StandardTransform3D Class

Because WPF does not allow deriving your own classes from Transform3D object, it is not possible to create our own class that could be set to the Model3D.Transform or Visual3D.Transform property. This means that you cannot use something like:

model3d.Transform = new StandardTransform3D(); // not possible

Instead the usage patter for StandardTransform3D is to use its static StandardTransform3D.SetStandardTransform3D method to assign the StandardTransform3D to Model3D or Visual3D. Behind the scenes the method adds a StandardTransform3D.StandardTransform3DProperty to the Model3D or Visual3D. This way we store the StandardTransform3D to the object that is using it and this way we can read the assigned StandardTransform3D by using the static StandardTransform3D.GetStandardTransform3D method.

The SetStandardTransform3D by default (default value of updateTransform3D attribute is true) also sets the Transform property of the Model3D or Visual3D to the StandardTransform3D.Transform property. This property is a MatrixTransform3D that is created based on the translate, rotate and scale transform.

When the properties of StandardTransform3D change, then this also updates the MatrixTransform3D.

The class also implements BeginInit and EndInit to update the matrix only once even when multiple properties are changed.

Usage example:

var standardTransform3D = new StandardTransform3D()
{
    RotateY = 30,
    TranslateX = 100
};

// Assign standardTransform3D to model3d.Transform and store it in the model3d object
StandardTransform3D.SetStandardTransform3D(model3d, standardTransform3D); 

// ...

// Change rotation:
standardTransform3D.RotateY += 10; // This will update the MatrixTransform3D (standardTransform3D.Transform) and also the model3d because its Transform is set to the same MatrixTransform3D.

// ...

// Somewhere else in the application we can read the StandardTransform3D from a Model3D or Visual3D:
var standardTransform3D = StandardTransform3D.GetStandardTransform3D(model3);

Reference