I noticed the ledge some time ago when sorting parts back into their sets, and also that the thickness of the material except for most walls is thinner - about 3 LDU. This is consistent across all part variations. I think studs are also slightly taller than 4 LDU as well.
Also a number of elements have variations in wall thickness and use of stiffeners such as the 1 X 4 brick.
For this element, there are many different combinations of wall thickness and ribs or raised surfaces. I'm guessing this is to subtly change the weight of a commonly used element in order to verify contents of a bag or set by using a scale. I think the little open rectangle on some 1 x 1 'headlight' bricks is due to this - a combination of thinner wall and accommodating the connecting stud on the bottom. I have some where this is feature is closed, but very, very thin.
I don't think these variations are necessarily important for LDraw as the 4 LDU material thickness seems to have been around a long time, and established parts probably ought not to be updated.
Any feature that would cause an incorrect collision should be modeled however. I would say that this should include the inside ledge on longer slopes in as much as the visible notches on longer inverted slopes. Also, I noted once that an axle-hole should accommodate a 4LDU diameter tube, I don't know if the axle-holes had been updated to correct this or not.
Also a number of elements have variations in wall thickness and use of stiffeners such as the 1 X 4 brick.
For this element, there are many different combinations of wall thickness and ribs or raised surfaces. I'm guessing this is to subtly change the weight of a commonly used element in order to verify contents of a bag or set by using a scale. I think the little open rectangle on some 1 x 1 'headlight' bricks is due to this - a combination of thinner wall and accommodating the connecting stud on the bottom. I have some where this is feature is closed, but very, very thin.
I don't think these variations are necessarily important for LDraw as the 4 LDU material thickness seems to have been around a long time, and established parts probably ought not to be updated.
Any feature that would cause an incorrect collision should be modeled however. I would say that this should include the inside ledge on longer slopes in as much as the visible notches on longer inverted slopes. Also, I noted once that an axle-hole should accommodate a 4LDU diameter tube, I don't know if the axle-holes had been updated to correct this or not.
- Greg
"The only stupid question is the one that remains unasked"
"The only stupid question is the one that remains unasked"