#547 shade_surf performance

[Martin Svec]

shade_surf works very differently from the one in IDL

Try
shade_surf,dist(10,10) in GDL to see triangles of various shades where it shouldn't be

Also, with a high number of points GDL is considerably slower,
try:
shade_surf,dist(1000,1000)

The shades are weird, also.
btw. Missing much the "perspective" keyword

[giloo]

Hi,

Shade_surf is mostly an interface to plplot's plsurf3d() function which is a long way from a real shading (which should be done in the GPU anyway). The position of the light source can be changed ( due to an error in gdl this position is in pixels, not in relative coordinates, but this will soon be corrected).
In general all the plplot functions are slow, and plplot shading (fill, contours, etc) is particularly inefficient. But plplot has other advantages which fit most of the general GDL useages...

[giloo]

closed as we cannot do much here, please contact plplot.