Channels & points

Points and channels are what a fluid network is made of. A point is a terminal — a place a channel can end. A channel is the connection between two of them.

Nothing else connects. A channel always ends at a point, never at another channel and never at a region, so a junction is a point that several channels share, and a chamber is reached through a point riding its wall.

Points

A point is a position and a set of properties, and it fabricates nothing on its own — it shows in the viewport as a marker rather than as geometry.

A point carries a width. Channel ends connected to it inherit that width, so a run through a point stays one width and editing the point moves every inherited end together. An end that sets its own width overrides the point’s, which is how you author a taper or a junction arm narrower than the run it leaves.

A point also records a layer span (span lo and span hi), the slabs it reaches through, with lo at or below hi. The span is authoring intent shown in the view; the exported geometry is built from the channels and regions around the point.

A free point sits where you place it and accepts any number of channels. A wall-bound point rides one edge of a sibling region’s wall and accepts at most one, since it is a break-in through that wall. Binding is a property of the point, not of the channel: a channel adopts either kind the same way, and either can be exposed as a pin.

Channels

A channel is one connection, whatever shape it takes. A long run with five bends between two junctions is a single channel — one child in the body, one row in the Body tab, one thing to select, name and delete.

Its shape is a centerline polyline: the two ends, plus the interior vertices you place between them. The ends are the contract, anchored to the points they connect. The interior vertices are geometry, and deleting one straightens the channel through it.

Width is a value at each vertex, interpolated between them. Give the two ends different widths and the channel tapers along its length; give an interior vertex its own width and the taper turns there. An end with no width of its own inherits from its point.

Channel ends

An end attaches to a pin or a point — either one you already have, or one the drawing gesture creates for you. Ending in empty space creates a point there. Ending on the body of another channel splits that channel at the click and puts a new point between the two halves. Either way the whole gesture is one undo step: the channel you drew and everything it created come back together.

Bends and junctions

Several channel ends may name one free point, and that point is the junction — a T, a cross, or the four-armed node inside a flow-focusing component. Nothing merges after the fact: two separate points never collapse into one, so a junction is always a terminal that was shared deliberately.

An interior vertex is a bend rather than a junction, and nothing can attach to it. Promote to point on the right-click menu turns one into a junction, splitting the channel there into two channels meeting at a new point. Dissolve into channel is the reverse: a point where exactly two channels meet collapses back into a single channel through it, and the item is disabled with a reason where the point does not qualify.

Neither changes the fabricated shape. A point where two channels meet straight through is mitered exactly as the bend it replaced, so the boundary between bend and junction is yours to move as a design takes shape.

Region-wall landings

A channel reaches a chamber or a reservoir by ending at a wall-bound point, which rides one edge of that region’s wall. The channel breaks through the wall there, and the two shapes meet along an exact stretch of the edge with no material between them.

A landing has to fit the wall it sits on. It keeps at least half the channel’s width clear of each corner of the edge, sliding along rather than letting the opening run off the end, and a wall edge shorter than the channel is wide takes no landing at all.

A wall-bound point with no channel on it is a wall tap — a marked landing spot that opens nothing. Built-in components expose their taps as pins, so a chamber arrives with inlet and outlet already placed on its wall and the wall still closed until you connect something.

See also

• Regions & compartments — the walls a channel lands on.
• Components, parameters & pins — how a point becomes a pin.
• Inspector — the ends block, the vertex detail and the point detail.
• Toolbar & tools — the Draw channel, Add point and Insert vertex tools.