Rendering Forest Scenes in Real-TimeRendering Forest Scenes in Real-Time

EGSR 2004EGSR 2004

Philippe Decaudin Fabrice NeyretPhilippe Decaudin Fabrice Neyret GRAVIR/IMAG-INRIA, Grenoble, FranceGRAVIR/IMAG-INRIA, Grenoble, France

2 Rendering Forest Scenes in Real-Time EGSR 2004

Rendering Forest Scenes in Real-Time:Rendering Forest Scenes in Real-Time:Previous workPrevious work

BillboardsBillboards Textured quad facing camera,Textured quad facing camera,

or crossor cross Widely used by applicationsWidely used by applications

Flight simulators, Games, … Flight simulators, Games, … + efficiency+ efficiency- no parallax, popping- no parallax, popping

Simplified textured treesSimplified textured trees+ parallax, 3D consistency+ parallax, 3D consistency- more expensive- more expensive

3 Rendering Forest Scenes in Real-Time EGSR 2004

Rendering Forest Scenes in Real-Time:Rendering Forest Scenes in Real-Time:Previous workPrevious work PointsPoints

Objects = distribution of discsObjects = distribution of discs[Levoy, Whitted - 85][Levoy, Whitted - 85][Pfister et al - SIG’00] [Rusinkiewicz et al - SIG’00][Pfister et al - SIG’00] [Rusinkiewicz et al - SIG’00][Stamminger, Drettakis - EWR’01] [Dachsbacher et al - SIG’03][Stamminger, Drettakis - EWR’01] [Dachsbacher et al - SIG’03]……

+ adaptive+ adaptive - aliasing- aliasing(-) cost = 1 transformed vertex / point (-) cost = 1 transformed vertex / point

[Stamminger Drettakis 01][Stamminger Drettakis 01]

4 Rendering Forest Scenes in Real-Time EGSR 2004

Rendering Forest Scenes in Real-Time:Rendering Forest Scenes in Real-Time:Previous workPrevious work

Volumetric texturesVolumetric textures Volumetric densities to represent fuzzy material Volumetric densities to represent fuzzy material

[Kajiya, Kay - SIG’89][Kajiya, Kay - SIG’89][Neyret - GI’95[Neyret - GI’95TVCG’98]TVCG’98][Meyer, Neyret - EWR’98][Meyer, Neyret - EWR’98][Lengyel et al - EWR’01][Lengyel et al - EWR’01]……

+ few polygons, more textures+ few polygons, more textures+ easy to filter+ easy to filter- repetitive tiling- repetitive tiling- slicing might be visible- slicing might be visible

pattern

5 Rendering Forest Scenes in Real-Time EGSR 2004

Our approachOur approach

Goal:Goal: Render dense forests Render dense forests In real-timeIn real-time With good visual qualityWith good visual quality Smooth during a flyoverSmooth during a flyover

Assumption: forests are viewed from a distanceAssumption: forests are viewed from a distance

Approach: improved real-time volumetric texturesApproach: improved real-time volumetric textures1.1. Avoid pattern mapping repetitionAvoid pattern mapping repetition

2.2. Avoid view dependant artifactsAvoid view dependant artifacts

3.3. Adapted to the distanceAdapted to the distance

6 Rendering Forest Scenes in Real-Time EGSR 2004

1. Making volumetric texture aperiodic1. Making volumetric texture aperiodic

Avoids repetitivityAvoids repetitivity Requires a set of edge-compatible patternsRequires a set of edge-compatible patterns

Aperiodic mappingAperiodic mapping

[Stam - 97] [Neyret, Cani - SIG’99] [Cohen et al - SIG’03][Stam - 97] [Neyret, Cani - SIG’99] [Cohen et al - SIG’03]

7 Rendering Forest Scenes in Real-Time EGSR 2004

1. Making volumetric texture aperiodic1. Making volumetric texture aperiodic

Storing the patternsStoring the patterns

Hardware friendlyHardware friendly

+ one texture+ one texture

+ wrap+ wrap

+ compliant with+ compliant withmin and mag filteringmin and mag filtering

v

u

8 Rendering Forest Scenes in Real-Time EGSR 2004

1. Making volumetric texture aperiodic1. Making volumetric texture aperiodic

Shape of a forest pattern: a prismShape of a forest pattern: a prism

We build a set of edge-compatible prisms,We build a set of edge-compatible prisms,

that we call that we call TexcellsTexcells

9 Rendering Forest Scenes in Real-Time EGSR 2004

2. Our slicing scheme2. Our slicing scheme

Volumetric data cannot be rendered directly by GPUVolumetric data cannot be rendered directly by GPU Rendered using textured slicesRendered using textured slices The simplest slicing scheme:The simplest slicing scheme:

