Rendering Forest Scenes in Real-Time
Texcells

Rendering forest scenes in real-time (2004)

We propose a new representation, called texcell, allowing for the real-time rendering of realistic forests covering an arbitrary terrain. It lets us produce dense forests corresponding to continuous non-repetitive fields made of thousands of trees with full parallax.

Our representation draws on volumetric textures and aperiodic tiling: the forest consists of a set of edge-compatible prisms containing forest samples which are aperiodically mapped onto the ground. The representation allows for quality rendering, thanks to appropriate 3D non-linear filtering. It relies on LODs and on a GPU-friendly structure to achieve real-time performance.

We require no advanced graphics feature except 3D textures and decent fill and vertex transform rates. However we can take advantage of vertex shaders so that the slicing of the volumetric texture is entirely done on the GPU.

More details in this Paper.

GPU-Based Lighting and Shadowing of Complex Natural Scenes (2004)

Lightings and shadows are essential elements toward realism of landscapes (e.g., terrain, vegetation, or any complex shapes bounded in a layer above a surface) because they help understanding shapes. However:

- Using polygonal meshes and classical shadowing algorithms are too costly in terms of computation for complex scenes;
- Adapted algorithms for dedicated representations such height-fields are efficient, but these representations are too limited for our needs (e.g. forest);
- Although more powerful representations like surfels or texels exist, algorithms for quality and efficient lighting and shadowing are not available yet.

Thus, our goal is to propose lighting and shadowing techniques adapted to such representations as well as the GPU.

More details in this Presentation.

Rendering forest scenes with texcells

•   Texcells are prisms containing a forest sample and stored in a 3D texture (or a set of 2D textures)

    

•   They are mapped onto a surface

         
    Preliminary results (7.8 Mb, DivX)

    

•   Aperidic tiling is used to avoid repetitiveness;
    in the following examples, 8 reference edge-compatible texcells are patched together

    

•   Texcells are rendered using slices

    parallel to the terrain for the simplest scheme
    

    mixed with slices parallel to the screen near the landscape silhouette, and a LOD (level of details) scheme
    
    
    

Video  (34 Mb, DivX)

Dynamic lighting and shadowing

    We use an adapted form of the Lafortune lighting model;
    evaluation is done using the GPU
    

    We extend the horizon-mapping technique;
    several horizon-maps are pre-computed at different heights above the surface
    

    GPU based per-pixel lighting and shadowing of texcells (14 Mb, DivX)

- Ph. Decaudin, F. Neyret. Rendering Forest Scenes in Real-Time. Rendering Techniques '04 (Eurographics Symposium on Rendering), Norrköping, Sweden , p 93--102, June 2004.

- F. Cohen, Ph. Decaudin, F. Neyret. GPU-Based Lighting and Shadowing of Complex Natural Scenes. Siggraph'04 Poster (Conf. DVD-ROM), Los Angeles, USA, August 2004.

-  A. Meyer, Ph. Decaudin, F. Neyret. Représentations Alternatives (in french). Informatique Graphique et Rendu, chapter 8 (Traité IC2, série traitement du signal et de l'image). Hermes Science Publications, ISBN 978-2-7462-1515-3, March 2007.

- My other publications.