Project to Plane in a Specified Direction

Hi all,

I want to project curves onto a plane in a specified direction using rhinoCommon. As far as I understand the ProjectToPlane method has no input for projection direction:

ProjectToPlane(curve: Curve, plane: Plane) -> Curve

A possible work around is to make a big enough planar surface and then use ProjectToBrep but I wonder if there is a better way?

I know that David added a Grasshopper component that already does this but as I said I want to do it inside the scripting component.

Thanks,

Mostapha

Replies to This Discussion

Permalink Reply by Jesus Galvez on September 6, 2013 at 3:31pm

I usually check to see how rhinoscriptsyntax does things to get an understanding of how Rhinocommon's methods work. There is no ProjectToPlane command in rhinoscritpsyntax, but there is a ProjectToSurface. It should be similar.

It's at line 2309.

Permalink Reply by Mostapha Sadeghipour Roudsari on September 6, 2013 at 7:30pm

Hi Jesus,

Thank you for the reply. As you can see in line 2324 script uses ProjectToBrep method which is the work around that I mentioned.

newcurves = Rhino.Geometry.Curve.ProjectToBrep(curves, breps, direction, tolerance)

To do this I need to generate the surface each time based on the plane that I want to avoid if possible.

Permalink Reply by Mateusz Zwierzycki on September 6, 2013 at 10:59pm

Yea, this method is quite problematic. Try this http://www.grasshopper3d.com/forum/topics/about-oblique-projection-...

Permalink Reply by Mostapha Sadeghipour Roudsari on September 8, 2013 at 9:07am

Awesome! This is exactly what I was looking for...Thanks Mateusz! :)

Permalink Reply by Pieter Segeren on November 19, 2014 at 3:54am

Hi guys, does anybody have this info saved? The page that Mateusz refers to is gone...

Permalink Reply by Arend on November 19, 2014 at 9:09am

Given a curve (or any geometry that is derived from GeometryBase, and possibly others too)

you can project a single curve like this:

yourCrv.Transform(Rhino.Geometry.Transform.PlanarProjection(yourPlane))

Permalink Reply by Mostapha Sadeghipour Roudsari on November 19, 2014 at 9:16am

I haven't tested Arend's suggestion and if that works it is much more elegant from the function that I wrote:

https://github.com/mostaphaRoudsari/ladybug/blob/master/src/Ladybug...

Permalink Reply by Pieter Segeren on November 19, 2014 at 11:17am

Hi Mostapha, thanks for the link to your approach. Arend's method is a planar projection, so I'll try and translate this python script.
Seems like a challenge, let's see what happens..:)
Thanks again.

Permalink Reply by Arend on November 19, 2014 at 11:27am

Hmm. Not too sure how to create that transformation matrix, but it should certainly be possible:

What you're looking for is called an oblique projection, (see http://en.wikipedia.org/wiki/Oblique_projection and http://www.slideshare.net/SanuPhilip/projection-in-computer-graphics )

Permalink Reply by Pieter Segeren on November 19, 2014 at 11:52am

Yes, I read that in the link Mateusz posted, hence my curiousness, but unfortunately the page is gone. Let me see what I can get from your links, thanks for that.

Permalink Reply by Arend on November 20, 2014 at 3:33am

I gave it a little try - I think it worked quite well.
The transformation matrix is solved here by using the plane equation and the direction vector, creating a rhinocommon transformation matrix seemed to work quite well:





  /**
  See: http://stackoverflow.com/questions/2500499/howto-project-a-planar-p...
  1-a*dx/D    -b*dx/D    -c*dx/D   -d*dx/D
  -a*dy/D   1-b*dy/D    -c*dy/D   -d*dy/D
  -a*dz/D    -b*dz/D   1-c*dz/D   -d*dz/D
  0          0          0         1
  */
  public Transform GetObliqueTransformation(Plane Pln, Vector3d V)
  {
    Transform oblique = new Transform(1);
    double[] eq = Pln.GetPlaneEquation();
    double a,b,c,d, dx, dy, dz, D;
    a = eq[0];
    b = eq[1];
    c = eq[2];
    d = eq[3];
    dx = V.X;
    dy = V.Y;
    dz = V.Z;
    D = a * dx + b * dy + c * dz;
    oblique.M00 = 1 - a * dx / D;
    oblique.M01 = -a * dy / D;
    oblique.M02 = -a * dz / D;
    oblique.M03 = 0;
    oblique.M10 = -b * dx / D;
    oblique.M11 = 1 - b * dy / D;
    oblique.M12 = -b * dz / D;
    oblique.M13 = 0;
    oblique.M20 = -c * dx / D;
    oblique.M21 = -c * dy / D;
    oblique.M22 = 1 - c * dz / D;
    oblique.M23 = 0;
    oblique.M30 = -d * dx / D;
    oblique.M31 = -d * dy / D;
    oblique.M32 = -d * dz / D;
    oblique.M33 = 1;
    oblique = oblique.Transpose();
    return oblique;
  }

Attachments:

oblique transformation.gh, 11 KB

Permalink Reply by Pieter Segeren on November 20, 2014 at 5:07am

Thanks Arend :)
I was going to try to prepend a shear transformation to your earlier ProjectPlanar script (I read somewhere "Oblique projection = Shear + Orthogonal projection"), but I haven't had the time to do so. Will be after this weekend before I can try that.

Thanks for your contibution Arend, unfortunately your code yields a CS1061 error over here:
Rhino.Geometry.Transform bevat geen definitie voor Transpose en er is geen extenstemethode Transpose gevonden waarmee het eerste argument van het type Rhino.Geometry.Transform wordt geaccepteerd (mogelijk ontbreekt er een gebruiksinstructie of een assembly-verwijzig)(line 116).

I'll get back to you after the weekend. Ik ga effe uitwaaien op Texel:)