haven't seen anything that lists their specifics >(i.e. what they do) if anyone can point me in the correct general direction, I >would be very much appreciative. A very nice book for finding out what computer graphics concepts mean, without drowning in the math, but _with_ the vector diagrams, is Andrew Glassner's 3D Computer Graphics, A User's Guide for Artists and Designers, ISBN 0-8306-1003-0. On pages 79 to 83, he distinguishes three shading techniques for an object comprised of a polygonal tiling. Lambert (Faceted) Shading: find the appropriate shade for the surface normal for each polygon, and assign that shade to each pixel of the entire polygon. This give a faceted appearance. Gouraud (Smooth) Shading: for each vertex of the polygon, average the surface normals for all the polygons meeting at that vertex, and assign the shade appropriate to that averaged normal to the vertex. Then shade the polygon by blending the _colors_ from vertex to vertex at each pixel of the polygon. This provides a smooth appearance, but suffers from "Mach banding" artifacts and unrealistic looking highlights sometimes. Phong (Normal Interpolating) Shading: using the same averaged normals for each vertex used by the Gouraud Shading, blend the _normals_ from vertex to vertex, and compute the appropriate shade for each pixel based on the normal computed for that pixel. This gives better highlights and avoids Mach bands, but is much slower to compute. Now, can somebody describe the improvement that "Blinn Shading" added to Phong's work, in equally simple language? Thanks. Kent, the man from xanth. -- ... and don't worry about your deposits; they're insured to the HILT by Republic Savings and Loan of Lubbock, Texas -- Garrison Keillor, American Radio Company of the Air, Season Finale, "Prairie Home Companion Fourth Annual Revival", 16 June 1990.