Translating two-dimensional user input on three-dimensional scene

A computing system translates two-dimensional (2D) graphical input by a user who is selecting one or more 2D images in a three-dimensional (3D) scene of 3D models created by model 3D objects. The computing system comprises a viewport module, a retrieve module, set ray module and, a hit detection module. The viewport module defines 2D boundaries of the 3D scene and a view point location in 3D space for viewing the 3D scene. The retrieve module retrievies a selection point location in 2D space for the 2D graphical input. The set ray module sets a pick ray in 3D space based on the view point location and the selection point location. The hit detection module detects a hit by the pick ray on a 3D model in the 3D scene. In this computing system there is a method of processing a hierarchy of computer program visual objects for detecting a hit by 2D input on 2D and 3D images displayed by a computing system. The method begins by traversing branches of a first tree hierarchy of visual objects to leaf objects. Next the method detects whether the next unprocessed leaf object is a visual 2D object with 2D geometry or a model 3D object with 3D geometry. Lastly the method calls a 2D process to detect a hit on the 2D geometry of a visual object if a visual 2D object is detected and calls the 3D process to detect a hit on the 3D geometry of a visual object if a model 3D object is detected.