mirror of
https://github.com/BelfrySCAD/BOSL2.git
synced 2025-01-01 09:49:45 +00:00
134 lines
3.1 KiB
OpenSCAD
134 lines
3.1 KiB
OpenSCAD
use <math.scad>
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function winding_dir(points, face) =
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let(count=len(face))
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sum(
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[
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for(i=[0:count-1]) cross(
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points[face[(i+1)%count]]-points[face[0]],
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points[face[(i+2)%count]]-points[face[(i+1)%count]]
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)
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],
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0
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)
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;
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function find_convex_vertex(dir, points, face, i=0) =
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let(count=len(face),
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p0=points[face[i]],
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p1=points[face[(i+1)%count]],
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p2=points[face[(i+2)%count]]
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)
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(len(face)>i)?
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(cross(p1-p0, p2-p1)*dir>0)? (i+1)%count : find_convex_vertex(dir, points, face, i+1)
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: //This should never happen since there is at least 1 convex vertex.
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undef
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;
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function point_in_ear(points, face, tests, i=0) =
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(i<len(face)-1)?
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let(
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prev=point_in_ear(points, face, tests, i+1),
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test=check_point_in_ear(points[face[i]], tests)
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)
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(test>prev[0])? [test, i] : prev
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:
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[check_point_in_ear(points[face[i]], tests), i]
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;
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function check_point_in_ear(point, tests) =
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let(
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result=[
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(point*tests[0][0])-tests[0][1],
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(point*tests[1][0])-tests[1][1],
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(point*tests[2][0])-tests[2][1]
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]
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)
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(result[0]>0 && result[1]>0 && result[2]>0)? result[0] : -1
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;
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function normalize_vertex_perimeter(v) =
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(len(v) < 2)? v :
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(v[len(v)-1] != v[0])? v :
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[for (i=[0:len(v)-2]) v[i]]
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;
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function triangulate_faces(points, faces) =
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[
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for (i=[0 : len(faces)-1])
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let(facet = normalize_vertex_perimeter(faces[i]))
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for (face = triangulate_face(points, facet))
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if (face[0]!=face[1] && face[1]!=face[2] && face[2]!=face[0]) face
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]
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;
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function is_last_off_a_line(points, facelist, vertex) =
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let(
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face=wrap_range(facelist, vertex+1, vertex-1),
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count=len(face),
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dir=winding_dir(points, face)
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)
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0==sum(
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[
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for(i=[0:count-1]) norm(
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cross(
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points[face[(i+1)%count]]-points[face[0]],
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points[face[(i+2)%count]]-points[face[(i+1)%count]]
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)
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)
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]
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)
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;
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function triangulate_face(points, face) =
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let(count=len(face))
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(3==count)?
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[face]
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:
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let(
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dir=winding_dir(points, face),
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cv=find_convex_vertex(dir, points, face),
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pv=(count+cv-1)%count,
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nv=(cv+1)%count,
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p0=points[face[pv]],
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p1=points[face[cv]],
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p2=points[face[nv]],
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tests=[
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[cross(dir, p0-p2), cross(dir, p0-p2)*p0],
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[cross(dir, p1-p0), cross(dir, p1-p0)*p1],
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[cross(dir, p2-p1), cross(dir, p2-p1)*p2]
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],
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ear_test=point_in_ear(points, face, tests),
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clipable_ear=(ear_test[0]<0),
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diagonal_point=ear_test[1]
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)
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(clipable_ear)? // There is no point inside the ear.
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is_last_off_a_line(points, face, cv)?
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// In the point&line degeneracy clip to somewhere in the middle of the line.
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flatten([
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triangulate_face(points, wrap_range(face, cv, (cv+2)%count)),
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triangulate_face(points, wrap_range(face, (cv+2)%count, cv))
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])
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:
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// Otherwise the ear is safe to clip.
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flatten([
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[wrap_range(face, pv, nv)],
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triangulate_face(points, wrap_range(face, nv, pv))
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])
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: // If there is a point inside the ear, make a diagonal and clip along that.
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flatten([
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triangulate_face(points, wrap_range(face, cv, diagonal_point)),
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triangulate_face(points, wrap_range(face, diagonal_point, cv))
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])
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;
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// vim: noexpandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap
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