I am using surface to load png images. There are a couple of ways that
the results are not as I expected based on the wikibooks user manual. I
have distilled the problematic images down to a simple 3 colour
checkerboard file, test.png inserted below, with two white squares as
rgb 255, 255, 255, one gray as rgb 127, 127, 127, one black as rgb 0,0,0.
Now that I know what's going on, I can see easy ways to circumvent these
two problems. However, because it took me a fairly long time to figure
out why my models weren't shaped as I expected, I'm interested to know
if the problems are bugs or documentation flaws.
Cheers,
Steve
test.png
Problem 1: using the single statement surface("test.png") produces a
shape with maximum z-value of 100 and minium of -1, whereas the
documentation tells me the image's colours will be mapped in the range 0
to 100. It seems that OpenSCAD has perhaps added a base layer/footprint
below the entire shape.
Why does this happen? Is it a necessary/intended behaviour that perhaps
ought to be mentioned in the documentation?
Problem 1 screenshot
Problem 2: using the single statement surface("test.png", invert = true)
gives a shape that is entirely below the z = 0 plane. The documentation
says that the invert parameter "inverts how the color values of imported
images are translated into height values". To me, that wording means the
z values should be calculated using the complement in 100 of the value
obtained from the imported pixel (height = 100 - imported). The heights
would then be in the range 100 to 0, so the shape would still be above
the z = 0 plane.
Again, is actually OpenSCAD carrying out intended behaviour? If so,
should the documentation state that the entire shape is displaced
downwards by the invert=true setting?
Problem 2 screenshot
I am using surface to load png images. There are a couple of ways that
the results are not as I expected based on the wikibooks user manual. I
have distilled the problematic images down to a simple 3 colour
checkerboard file, test.png inserted below, with two white squares as
rgb 255, 255, 255, one gray as rgb 127, 127, 127, one black as rgb 0,0,0.
Now that I know what's going on, I can see easy ways to circumvent these
two problems. However, because it took me a fairly long time to figure
out why my models weren't shaped as I expected, I'm interested to know
if the problems are bugs or documentation flaws.
Cheers,
Steve
test.png
Problem 1: using the single statement surface("test.png") produces a
shape with maximum z-value of 100 and minium of -1, whereas the
documentation tells me the image's colours will be mapped in the range 0
to 100. It seems that OpenSCAD has perhaps added a base layer/footprint
below the entire shape.
Why does this happen? Is it a necessary/intended behaviour that perhaps
ought to be mentioned in the documentation?
Problem 1 screenshot
Problem 2: using the single statement surface("test.png", invert = true)
gives a shape that is entirely below the z = 0 plane. The documentation
says that the invert parameter "inverts how the color values of imported
images are translated into height values". To me, that wording means the
z values should be calculated using the complement in 100 of the value
obtained from the imported pixel (height = 100 - imported). The heights
would then be in the range 100 to 0, so the shape would still be above
the z = 0 plane.
Again, is actually OpenSCAD carrying out intended behaviour? If so,
should the documentation state that the entire shape is displaced
downwards by the invert=true setting?
Problem 2 screenshot
