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# functions in pl3d.i - l

 light3 ``` light3, ambient=a_level, diffuse=d_level, specular=s_level, spower=n, sdir=xyz Sets lighting properties for 3D shading effects. A surface will be shaded according to its to its orientation relative to the viewing direction. The ambient level A_LEVEL is a light level (arbitrary units) that is added to every surface independent of its orientation. The diffuse level D_LEVEL is a light level which is proportional to cos(theta), where theta is the angle between the surface normal and the viewing direction, so that surfaces directly facing the viewer are bright, while surfaces viewed edge on are unlit (and surfaces facing away, if drawn, are shaded as if they faced the viewer). The specular level S_LEVEL is a light level proportional to a high power spower=N of 1+cos(alpha), where alpha is the angle between the specular reflection angle and the viewing direction. The light source for the calculation of alpha lies in the direction XYZ (a 3 element vector) in the viewer's coordinate system at infinite distance. You can have ns light sources by making S_LEVEL, N, and XYZ (or any combination) be vectors of length ns (3-by-ns in the case of XYZ). (See source code for specular_hook function definition if powers of 1+cos(alpha) aren't good enough for you.) With no arguments, return to the default lighting. EXAMPLES: light3, diffuse=.1, specular=1., sdir=[0,0,-1] (dramatic "tail lighting" effect) light3, diffuse=.5, specular=1., sdir=[1,.5,1] (classic "over your right shoulder" lighting) light3, ambient=.1,diffuse=.1,specular=1., sdir=[[0,0,-1],[1,.5,1]],spower=[4,2] (two light sources combining previous effects) interpreted function, defined at i/pl3d.i line 262 ``` SEE ALSO: rot3,   save3,   restore3

 limit3 ``` limit3, xmin,xmax, ymin,ymax or limit3, xmin,xmax, ymin,ymax, zmin,zmax Set the 3D axis limits for use with the cage. Use keyword aspect=[ax,ay,az] to set the aspect ratios of the cage to ax:ay:az -- that is, the ratios of the lengths of the cage axes will become ax:ay:az. interpreted function, defined at i/pl3d.i line 181 ``` SEE ALSO: cage3,   range3,   plwf,   plwf,   orient3