LeoDraw snapping parts

[Eugen]

As fas I know LeoCAD has grid editing only. So to place those pins in the beams you will need to use a fine (1,1,1) grid.

As for LeoCAD, it has not only grid snapping, but also some sort of "snap ontop (or on the bottom) of a part on its vertical origin axis".

So, if part is rotated to 30deg, and then drag'n'drop the next part on top of it it would be placed directly on top of referenced part and a new added part would use matrix transformation of a part it placed on as well (both parts XY planes would parallel with "Relative Transforms" turned ON).

Limitations:

• New added part would be always placed on top of a part on its origin vertical axis, so "Plate 1x1" would be perfectly placed ontop of "Plate 1x1" and "Plate 1x2 with 1 Centre Stud" (as well as ontop of any odd "Plate 1x[1;3;5;7;...]" or "Plate 3x3", etc.), but if place "Plate 1x1" ontop of simple "Plate 1x2" (with two studs) it would be placed in between two studs (same would be if place it ontop of any even "Plate 1x[2;4;6;8;..]" or "Plate 2x2").
  
• Placing odd-stud plates ontop of also odd-stud plates would be perfect (same for even-stud plates ontop of even-stud plates). For odd-stud plates placed ontop of even-stud plates and vice versa there would always an 1/2 (half) stud mismatch, which could be easy fixed with one extra step move on (if "Snap XY" is set to "1/2 Stud" grid).
  
• Its impossible to place "Plate 1x1" on the end-stud of any plate, instead it requires to move a new placed part along the part it placed on from its center to its end-stud.
  
• For placing on the bottom of referenced part you need rotate 3D view to access referenced part bottom side, and vice versa: to place ontop, 3D view should be adjusted to acces referenced part top side.
  
• If at the centre of referenced part is not a stud, but a pin (or something else, like ball, etc.), a new part would be placed ontop of top side of the bounding box of the refernced part.
  

Here is a screenshot of LeoCAD with a few snapping cases: