3D Model Maker lets you create virtual 3D models in your computer. You can create anything your imagination can think of. (Not limited to simple cubes or blocks like some apps!) It uses meshes of polygons just like they used in Toy Story. It uses the 3DS file format which is compatible with lots of professional software like Autodesk 3D Studio, Maya, AutoCAD and Blender.
It has not been updated for iPad in a long time, and it doesn't work on iOS 11