Le 26/01/2016 00:13, Chris Cason a écrit :
> While STL doesn't currently support color information I can see a time
> when this starts to matter more.

The problem is not that there is no color in STL, it is that the *smart* 
*** have forked the specification for the colours in two variants, 
without being able to identify in the file which format was use. (at 
least for binary STL). And they are not compatible at all.

Figure: both format have 16 bits, in "atttribute byte count", one format 
uses it as B5G5R5V+, and the other formats uses it as R5G5B5V-
(V for validity, in contrast to a default colour or anything else)

Blue-Green-Red vs Red-Green-Blue. It's even worst than little vs big 
endian. (Yellow can be badly printed as Cyan and so on)

And as stated in the english wikipedia for stl file format, there is no 
transparency... 15 bits colours is probably too much, that's 32768 colours.

Notice that Shapeways have colour for the sandstone material. I do not 
know which of the two formats they use. But at least for sandstone, 
there is no hope of transparency.

and to finish it: rgb color system... without any gamma specification... 
for printer that are more likely to use cmyk. Pure colours are fine (at 
least the 8 of the cube: red, blue, black...), but beware of 
intermediate ones, your print might not be identical to the preview.

Post a reply to this message