Module sheet 

The sheet-metal model a body is built from and unfolded with: its SheetMetalRules, and its Sheet — flat faces joined by bends — recorded for the solid it builds (see crate::body::sheets).

Sheet coordinates. Every flat is drawn in one plane of coordinates (x, y), the sheet coordinates, and placed in space by a Placement of its own. A bend joins an edge P of its parent flat to an edge C of its child flat, and the child’s placement is the parent’s turned about the bend’s axis: so C is P in sheet coordinates, and the child lies on the far side of it. Laid flat, every flat keeps its shape and only moves away from its parent by the bend’s developed length (see Sheet::unfolded), which is what makes the flat pattern exact and the unfolding topological: which faces are flat and which are bends is recorded here, never guessed from the geometry.

Sides. The A side is the side drawn — the sketch’s plane or line — and the B side a thickness further along each flat’s normal n. A bend turns towards the B side (toward_b), which is then its inside, or away from it.

Structs

Bend

A bend: a cylindrical strip from the straight edge parent_edge of flat parent to the edge child_edge of flat child — the same segment in sheet coordinates, run the other way.

BendFrame

How a bend turns, worked out from its parent flat: the frame of its first edge and its radii.

Cut

A cut through the sheet (see crate::SheetCut): closed loops, each counter-clockwise around what it takes away, drawn in flat flat’s sheet coordinates — and so, where they reach past the flat, across its bends unrolled.

Flat

A flat face of the sheet: its loops in sheet coordinates — the outer one counter-clockwise about its normal, holes clockwise — and where it lies.

FlatEdge

One edge of a flat’s loop, in sheet coordinates, running the way the loop does. The vertex where it starts is named after it.

Placement

Where a flat lies: sheet point (x, y) at origin + x e1 + y e2, its unit normal n = e1 × e2 pointing from its A side to its B side. e1, e2 and n are orthonormal.

Sheet

A sheet-metal body as it is built: flat faces, the first the one the rest hang off, and the bends joining them into a tree, each child built after its parent.

SheetMetalRules

How a body’s sheet metal is made and bent: what the base flange sets and every flange and the flat pattern of the body follow.

Enums

Relief

What is cut beside a flange narrower than its edge, where the bend would otherwise tear the sheet.

Functions

straight

A straight flat edge from a to b, named name.