I think it is long overdue for a general method for constraining the origin and orientation for both 2D (pattern & hatching) and 3D (materials) on an element element-by-element basis.

This is important because often patterning/hatching needs to be accurately and thoughtfully aligned to its host geometry when used to indicate real world setting out of tessellating components (panels/bricks/paving/etc).

However, origin control is hit and miss especially where patterning is automatically generated, and just error prone where manually manipulated - especially where the host elements are updated and editing the pattern info is a secondary operation.

I think the "anchor" for patterning we only need two dimensions (point=origin, vector=orientation) as the third-dimension constraint is the planar surface that is being patterned.

I can see that this anchoring of pattern origin/orientation could be relative to a specified element (eg a special construction line, or one of the boundary segments.) this would work well with 2D constraint modelling eg to centre a ceiling pattern over a room shape/space.

It could just as easily be a marker style widget that only shows up when required, but retains the associative link and relative offset/rotation from some know element. However, I think I like the constraint option more because it would have legs in the construction of parametric cells.

For 3D this could drive the positional mapping tool for materials in a more useful way. The current position mapping tools are not accurate enough to easily orientate/align patterning to the surfaces of 3D geometry (ie they are ok to eyeball a pattern into place but not pinpoint accurate) - this is important for dynamic cut view where geometry maps generate drawing info in cached views.

It would also be useful for display rules, where a rule is created to pattern an area on the fly, but there is currently no way to determine where the pattern end up on the shape/surface.

Regards

Robert