Documentation / Node reference / geo nodes
Shows which faces of a model would print over thin air, and how much overhang area there is.
Helpers
A 3D printer builds a model layer by layer, and each layer can only reach a little way past the one below it. A face that leans further than that has nothing to print on and needs support. This node finds those faces and joins them into regions. An angle of 0 is a vertical wall, 90 is a ceiling facing straight down, and most printers manage up to about 45.
A region is a set of faces joined by their edges, each past the limit or just short of it (the soft band). One small face just past the limit prints, because its neighbours hold it up, so a region that small is left out. A large area just short of the limit can still sag, so a soft region that large is kept.
The mesh is not changed. The faces of the regions that need support go into a primitive group. Each face gets an OVERHANG_AMOUNT from 0 at the limit to 1 facing straight down, OVERHANG_REGION says which region it is in (0 for none), and OVERHANG_SEVERITY says how bad its whole region is, from 0 to 1. To see them, follow this node with geo/AttributePromote (from PRIMITIVE to POINT, mode MAX, so each point shows the worst face touching it) and a geo/AttributeDisplay on any of the three; OVERHANG_REGION is a whole number, so set the display's attributeType to U32. To keep only the faces that need support, follow it with geo/Delete on PRIMITIVE, group overhang, invert on.
The bed is the lowest point of the input along the up direction. Faces lying on it are bed contact, not overhang, even though they face straight down.
The totals are published as stage attributes, with areas in square millimetres whatever the scene unit: OVERHANG_AREA, OVERHANG_FACES_COUNT, OVERHANG_REGIONS_COUNT, OVERHANG_LARGEST_REGION_AREA and BED_CONTACT_AREA. Read them with attrib(.OVERHANG_AREA, entityType=.STAGE) to compare orientations: turn the model, and the smaller number needs less support.
You can say where support may go. Give the faces a SUPPORT_COST attribute: 0 where anything goes, 1 as usual, higher where you would rather not have it (faces without it cost 1). Put the faces support must never touch, such as the face of a bust, in a supportForbidden group. OVERHANG_WEIGHTED_AREA then adds up the overhang area times its cost, and OVERHANG_FORBIDDEN_AREA the overhang area in that group: turn the model until the forbidden area is 0, then keep the turn with the smallest weighted area. To see where the forbidden overhang is, follow this node with geo/GroupCombine, INTERSECT of overhang and supportForbidden.
Put it before geo/PrintPrepare, on the model the way you see it in the scene. Triangle, quad and hexagon meshes are measured; anything else passes through unchanged.
| Name | Type | What it does |
|---|---|---|
| upDirection | Vector3 | The direction the printer builds in, in the scene. +Y for a scene that is Y-up, which is what you want before geo/PrintPrepare turns the model for the slicer. |
| maxOverhangAngle | Float | How far a face may lean past vertical and still print without support, in degrees. 45 suits most printers; a well-cooled printer may manage 50 or more. |
| softBand | Float | How many degrees short of the limit a face still joins a region. It lets a large area that is only just printable show up, and it is how far past the limit a small region must lean before it counts. 0 turns regions off: every face past the limit counts on its own. |
| minRegionArea | Float | Regions smaller than this, in square millimetres, are left out when they are only a little past the limit: their neighbours hold them up. |
| softBandMinArea | Float | A region made only of faces just short of the limit needs support when it is at least this large, in square millimetres. |
| costAttributeName | AttributeName | The primitive attribute that says what support costs on each face: 0 where anything goes, 1 as usual, more where you would rather not have it. Faces without it cost 1. A point attribute of that name also works, averaged over each face's corners. |
| forbiddenGroupName | String | The primitive group where support must never touch, such as the face of a bust. Overhang in it is added up as OVERHANG_FORBIDDEN_AREA. Leave it empty to skip it. |
| sceneUnit | UInt8 MILLIMETER · CENTIMETER · METER · INCH | What one unit in the scene means, so the areas and the bed tolerance are in millimetres. Use the same value as geo/PrintPrepare. |
| bedTolerance | Float | How close to the bed a face has to be to count as resting on it, in millimetres. |
| groupName | String | The primitive group the overhanging faces go into. Leave it empty to skip the group. |
| amountAttributeName | AttributeName | The primitive attribute that says how far past the limit each face leans: 0 at the limit or below, 1 facing straight down. |
| regionAttributeName | AttributeName | The primitive attribute that numbers the regions from 1. Faces in no region get 0. |
| severityAttributeName | AttributeName | The primitive attribute that says how bad each face's whole region is, from 0 to 1. Unlike the amount, it also shows a large region that is just short of the limit. |
| allocator | UInt8 TEMP · POOL · FLAT_POOL | Which allocator backs the scratch buffers: a pool clears at the end of the cook, temp at the end of the frame. |
Scenes you can open in the editor that teach this node.
A mushroom and a shelf bracket, as modelled at the back and turned by geo/PrintOrient at the front, coloured by the overhang that needs support: the turned parts need none. A third bracket may only take the turns kept from geo/PrintDownDirection's arrows.
geo/PrintOrient geo/PrintDownDirection geo/PrintOverhangMeasure
A ball, a T and a cube on its edge, measured for the faces a 3D printer cannot build without support, and shown four ways: how far each face leans, how bad each region is, which region each face is in, and the surfaces a support would hold up.
geo/PrintOverhangMeasure geo/AttributePromote geo/AttributeDisplay geo/Delete
This page is generated from the engine, so it describes the release you can download. The same text is in the editor's Help panel next to the node itself.
