Get the zoom ratio of the viewport

Rhino Developer
1

Hello everyone!
Is there a way to get the zoom ratio of the viewport?
Or I want to know the distance from the camera to the world plane XY
（Suppose the camera is on top）
C++
Thanks!

1 Like
2

This isn’t C++, but it still might help you:

3

The world Z coordinate of the camera location is the distance from the world XY plane. Use absolute value if you want a positive distance for a location under the plane.

4

I found this one before, but it doesn’t seem to work. Zoom the view (middle mouse button), and its value is still the same.

  ON_3dPoint pt = doc->ActiveView()->ActiveViewport().VP().CameraLocation();
  double test = ON_Plane::World_xy.DistanceTo(pt);
  RhinoApp().Print(L"%f\n",test);

@davidcockey

5

Is my thinking wrong? I want to get the zoom value of the view.

6

Is the middle mouse button set for Zoom or ZoomLens? Zoom moves the camera. ZoomLens changes the focal length.

7

The Lens value does change.
doc->ActiveView()->ActiveViewport().VP().GetCamera35mmLensLength(&lens_Length);
However, the value of the focal length will vary according to the size of the subject.

8

Rhino viewports do not have a “zoom value.” Why do you need this?

Thanks,

– Dale

9

Thank you,Dale.
I want to determine whether the distance between two points is within a fixed screen coordinate distance.
Maybe I will convert these points to screen coordinates, and the calculation will be a bit simpler.

10

Yes, I would think so.

I have not tested this. But this should do it.

/// <summary>
/// Returns the screen distance, in pixels, between two 3D points.
/// </summary>
/// <param name="view">The view to evaluate the points.</param>
/// <param name="point0">The first 3D point.</param>
/// <param name="point1">The second 3D point.</param>
/// <returns>The screen distance in pixels.</returns>
static int RhScreenDistance(
  const CRhinoView& view, 
  ON_3dPoint point0, 
  ON_3dPoint point1
)
{
  ON_Xform world_to_screen;
  view.ActiveViewport().VP().GetXform(ON::world_cs, ON::screen_cs, world_to_screen);
  ON_2dPoint screen_point0 = world_to_screen * point0;
  ON_2dPoint screen_point1 = world_to_screen * point1;
  return (int)screen_point0.DistanceTo(screen_point1);
}

– Dale

2 Likes
11

It is perfect, thank you again sincerely!
:blush: