Reading IGES files

Hi Quenan,

I would do that like this:

1. Read Iges file.
2. Use TopExp_Explorer or TopTools_IndexedMapOfShape to find all the faces of the imported shape.
3. For each face obtain the U and V parameters and iterate.
4. At each U-V-point get the surface normal using BRepLProp_SLProps

It would look something like this:

TopTools_IndexedMapOfShape aMap;

BRepClass3d_SolidClassifier solidClassifier(shape);

TopExp::MapShapes(shape, TopAbs_FACE, aMap);

BRepLProp_SLProps surfaceProperties(1, Precision::Confusion());
double u0, u1, v0, v1;
double u, v;
double uDelta, vDelta;

for(int i = 1; i <= aMap.Extent(); i++)
{
BRepAdaptor_Surface surface(TopoDS::Face(aMap(i)));
surfaceProperties.SetSurface(surface);

u0 = surface.FirstUParameter();
u1 = surface.LastUParameter();

v0 = surface.FirstVParameter();
v1 = surface.LastVParameter();

u = u0;
v = v0;

uDelta = surface.UResolution(resolution);
vDelta = surface.VResolution(resolution);

while(u <= u1)
{
v = v0;
while(v <= v1)
{
GetSurfaceProperties(u, v,
surfaceProperties, solidClassifier,
output, propertyToCompute);

v += vDelta;
}
if(v != v1)
{
v = v1;
GetSurfaceProperties(u, v,
surfaceProperties, solidClassifier,
output, propertyToCompute);
}

u += uDelta;
}
if(u != u1)
{
u = u1;
v = v0;
while(v <= v1)
{
GetSurfaceProperties(u, v,
surfaceProperties, solidClassifier,
output, propertyToCompute);

v += vDelta;
}
if(v != v1)
{
v = v1;
GetSurfaceProperties(u, v,
surfaceProperties, solidClassifier,
output, propertyToCompute);
}
}
}

Commenter-1

Hi Pawel,

thank you for your quick answer, and sorry for mine, arriving a little bit late.

But i don't understand some parts of your code.

First, i don't know how to use this line "BRepAdaptor_Surface surface(TopoDS::Face(aMap(i)));"

Secondly, the fonction GetSurfaceProperties(), where it is define? I don't find it.

Sorry if my questions are stupid.

thx for advance,

Christian

Hi Christian (sorry for confusing your name/surname ;)

the sample code is taken from my application so let me explain:

- I used BRepLProp_SLProps to get the properties of a surface. To use that class I needed a BRepAdaptor_Surface object which is based on a TopoDS_Face taken from a map filled before

- GetSurfaceProperties looks something like this:

void shellDocObjectProperties::GetSurfaceProperties(double u, double v,
BRepLProp_SLProps & surfaceProperties,
BRepClass3d_SolidClassifier & solidClassifier,
ArrayList ^ output, SurfaceProperties propertyToCompute)
{
gp_Pnt point;
gp_Dir normal;

surfaceProperties.SetParameters(u, v);
point = surfaceProperties.Value();

//=======================
solidClassifier.Perform(point, Precision::Confusion());

//take only points that are on the surface of the object
if( solidClassifier.State() != TopAbs_ON)
{
return;
}
//=======================

output->Add(point.X());
output->Add(point.Y());
output->Add(point.Z());

switch (propertyToCompute)
{
case SurfaceProperties::CurvatureDirections:
{
gp_Dir minD, maxD;
surfaceProperties.CurvatureDirections(maxD, minD);

output->Add(minD.X());
output->Add(minD.Y());
output->Add(minD.Z());

output->Add(maxD.X());
output->Add(maxD.Y());
output->Add(maxD.Z());
}
break;

case SurfaceProperties::GaussianCurvature:
...
case SurfaceProperties::Normal:

This is how you can get the surface normal.

Hope this helps.

Commenter-1

Thank you for your help!!

I have some details to solve to do exactly what I want, but your help was very good !

Sorry for the late response and thx again.

With regards,

Christian

Dear Christian,

I face the same problem right now,would you share it!

Best Regards

Commenter-2