PointOnSurface from TIN

[schoeller]

Dear all,

I am trying to derive a PointOnSurface object from a tin or surface and run into trouble. The last line throws.

Hints welcome

Seb

        # Select TIN
        es = Ed.Editor.entSel("\nSelect TIN: ", Cv.CvDbTinSurface.desc())
        if es[0] != Ed.PromptStatus.eOk:
            raise RuntimeError("Yeet! {}: ".format(es[0]))
        tin_ids = [es[1]]

        # Convert tin to surface 
        tin = Cv.CvDbTinSurface(tin_ids[0])
        sbmesh = tin.subDMesh()
        surface = sbmesh.convertToSurface(False, False)

        # Create PointOnSurface object and set surface
        ptos = Ge.PointOnSurface()
        ptos.setSurface(surface)

[CEXT-Dan]

Ah Db.Surface VS Ge.Surface, I don’t think there’s a direct conversion. Maybe using Brep?

import traceback
from pyrx import Ap, Br, Db, Ed, Ge, Cv

def get_ge_surfaces_from_db_surface(db_surface):
    ge_surfaces = []
    brep = Br.Brep(db_surface)
    traverser = Br.FaceTraverser(brep)
    for face in traverser.getFaces():
        ge_surf = face.getSurface()
        ge_surfaces.append(ge_surf)
    return ge_surfaces

@Ap.Command()
def doit():
    try:
        ps, id, _ = Ed.Editor.entSel("\nSelect TIN: ",Cv.CvDbTinSurface.desc())
        if ps != Ed.PromptStatus.eOk:
            raise RuntimeError("Yeet! {}: ".format(ps))

        tin = Cv.CvDbTinSurface(id)
        sbmesh = tin.subDMesh()
        surface = sbmesh.convertToSurface(False, False)
        
        for ges in get_ge_surfaces_from_db_surface(surface):
            ptos = Ge.PointOnSurface(ges)
            print(ptos.point3d())

    except Exception:
        traceback.print_exc()

[schoeller]

For a known point located on a tin object I did as follow finding the normal vector.

   tri = tin.findTinTrianglesAt(pt)
    if len(tri):
        quit
    ctri = tri[0]
    face = Db.Face(ctri.locationAt(0), ctri.locationAt(1), ctri.locationAt(2))
    plane = face.getPlane()
    vec = plane.normal()

or as mistral puts it:

if tri := tin.findTinTrianglesAt(pt):
    ctri = tri[0]
    face = Db.Face(*(ctri.locationAt(i) for i in range(3)))
    plane = face.getPlane()
    vec = plane.normal()

[CEXT-Dan]

If I’m reading it correctly, to find the normal of that triangle it might be faster to use math or if you need a plane to test other intersections

    ab: Ge.Vector3d = b - a
    ac: Ge.Vector3d = c - a
    normal = ab.crossProduct(ac)
    
    # or if you need a plane
    bp = Ge.BoundedPlane(a,ab,ac)
    bp.normal()

[CEXT-Dan]

I added to CvTinTriangle
TinTriangle.aspect
TinTriangle.isPointInside
TinTriangle.plane
TinTriangle.slope
TinTriangle::centroid
TinTriangle::circumcenter
TinTriangle::normal, this should always be an up vector, no matter the winding ?