Inferencing on a thin slab

[pipingguy]

If i have a thin slab, and I begin using the circle, rectangle, line etc tool to draw on its face, the inferencing engine will pick up any object that may be in contact with the bottom of the slab. It will not restrict itself to the plane of the face. Same goes for the query tool. This happens when the camera is at some distance only. Actually, I believe this same reaction happens with the move command - i think I am grabbing the top edge of a thin slab - when in reality, I am grabbing the bottom edge. Again - only when the camera is at some distance. This came to light as i was maneuvering some wide flange beams so they were all flush with eachother on top. The beam's top flanges are relatively thin. And as I was checking the elevations of the beam's tops with the query tool, I was getting unexpected results.

[Rich O Brien]

If the distance between geometry is subpixel compared to the viewport then you will encounter this behaviour in 3D. Its not unique the SketchUp.

Similar to camera clipping there are limitations to what you can show and what you can see.