Interactive Non-Photorealistic Modeling
Bachelor project by Niels van der Kaap
Non-Photorealistic Rendering (NPR) is a branch of computer graphics that focuses on rendering models in a non-real way for a particular reason, for example, to stress certain details of a model or to create a comic figure from a real photo. The result is that modeling increases to become an artists job instead of that of a computer specialist.
A problem that arises due to this development is that most three dimensional modeling tools are still written from a programmers perspective: knowledge on triangular meshes is usually required to be able to start modeling. The solution for this problem is the introduction of a new class of modelers that makes the task feel more natural: creating a 3D model should be as easy as sketching an image on paper.
In this project, a natural modeler was developed that can be used for editing existing 3D models. After a model is loaded the input of the program consists of pen strokes, creating by dragging the mouse while holding the left mouse button. An algorithm then determines the type of operations that should be performed: either selection or bending. Selection occurs when a loop was drawn. In that case, the part inside the loop is selected. Selection operations can be repeated multiple times, to refine the area that the user wants to apply bending to.
Once the right part of the model is selected, it can be bent by a spine algorithm. This algorithm requires two input input 'pen strokes', that represent the spine before and afterwards respectively. It works by first determining the location on the first spine for each mesh point in the model, and then calculating its position with respect to the new spine.