# Silhouette Edges

Silhouette Edges
Field: Geometry
Image Created By: Steve Cunningham

Silhouette Edges

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# A More Mathematical Explanation

Note: understanding of this explanation requires: *Graphics

If you have a 3D object, either surface or solid, a silhouette edge is the collection of points where [...]

If you have a 3D object, either surface or solid, a silhouette edge is the collection of points where the surface normal is orthogonal to the view vector.

If the object is composed of facets, a silhouette edge is comprised of the common edges between a facet whose surface normal points toward the viewer and a facet whose surface normal points away from the viewer. This is then an algorithm for finding silhouette edges:

For every facet in the object
Compute the surface normal of the facet
If the surface normal points toward the viewer
For every edge of the facet
Identify the facet that shares this edge
Compute the surface normal for that facet
If this surface normal points away from the viewer
Add the edge to the collection of silhouette edges
endif
endfor
endif
endfor

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