I've modelled a hair dryer in Solid Edge for a school assignment and was performing closed (Solid Edge to IGES/STEP to Solid Edge) and open (Solid Edge to IGES/STEP to Autodesk 360 viewer) loop tests with the neutral IGES and STEP formats and I noticed something very strange.
I have a torus body that I added to a complex body with a boolean union operation. (The torus was created with a swept potrusion). When I do the closed loop test, this torus dissappears when I use the IGES format, but not when I'm using STEP. (See the enclosed pictures) Could anyone explain to me why this happens ? (Understanding it is more important than fixing it if possible)
Something curious happened with my open loop test as well. I uploaded both formats to the online Autodesk viewer and when I did so the first time the STEP format was missing the torus but the IGES format did have the torus. But when I uploaded them the 2nd time to get a a good screenshot of this problem (I ony noticed it afterwards) both formats gave the full model (I originally thought that I perhaps mixed up the formats when I did it the first time and that the problem was both times with the IGES format).
A side question:
Why are the colors from my original file changing when I perform these tests with IGES/STEP. I thought colors were defined according to standards (RGB values etc)?
The most reliable translation is Parasolid. IGES is ancient and is open to different interpretations by different vendors. STEP is better than IGES, but not as good as Parasolid. Sometimes partial primitives get interpreted differently depending on tolerances, or settings within the sending and receiving systems.
Colors can be wonky depending on translation format and where you applied the color. Depending on if you applied the color to a feature/face/body/part/occurance, the color translation outcome might be different. You should always apply the color to the part for most consistent results, without having colors applied at other levels.
This all is just part of the history and ambiguity of non-standardization in the CAD industry.