How to get a contour of a plane intersecting a mesh?

[nsmela]

Hey there,

Stuggling to figure out which functions to use to get the contours of a plane intersecting a mesh. Ideally, itd return an ordered list of vectors for each edge loop and could quickly be triangulated for a mesh.

[Grantim]

Hello!

This function should work

MeshLib/source/MRMesh/MRExtractIsolines.h

Lines 26 to 27 in d822522

	/// extracts all plane sections of given mesh
	[[nodiscard]] MRMESH_API PlaneSections extractPlaneSections( const MeshPart & mp, const Plane3f & plane, UseAABBTree u = UseAABBTree::Yes );

Could you please specify what do you mean by triangulate? Do you mean separate planar mesh based on the sections or do you want to trim original mesh and triangulate planar holes?

[nsmela]

Thanks!

I'd like to 1) use the edges to generate a visual representation of the contour using cylinders for edges and spheres for points, and 2) generate a mesh of the contour holes instead of using cylinders and spheres.

[Grantim]

In this case code like this should generate the mesh:

from meshlib import mrmeshpy as mm

mesh = mm.makeUVSphere()
plane = mm.Plane3f.fromDirAndPt(mm.Vector3f(1,1,1).normalized(),mm.Vector3f(0,0.2,-0.4))

sections = mm.extractPlaneSections(mesh,plane)
contours3 = mm.surfacePathsToContours3f(mesh,sections)

xfTo3d = mm.getXfFromOxyPlane(contours3)
xfTo2d = xfTo3d.inverse()

conts2 = mm.Contours2f()
conts2.resize(contours3.size())
for i in range(len(conts2)):
    conts2[i].resize(contours3[i].size())
    for j in range(len(conts2[i])):
        pt = xfTo2d(contours3[i][j])
        conts2[i][j] = mm.Vector2f(pt.x,pt.y)

section_mesh = mm.PlanarTriangulation.triangulateContours(conts2)
section_mesh.transform(xfTo3d)

[nsmela]

Great, thank you!