gkjohnson/three-edge-projection

Visible geometry edge projection and flattening based on three-mesh-bvh.

three-edge-projection

Edge projection based on three-mesh-bvh to extract visible projected lines along the y-axis into flattened line segments for scalable 2d rendering. Additonally includes a silhouette mesh generator based on clipper2-js to merge flattened triangles.

Examples

Geometry edge projection

Silhouette projection

Floor plan projection

Use

Generator

More granular API with control over when edge trimming work happens.

const generator = new ProjectionGenerator();
generator.generate( geometry );

let result = task.next();
while ( ! result.done ) {

	result = task.next();

}

const lines = new LineSegments( result.value, material );
scene.add( lines );

Promise

Simpler API with less control over when the work happens.

const generator = new ProjectionGenerator();
const geometry = await generator.generateAsync( geometry );
const mesh = new Mesh( result.value, material );
scene.add( mesh );

API

ProjectionGenerator

.sortEdges

sortEdges = true : Boolean

Whether to sort edges along the Y axis before iterating over the edges.

.iterationTime

iterationTime = 30 : Number

How long to spend trimming edges before yielding.

.angleThreshold

angleThreshold = 50 : Number

The threshold angle in degrees at which edges are generated.

.includeIntersectionEdges

includeIntersectionEdges = true : Boolean

Whether to generate edges representing the intersections between triangles.

.generate

*generate(
	geometry : MeshBVH | BufferGeometry,
	options : {
		onProgress: ( percent : Number ) => void,
	}
) : BufferGeometry

Generate the edge geometry using a generator function.

.generateAsync

generateAsync(
	geometry : MeshBVH | BufferGeometry,
	options : {
		onProgress: ( percent : Number ) => void,
		signal: AbortSignal,
	}
) : Promise<BufferGeometry>

Generate the geometry with a promise-style API.

SilhouetteGenerator

Used for generating a projected silhouette of a geometry using the clipper2-js project. Performing these operations can be extremely slow with more complex geometry and not always yield a stable result.

.iterationTime

iterationTime = 10 : Number

How long to spend trimming edges before yielding.

.doubleSided

doubleSided = false : Boolean

If false then only the triangles facing upwards are included in the silhouette.

.sortTriangles

sortTriangles = false : Boolean

Whether to sort triangles and project them large-to-small. In some cases this can cause the performance to drop since the union operation is best performed with smooth, simple edge shapes.

.output

output = OUTPUT_MESH | OUTPUT_LINE_SEGMENTS | OUTPUT_BOTH

Whether to output mesh geometry, line segments geometry, or both in an array ( [ mesh, line segments ] );

.generate

*generate(
	geometry : BufferGeometry,
	options : {
		onProgress: ( percent : Number ) => void,
	}
) : BufferGeometry

Generate the geometry using a generator function.

.generateAsync

generateAsync(
	geometry : BufferGeometry,
	options : {
		onProgress: ( percent : Number ) => void,
		signal: AbortSignal,
	}
) : Promise<BufferGeometry>

Generate the silhouette geometry with a promise-style API.