Figure 5-12Note that surfaces will retain their surface definitions, so if the objects used in a CSG operation had different surface definitions, the resulting object may have different surfaces on different parts. In the example below the "hollow" created from the chess piece has the chess piece object's surface whereas the rest of the box uses Rayshade's default surface.
The most common problem that occurs when constructing CSG objects comes from one (or both) the objects not being properly closed.
The image below, has a number of errors and inconsistencies, including incorrect surface colouring and extraneous interior surfaces. Refer to figure 5-5 to see how the image should look!
Figure 5-12
/*
csg-prob.ray
csg problems:
chess piece constructed using list should not be used
in CSG when it includes overlapping shapes.
Stephen Peter 8 mar 92
*/
eyep 150 50 150
lookp -15 0 45
background .9 .9 .9
light .5 point 250 0 150
screen 400 800
fov 20 37
surface salmon
ambient .2 .1 .1
diffuse 1 .5 .45
specular .3 .3 .3
name chess_piece
list
disc 25 0 0 0 0 0 -1
cylinder 25 0 0 0 0 0 4
disc 25 0 0 4 0 0 1
cone 25 0 0 4 22 0 0 15
cone 19 0 0 15 3 0 0 95
disc 15 0 0 62 0 0 -1
cylinder 15 0 0 62 0 0 66
disc 15 0 0 66 0 0 1
sphere 14.75 0 0 77
end
difference
box 0 -30 -10 -30 30 100
object salmon chess_piece
end
A more subtle problem can occur when the objects have surfaces that coincide.
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THE END - Notes on Rayshade - 5 - CSG Problems