Best way to pull this shallow pyramid X shape out by 2 inches?


Attached file, with blue X.
this marks the ridges of an X shaped impression where in thin sheet steel impressing this X shape outwards by 2 inches added stiffening. The rear face also shows the impression, concave/convex in other words.

Its a sort of extremely shallow pyramid, the faces of which have a very slight concavity, not planar, and the X ridges are not sharp. as if after the force was applied they sucked back in a fraction, subtle but there.

what is best way of recreating this, the X impression feathers out at the tips of the blue X.

anyone care to have a stab at it ?

X impression.3dm (56.1 KB)


Hi Steve - something like this?

X impression_PG.3dm (159.7 KB)

You can dent it up a little…

X impression_PG_more.3dm (139.4 KB)


Hi, thats the sort of thing, I need soft edges throughout, so would need fillet the four ‘edges’.

I had a stab at it, drew the north south profile for the north south triangles, created a surface left to right. trimed out the north and south triangles, duped edges and created profiles for the east west by flattening to cplane the dup edge.
and extruded that as a surface
then trimmed out the triangles from this using the X.
joined them, created a solid adding a thin ‘box’ on the back to alllow for filletedge, same thickness as the sheet, then used fillet edge and went from 2 to 0 on each X.

So how did you do yours ?

I like the idea of a bit of battering.
X impression_S.3dm (168.7 KB)

Hi Steve - a few ways are possible -

  • I used your X, with an kink inserted (InsertKink) to each where they meet, and pulled the resulting points out 2" to make the pyramid.

  • Then, four lines, red, from the point to the mid of each edge. ChangeDegree to 2 or 3 and move the interior points inward a little to make the concavity.

  • Loft four triangular surfaces, one for each side.

  • MergeSrf all of these with ‘Roundness’ set to taste - .1 is a little sharper corners on the pyramid, .25 softer, etc.

  • Merging eventually leaves you with one surface that has some soft corners and one hard corner left at the seam. InsertKnot in the radial direction on either side of this seam - space them to visually match the spacing on the merged edges - you’ll see that that process also adds knots.

  • Then, MakePeriodic to round that last sharp edge.

  • InsertKnot in the around direction out near the edge, maybe two knots fairly close together.

  • Use the surface edge to trim out the planar surface and then MatchSrf to that edge to soften the transition there.