How to create 3d models for WPF?

I want to create a rectangle and set its perspective or use give it an elliptical appearance and use it at my Viewport3d.

How can I do this? And how can I create more complex shapes and define the texture area? 

Using Blend I could only do this writing the numeric values, but I have no idea if there's another way more productive.


Can you help me? 

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