Graphics Reference
In-Depth Information
2
III
Screen-Space Deformable
Meshes via CSG with
Per-Pixel Linked Lists
Joao Raza and Gustavo Nunes
2.1 Introduction
In this chapter we describe a deformable mesh method that utilizes an implemen-
tation of the Constructive Solid Geometry (CSG) algorithm in real time through
the usage of a per-pixel linked list data structure stored in the GPU memory. Via
this method, the proposed CSG algorithm manages to have a constant number
of passes. This contrasts with standard image-based CSG implementations in
which the number of required rendering passes increases linearly with the scene's
depth complexity.
Although the union, intersection and difference CSG operations can be ren-
dered via this approach, this chapter focuses on the difference operation, since
it yields a deformable mesh scenario. Moreover, a modification to the CSG al-
gorithm behavior is made in a particular case to properly target the deformable
mesh scenario. The solution presented here is generic, does not make any as-
sumption on the scene's topology, and works for any concave, convex, or flat
mesh.
2.2 Mesh Deformation Scenario
Games and real-time applications utilize deformable meshes as a mechanism for
enhancing the user experience and providing immediate feedback to their actions.
Common scenarios are for deforming car models when they hit obstacles, or al-
tering walls as explosions impact them. Mechanisms to enable mesh deformation
vary from altering the vertices in the mesh structure to utilizing parallax map-
ping. Although these algorithms succeed in presenting a deformable mesh to the
 
 
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