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# Simple Way to Generate Unusual Specular Reflections

IP.com Disclosure Number: IPCOM000101328D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 57K

IBM

## Related People

Woodwark, JR: AUTHOR

## Abstract

Outlined is a simple way of generating enhanced surface effects when modelling solid geometry with a computer graphic display.

This text was extracted from an ASCII text file.
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Simple Way to Generate Unusual Specular Reflections

Outlined is a simple way of generating enhanced surface
effects when modelling solid geometry with a computer graphic
display.

Standard techniques to achieve surface effects in depicting
three-dimensional scenes include coloured and directional lighting,
reflections and shadows, 2D and 3D texture, and 'bump mapping'.  All
of these are costly in computer time.  This method is inexpensive and
gives the user flexibility to experiment by varying a single
parameter, offset to r.

Suppose that, at a given point on an object, the surface normal
is N, light is arriving along vector L, and the direction to the
viewer is V, as shown in the figure. Assuming that these are unit
vectors, the intensity of Lambert's law lighting is calculated as
L.N.  The intensity of specular reflection is a function of the angle
between the reflection of L and V.  The specular reflection is
typically approximated by a function like
cosn r,
where r = cos-1((L - 2(L.N)N)).V).
The angle r is never explicitly calculated of course.
The proposed modification is to calculate the angle
V - L
r = cos-1([[[[.N)
V - L
but then to subtract from it an angle r chosen from between 0o and 90
degrees, before calculating the specular lighting component, which,
using the simple co...