visualization of marine sand dune displacements utilizing modern gpu techniques. (franck michel)

VISUALIZATION OF MARINE SAND DUNE DISPLACEMENTS UTILIZING

MODERN GPU TECHNIQUES

Thomas Gierlingera,b, Andre R. Brodtkorbc, Andre Stumpfd,e, Marcel Weilera,b, Frank Michela,b

a) Fraunhofer IGD, Darmstadt, Germanyb) TU Darmstadt, Darmstadt, Germany

c) SINTEF ICT, Oslo, Norwayd) LDO, University of Western Brittany, Brest, France

e) IPGS, University of Strasbourg, Strasbourg, France

IQMULUS – BIG GEO DATA

• 4 year EU FP7 Research Project (8.1 Mio EUR)

• A High-volume Fusion and Analysis Platform for Geospatial Point Clouds, Coverages and Volumetric Data Sets

• IQmulus will leverage the information hidden in large heterogeneous geospatial data sets and make them a practical choice to support reliable decision making

• www.iqmulus.eu

Oct. 1st 2015 - GeoVIS Workshop @ ISPRS Geospatial Week 2015 - Frank Michel 2

SAND DUNE DISPLACEMENTS

Motivation

Detection of sand dune displacements by comparing bathymetricsurvey data from different points in time.

Submarine dunes and sand banks are among the most dynamic geomorphologic formations in coastal waters. Their movement can have significant impacts on the benthic ecosystem, marine transport in coastal waters, and infrastructure such as pipelines and communication cables.

Standard for the analysis of multi-temporal MBES surveys is visual analysis by trained experts delineating the crest line of the dunes at several time steps




Illustration of a manual analysis of two bathymetric surveys (Gómez et al., 2010)



The IQmulus Solution

Generate Locally Refined B-Splines• Continuous Surface Representation

Trim the surface to original extent

Sample the surface at selected resolution

• Regularly gridded DEM

Analyze using image correlation• Displacement fields


The IQmulus Solution

Generate Locally Refined B-Splines• Continuous Surface Representation

Trim the surface to original extent

Sample the surface at selectedresolution

• Regularly gridded DEM

Analyze using image correlation• Displacement fields


VISUALIZING LR B-SPLINES



The system approximates LR B-Splinesrepresenting the original point cloud

Check the accuracy of the approximated LR B-Splines

Display the LR B-Spline surface together with theoriginal point data

How to do this interactively?

Utilize modern GPU based methods!



But …

GPUs support only polygonal meshes• Convert the LR spline representation to a triangulation.

Uniform sampling of the surface will often either produce too many or too few triangles.

• Too many triangles will severely impact the interactivity • Too few triangles will dramatically reduce the quality

Use GPU hardware tesselator



• Extract Bezier coefficients of the LR B-Spline• Render patches of the LR B-Spline Surface• Generate triangles depending on the current view

• E.g. Screen space size of element• Tesselate the needed triangles on the GPU for each

rendered frame




• Review the approximated LR B-Spline Surface• Compare with whole input point cloud• Compare to outliers above a certain


• ddd


VISUALIZING DISPLACEMENT FIELDS



Chosen glyph for visualizing the displacement:

Visual attributes• Direction, Length, Color, Width

Can be mapped to different data attributes• Displacement direction, Displacement magnitude, etc.



How and when to visualize the glyphs?

Idea: Compute the visualization interactively on the GPU by accessing the original data.

Data available as GeoTIFF• Displacement X• Displacement Y• Uncertainty

Upload the original data to the GPU and use OpenGL Shader to evaluate data at needed positions.



How to generate glyph on the GPU?

Adjusting quality of Glyphs



As the generation is done on-the-fly (quality) parameterscan be changed interactively

• By the user (number, distribution and quality)• Depending on screen space size (quality)


VISUALIZING DISPLACEMANT FIELDS



• gg


CONCLUSION

Two approaches for interactive visualization of geospatialdata utilizing modern GPU based methods.

Analyzing intermediate and final results of a workflow tosupport the user in

• Inspecting approximation results (LR B-Splines)• Analyzing displacement fields (GPU glyphs)


THANKS

Co-Authors: Thomas Gierlinger, Andre R. Brodtkorb, Andre Stumpf, Marcel WeilerIQmulus project partners

You for your interest in our work!


Research leading to the results presented here is carried out within the project IQmulus(A High-volume Fusion and Analysis Platform for Geospatial Point Clouds, Coverages and Volumetric Data Sets) funded from the 7th Framework Programme of the European Commission, call identifier FP7-ICT-2011-8, under the grant agreement no. 318787, started in November 2012.

WANT TO KNOW MORE?

Today• Joint Poster Session

Tomorrow• GeoBigData @ Geospatial Week 2015• In this same room

• Project website: http://www.iqmulus.eu


visualization of marine sand dune displacements utilizing modern gpu techniques. (franck michel)

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