Geometry Tagging: Essential Knowledge

This section explains concepts fundamental to geometry tagging.

Component Tags

Tags are string-based information stored directly on the topological components of a shape's geometry asset. Each face, edge, and vertex may have an arbitrary number of tags. Their purpose is to identify semantically different parts of the geometry, for example when using the comp operation.

A tag is a string that defines its name. Example: "Name"

Tag hierarchy

Tags are hierarchically grouped with the name separator "." (dot). Example: "Name1.Name2", "Name1.Name3"

The dot-separated names within a tag are referred to as subtags.

Tag queries

A tag query is a string that may include wildcards to replace subtags. There are two wildcards:

? (question mark)	Matches exactly 1 subtag. Example: "?.Name"
* (asterix)	Matches 1 or more subtags. Example: "Name1.*.Name2"

Based on the hierarchical grouping, the tag query "Name1" matches not only the exact tag "Name1" but also tags with additional subtags, such as "Name1.Name2", "Name1.Name2.Name3".

Auto-Tags

Selected geometry creation operations automatically apply predefined tags. These tags identify semantically different parts of the output geometry.

Auto-tags applied by a certain operation remain accessible until the operation is called again, replacing them with new ones.

Operations applying auto-tags on faces

Face components are categorized into three principle types: bottom, side, and top. The bottom components correspond to the original faces, while the new side faces may be further categorized as either inner or outer, depending on whether they emanate from a hole.

Extrude

Init --> 
    extrude(4)
    comp(f) { isTagged("extrude.bottom")     : Blue 
            | isTagged("extrude.side.outer") : Yellow
            | isTagged("extrude.side.inner") : Red
            | isTagged("extrude.top")        : Green }

See extrude operation.

Envelope

Init --> 
    envelope(normal,4, 2.5,45, 3,45, 3.5,50, 2,50)
    comp(f) { isTagged("envelope.bottom")     : Blue 
            | isTagged("envelope.side.base")  : Yellow
            | isTagged("envelope.side.slope") : Orange
            | isTagged("envelope.side.inner") : Red
            | isTagged("envelope.top")        : Green }

See envelope operation.

Taper

Init --> 
    taper(4)
    comp(f) { isTagged("taper.bottom") : Blue 
            | isTagged("taper.side")   : Yellow }

See taper operation.

Roofs

All roof operations apply the same base tag "roof".

RoofAutoTags -->
    comp(f) { isTagged("roof.bottom") : Blue 
            | isTagged("roof.side")   : Yellow
            | isTagged("roof.top")    : Green } 

Init --> 
    roofGable(byHeight, 4)
    RoofAutoTags

See roofGable operation.

	
	
Init --> 
    roofHip(byHeight, 4)
    RoofAutoTags

See roofHip operation.



Init --> 
    roofPyramid(byHeight, 4)
    RoofAutoTags

See roofPyramid operation.

RoofAutoTags -->
    comp(f) { isTagged("roof.bottom")     : Blue 
            | isTagged("roof.side.outer") : Yellow
            | isTagged("roof.side.inner") : Red
            | isTagged("roof.top")        : Green } 

Init --> 
    roofRidge(byHeight, 4)
    RoofAutoTags

See roofRidge operation.



Init --> 
    roofShed(byHeight, 4)
    RoofAutoTags

See roofShed operation.

Boolean 3D operations

BoolAutoTags -->
    comp(f) { isTagged("bool.A") : Blue 
            | isTagged("bool.B") : Green } 

Sphere --> t(0.3,0.3,0.3) primitiveSphere()

Init --> 
    extrude(1)
    union Sphere
    BoolAutoTags

See union operation.

Init --> 
    extrude(1)
    subtract Sphere
    BoolAutoTags

See subtract operation.

Init --> 
    extrude(1)
    intersect Sphere
    Sphere --> t(0.3,0.3,0.3) primitiveSphere()

See intersect operation.

Operations applying auto-tags on edges

The setback operation and its variants — setbackToArea, setbackPerEdge, shapeLUO and splitAndSetbackPerimeter — automatically tag edge components using the same base "setback".

Shape

ShapeAutoTags -->
    comp(e) { isTagged("setback.front") : Blue 
            | isTagged("setback.side")  : Yellow
            | isTagged("setback.back")  : Green }

Init --> 
    setback(4) { front : ShapeAutoTags }

Remainder


RemainderAutoTags -->
    comp(e) { isTagged("setback.side")      : Yellow
            | isTagged("setback.back")      : Green 
            | isTagged("setback.remainder") : Purple }
Init --> 
    setback(4) { front     : NIL
               | remainder : RemainderAutoTags }

Tag propagation

In general, geometry-modifying operations preserve tags on existing components and propagate tags to newly constructed components when applicable.

Geometry subdivision

Subdivided edge and face components keep their tags. Newly constructed components have no initial tags.


Init --> 
    roofGable(byHeight, 4)
    split(z) { ~2 : RoofAutoTags }*

Here the auto-tags applied by the roofGable operation are kept by the split operation.

Face tag propagation

New faces constructed on top of existing ones get the tags of their source face.


Init --> 
    roofGable(byHeight, 4)
    extrude(1)
    RoofAutoTags

Here the auto-tags applied by the roofGable operation are automatically propagated to the new faces constructed by the extrude operation.

Edge tag propagation

New faces emanating from existing edges get the tags of their source edge.

SetbackAutoTagsOnFaces -->
    comp(f) { isTagged("setback.side")      : Yellow
            | isTagged("setback.back")      : Green 
            | isTagged("setback.remainder") : Purple
            | all                           : White }
Init --> 
    setback(4) { front     : NIL
               | remainder : Extrude }
Extrude --> extrude(4)
            SetbackAutoTagsOnFaces

Here the edge auto-tags applied by the setback operation are automatically propagated to the extruded side faces.


Init --> 
    setback(4) { front     : NIL
               | remainder : Envelope }
Envelope --> envelope(normal, 4, 2.5, 45, 3, 45, 2, 50, 2, 50)
             SetbackAutoTagsOnFaces

Example envelope operation.


Init --> 
    setback(4) { front     : NIL
               | remainder : Offset }
Offset --> offset(-2)
           SetbackAutoTagsOnFaces

Example offset operation.

Also see the setTagsFromEdgeAttrs operation for more examples.

Geometry cleanup

The cleanupGeometry operation maintains existing tags, preventing the removal of tagged edges and edges between faces with different tags.

Init --> 
    setback(4) { front     : NIL
               | remainder : OffsetCleanup }
               
OffsetCleanup --> offset(-2)
                  cleanupGeometry(all, 0)
                  SetbackAutoTagsOnFaces

The cleanupGeometry operation only merges faces with the same tags.

Operations that clear all tags

By design

These operations replace the current shape's geometry asset, thus existing component tags are cleared.

i (insert), insertAlongUV operations
primitiveXXX operations
footprint operation
resetGeometry operation

Unsupported

These operations do (currently) not support working with component tags and clear all tags.

splitArea operation
scatter operation
reduceGeometry operation