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Rendering Forest Scenes in Real-Time

Philippe Decaudin, Fabrice Neyret, Florent Cohen


Index

- Description
- Images, details and results
- rendering forest scenes in real-time with texcells
- dynamic lighting and shadowing
- Publications

Description

Note: A more general and recent approach for rendering semi-transparent and visually complex objects like trees in real-time is presented here.

Rendering forest scenes in real-time (2004)

This page describes a representation 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.

The 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.

No advanced graphics hardware feature is required 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.



Images, details and results

Rendering forest scenes

Cells and aperiodic tiling

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

    texcell (reference 3D-texture)

   They are mapped onto a surface
    regular mapping
    Preliminary results
      DivX (7.8 Mb)

    regular mapping regular mapping automn

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

    Texcells, aperiodic mapping

   Cells are rendered using slices

    parallel to the terrain for the simplest scheme
    texcells sliced parallel to the terrain

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

Video results

Cells:
.   max 128 slices of 256x256 textures ==> 12 Mb of compressed texture
.   20 trees / texture
Sequence #1:
.   ~2300 trees
.   570 cells with 4 trees / cell
.   ~30 fps on a P4 1.7GHz + GeForceFX 5800
Sequence #2:
.   ~37000 trees
.   9200 cells with 4 trees / cell
.   ~20 fps on a P4 1.7GHz + GeForceFX 5800
Video  Video

     DivX (34 Mb)

Dynamic lighting and shadowing

Per-pixel lighting

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

Shadowing

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

Video results

      DivX (14 Mb)



Related publications

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.




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