Slices parallel to the terrainSlices parallel to the terrain

But suffer from artifacts…But suffer from artifacts…

SlicesTerrain

Texcell

10 Rendering Forest Scenes in Real-Time EGSR 2004

2. Our slicing scheme2. Our slicing scheme

Slices parallel to the terrain : artifactsSlices parallel to the terrain : artifacts

Slicing is Slicing is visible at visible at

grazing anglesgrazing angles

Too Too transparenttransparent

Too blurredToo blurred

Silhouette Silhouette texcellstexcells

Opacity Opacity adjustmentadjustment

Anisotropic Anisotropic filteringfiltering

LODLOD

11 Rendering Forest Scenes in Real-Time EGSR 2004

2. Our slicing scheme2. Our slicing scheme

2 kinds of texcells2 kinds of texcells

RegularRegular texcells texcells Sliced parallel to the groundSliced parallel to the ground

Set of 2D texturesSet of 2D textures Good quality and efficiencyGood quality and efficiency

except at the silhouetteexcept at the silhouette

SilhouetteSilhouette texcells texcells Sliced "parallel" to the screenSliced "parallel" to the screen

3D texture3D texture More expensive usedMore expensive used

near the landscape silhouettenear the landscape silhouette

12 Rendering Forest Scenes in Real-Time EGSR 2004

2. Our slicing scheme: silhouette texcells2. Our slicing scheme: silhouette texcells

Tilting the slicesTilting the slices Vertices are moved vertically, no new vertices are createdVertices are moved vertically, no new vertices are created Can be done by a vertex programCan be done by a vertex program

13 Rendering Forest Scenes in Real-Time EGSR 2004

3. LOD scheme3. LOD scheme

For regular texcellsFor regular texcells Texture set: 2D textures + MIP-mapTexture set: 2D textures + MIP-map

For silhouette texcellsFor silhouette texcells We fit the slicing rate to the MIP-map level of the 3D textureWe fit the slicing rate to the MIP-map level of the 3D texture

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ResultsResults Texcells:Texcells:

128 slices of 256x256 textures128 slices of 256x256 textures 12 Mb of compressed texture 12 Mb of compressed texture

20 trees / texture20 trees / texture Aperiodically mappedAperiodically mapped

ShadingShading precomputed and stored in the texturesprecomputed and stored in the textures + pseudo-shading corresponding to the lighting of the terrain+ pseudo-shading corresponding to the lighting of the terrain

15 Rendering Forest Scenes in Real-Time EGSR 2004

ResultsResults

Seq #1Seq #1 ~2300 trees ~2300 trees 570 texcells570 texcells

with 4 trees/texcellwith 4 trees/texcell ~30 fps 640x480~30 fps 640x480

(P4 1.7GHz, (P4 1.7GHz, GeForceFX 5800)GeForceFX 5800)

Seq #2Seq #2 ~37000 trees ~37000 trees 9200 texcells9200 texcells

with 4 trees/texcellwith 4 trees/texcell ~20 fps 640x480~20 fps 640x480

(P4 1.7GHz,(P4 1.7GHz,GeForceFX 5800)GeForceFX 5800)

16 Rendering Forest Scenes in Real-Time EGSR 2004

Conclusion & future workConclusion & future work A scheme for quality real-time volumetric texturesA scheme for quality real-time volumetric textures Coupled with an aperiodic mapping schemeCoupled with an aperiodic mapping scheme Correct filtering of the volumetric dataCorrect filtering of the volumetric data Full parallax effectsFull parallax effects Well suited to represent and render dense forestsWell suited to represent and render dense forests Texcells can be mixed with other representationsTexcells can be mixed with other representations

Future workFuture work Better cullingBetter culling Dynamic lighting and shadowingDynamic lighting and shadowing

[Poster at Siggraph 2004][Poster at Siggraph 2004] Maximize the use of the GPUMaximize the use of the GPU