Computer Graphics and Multimedia Systems, University of Siegen, Germany 1 GPU-Based Responsive Grass...
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Computer Graphics and Multimedia Systems, University of Siegen, Germany
1
GPU-Based Responsive GrassGPU-Based Responsive GrassJens Orthmann, Christof Rezk-Salama, Andreas Kolb
Computer Graphics and Multimedia Systems, University of Siegen, Germany
2OverviewOverview
Motivation
Grass Representation
Collision Handling
Rendering
Results
Future Work
Computer Graphics and Multimedia Systems, University of Siegen, Germany
3MotivationMotivation
Physically correct reacting environment improves immersion for players
Until now: research has been focused on the animation and rendering
Modern graphics cards shift the workload to the GPU
Computer Graphics and Multimedia Systems, University of Siegen, Germany
4Grass BillboardsGrass Billboards
Usually: Clumps of grass are approximated by billboards quad with a semi-transparent texture
Crossed billboards produce a more volumetric impression
Computer Graphics and Multimedia Systems, University of Siegen, Germany
5CPU-Based PredecisionCPU-Based Predecision
The grass layer is organized in an octree
A lookup into the octree brings up colliding nodes
Affected billboards will be handled on the GPU
Computer Graphics and Multimedia Systems, University of Siegen, Germany
6GPU-Based CollisionhandlingGPU-Based Collisionhandling
Collision detection and reaction requires a more detailed mesh
Collisions are detected and resolved per vertex
Mass-spring system preserves the shape
Performance stability via recovering
Animation +Refinement
Collision-detection
Collision-reaction
Recovering Simplification
Computer Graphics and Multimedia Systems, University of Siegen, Germany
7Depth CubesDepth Cubes
Objects are implictly represented by depth-cubes
The mesh is projected to each face
Each face stores the distance to the surface and the normal information
Computer Graphics and Multimedia Systems, University of Siegen, Germany
8Collision DetectionCollision Detection
Vertex collides if it is occluded by all six faces of the depth cube
Occlusion is determined by a lookup within the depth cube
The accuracy of the detection depends on the resolution of the depth cube
Computer Graphics and Multimedia Systems, University of Siegen, Germany
9Collision ReactionCollision Reaction
The normal vector within the depth cube defines the reaction‘s direction
The vertex then is moved along the normal out of the object
As each vertex is handled separately unrealistic distortions may occur
Computer Graphics and Multimedia Systems, University of Siegen, Germany
10Shape PreservationShape Preservation
Spring model preserves the overall shape
Topology information is required
Length constraints correct adjacent vertices
Computer Graphics and Multimedia Systems, University of Siegen, Germany
11RecoveringRecovering
Previously collided billboards will regenerate
Interpolation between deformed and undeformed shape
Billboards will be simplified after regeneration
deformedundeformed
Computer Graphics and Multimedia Systems, University of Siegen, Germany
12Irradiance InformationIrradiance Information
Ambient occlusion: How much light reaches a point and from which direction?
Amount and mean-direction are determined by using shadow maps
Sampling an environment map results in the irradiance
Computer Graphics and Multimedia Systems, University of Siegen, Germany
13RenderingRendering
Irradiance information is precomputed for the complete grass layer
During runtime: tri-linear interpolation within the volume results in the irradiance
Computer Graphics and Multimedia Systems, University of Siegen, Germany
14Alpha-To-CoverageAlpha-To-Coverage
The transparency of a pixel determines how much sub-samples are colored
The final color is calculated during the multi-sample resolve phase
Quality depends on the multi-sampling resolution
Computer Graphics and Multimedia Systems, University of Siegen, Germany
15ResultsResults
Video
Computer Graphics and Multimedia Systems, University of Siegen, Germany
16Future WorkFuture Work
Take dynamic environments one step further
Enables integration of new game elements and extends game logics
Apply responsive grass algorithm to small plants like bushes, shrubs…
Improvement of visual results by dynamic sub-divisions
Computer Graphics and Multimedia Systems, University of Siegen, Germany
Thank YouThank You
Thank you for your attention
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