0031605: gp_GTrsf::SetVectorialPart sets scale to 0.0 causing non-invertable matrix

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0031605

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[OCCT] OCCT:Foundation Classes

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2020-06-10 11:42

Reporter

aothms

Assigned To

abv

Priority

normal

Severity

minor

Status

new

Resolution

open

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Fixed in Version

Summary

0031605: gp_GTrsf::SetVectorialPart sets scale to 0.0 causing non-invertable matrix

Description

I sometimes get a 4x4 matrix from external sources that I want to convert to a shape location. So I use gp_GTrsf, check form, convert to gp_Trsf and TopLoc_Location.

The most straightforward way to do this is to use gp_GTrsf::SetVectorialPart(), but that sets the internal scale value to 0.0. I don't think this is necessary: there is code in OCCT to calculate scale from the gp_Mat I think and I also don't know why gp_GTrsf carries a single scale value as it allows non-uniform scale.

I'd happily provide a fix if I get some guidance on the most desirable way to address this.

Steps To Reproduce

Execute the code below and witness an exception in gp_Trsf::Invert()

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#include <gp_Mat.hxx>
#include <gp_GTrsf.hxx>
#include <TopLoc_Location.hxx>
#include <BRep_Tool.hxx>
#include <BRepBuilderAPI_MakeFace.hxx>
#include <gp_Pln.hxx>
#include <TopoDS_Face.hxx>
#include <TopExp_Explorer.hxx>
#include <TopoDS.hxx>
#include <TopoDS_Edge.hxx>

int main(int, char**) {
    gp_Mat mat(gp::DX().XYZ(), gp::DY().XYZ(), gp::DZ().XYZ());
    gp_GTrsf trsf;
    trsf.SetVectorialPart(mat);
    trsf.SetForm();
    TopLoc_Location loc(trsf.Trsf());

    TopoDS_Face f = BRepBuilderAPI_MakeFace(gp_Pln(), 0.1, 0.1, 0.2, 0.2).Face();
    f.Move(loc);
    TopExp_Explorer exp(f, TopAbs_EDGE);
    TopoDS_Edge e = TopoDS::Edge(exp.Current());

    double u0, u1;
    BRep_Tool::CurveOnSurface(e, f, u0, u1);
}
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Issue History
Date Modified	Username	Field	Change
2020-06-10 11:42	aothms	New Issue
2020-06-10 11:42	aothms	Assigned To	=> abv

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