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Problem with "Point" light sources in Mathematica 7.01

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  Problem with "Point" light sources in Mathematica 7.01 Alexey <lehin.p@gmail.com> - 2011-04-30 09:53 +0000

#1931 — Problem with "Point" light sources in Mathematica 7.01

Hello,

I tried to reproduce the default styling of Plot3D of Mathematica 5 in
Mathematica 7.01 and faced unexpected seemingly wrong behavior of "Point"
light sources in version 7.

Consider the following:

v5Style = {{"Ambient", GrayLevel[0]}, {"Point", RGBColor[{1, 0., 0.}],
    ImageScaled[{2, 0, 2}]}, {"Point", RGBColor[{0., 1, 0.}],
    ImageScaled[{2, 2, 2}]}, {"Point", RGBColor[{0., 0., 1}],
    ImageScaled[{0, 2, 2}]}};
Plot3D[Sin[x y], {x, 0, Pi}, {y, 0, Pi}, Lighting -> v5Style, Mesh ->
20]

The plot generated by the above code is too dark. And the surface colors
does not change when rotating the plot. It means that the "Point" light
sources are fixed in the coordinate system and rotate with the plot.

With "Directional" light sources the problem disappears but it is not the
default lighting style of Mathematica 5:

new = {{"Ambient", GrayLevel[0]}, {"Directional",
    RGBColor[{1, 0., 0.}], ImageScaled[{2, 0, 2}]}, {"Directional",
    RGBColor[{0., 1, 0.}], ImageScaled[{2, 2, 2}]}, {"Directional",
    RGBColor[{0., 0., 1}], ImageScaled[{0, 2, 2}]}};
Plot3D[Sin[x y], {x, 0, Pi}, {y, 0, Pi}, Lighting -> new, Mesh -> 20]

It seems that in the case of "Point" light sources we get wrong  light
directions. Is there a way to avoid this?

Alexey

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