Proceedings: GI 2007

Fitted virtual shadow maps

Markus Giegl, Michael Wimmer

Proceedings of Graphics Interface 2007: Montréal, Québec, Canada, 28 - 30 May 2007, 159-168

DOI 10.1145/1268517.1268545

  • BibTex

    author = {Giegl, Markus and Wimmer, Michael},
    title = {Fitted virtual shadow maps},
    booktitle = {Proceedings of Graphics Interface 2007},
    series = {GI 2007},
    year = {2007},
    issn = {0713-5424},
    isbn = {978-1-56881-337-0},
    location = {Montr{\'e}al, Qu{\'e}bec, Canada},
    pages = {159--168},
    numpages = {10},
    doi = {10.1145/1268517.1268545},
    acmdoi = {10.1145/1268517.1268545},
    publisher = {Canadian Human-Computer Communications Society},
    address = {University of Waterloo, Waterloo, Ontario, Canada},


Too little shadow map resolution and resulting undersampling artifacts, perspective and projection aliasing, have long been a fundamental problem of shadowing scenes with shadow mapping. We present a new smart, real-time shadow mapping algorithm that virtually increases the resolution of the shadow map beyond the GPU hardware limit where needed. We first sample the scene from the eye-point on the GPU to get the needed shadow map resolution in different parts of the scene. We then process the resulting data on the CPU and finally arrive at a hierarchical grid structure, which we traverse in kd-tree fashion, shadowing the scene with shadow map tiles where needed. Shadow quality can be traded for speed through an intuitive parameter, with a homogenous quality reduction in the whole scene, down to normal shadow mapping. This allows the algorithm to be used on a wide range of hardware.