Get list of all Point3D in Viewport3D in WPF

Question

Is there a simple method to return a list of all Point3D present in a Viewport3D object in WPF? I need this collection in order to determine the XYZ bounds so that I can position the camera such that all Point3D are within the field of view.

If there is no simple method, which collections would I need to iterate over to ensure all Point3D are captured?

Answer 1

There is a very lengthy hierarchy we need to traverse to get to the data you want.

• Viewport3D.Children returns a Visual3DCollection object which contains a set of Visual3D

• Visual3D has 3 child classes; we are interested in ModelVisual3D

• ModelVisual3D.Children returns another Visual3DCollection ; you can clearly see the recursive tree structure with Viewport3D at the root

• ModelVisual3D.Visual3DModel returns a Model3D object

• Model3D has 3 child classes; we are interested in GeometryModel3D and Model3DGroup

• Model3DGroup.Children is another list of Model3D ; hence we have two layers of recursive containment

• GeometryModel3D.Geometry returns a Geometry3D object

• Curiously, Geometry3D only has one child class MeshGeometry3D

• MeshGeometry3D.Positions finally gives a raw list of points

---

Note that these points are in the local bases of their parent Geometry3D objects. In order to get the world coordinates, as you traverse the hierarchy you must accumulate a list of the transformations of any Model3D objects you encounter, and use them to transform the output points.

• Model3D.Transform returns a Transform3D object
• Transform3D has 3 child classes - AffineTransform3D , MatrixTransform3D and Transform3DGroup ; however we won't need to deal with them separately
• Transform3D.Transform(Point3D) is pretty self explanatory
• I don't see a multiplication operator between two Transform3D classes (except MatrixTransform3D ), so for each Point3D you must traverse the list of transformations in reverse order and apply each transformation in succession

---

The above summarizes why almost no one uses WPF for 3D development... a discussion which should be reserved for linux.stackexchange.com .