Holocene Evolution, OFR 01-076

ANIMATION

Visualization

The culmination of the GIS work is enabling the data to be used as a visualization tool to explain and illustrate large-scale geologic processes in the CRLC to both scientists and the non-scientific community. Besides the usefulness of the data in the GIS, these data were also used to create an animation of the Holocene coastal evolution.

How the Animation was Created

Once the individual surfaces for each 1000-year time step were completed and merged with the modern DEM, these grids were then exported as X, Y, Z ascii files. These files were then regridded using the SwathEditor Toolkit software from University of New Brunswick Ocean Mapping Group (URL: http://www.omg.unb.ca/~jhc/SwathEd.HTMl). This gridding step was performed primarily to convert the X,Y, Z file into an OMG/R4 grid format which is easily imported into Interactive Visualization Systems (URL: http://www.ivs.unb.ca) software package Fledermaus. Both the SwathEditor Toolkit and Fledermaus were running on a Silicon Graphics computer system. For greater flexibility in creating colormaps for the grids, the seaward and landward portion of each surface was exported from ArcView as a separate file. Once a satisfactory colormap for each portion of the surface was created in Fledermaus, the two grids were seamlessly displayed together for the fly-throughs.

Using a 3d mouse a flight path over the study area was created and saved. Once this flight path was saved, individual frames were rendered for each 3d surface using Fledermaus´ movieclient tool. These series of images were saved for all 12 surfaces (11,000 yr BP to present day). Because the images follow the same sequence for each surface, it was easy to select which images from each time frame needed to be used for the animation at a particular location. This technique allowed the animation to not only fly through space, but to fly through space and time simultaneously. Once the selection of more than 2300 images was made, some indication of the time frame represented by the surfaces was necessary. A simple time bar was created with a red bar indicating the time frame being displayed. This time bar tiff image file was merged with the appropriate 3d image using the "merge" command on a Linux computer. The final step in creating the animation was to actually combine all 2377 tiff images into a single mpeg animation file. This final step was accomplished with the shareware software package VideoMach.

What the Animation Shows

The initial part of the animation flies over the modern day surface down the Columbia River and out to sea. Then turns around to look back at the shore. Once offshore, the animation pauses and while remaining in a stationary place, the images begin to step back through time in 1000 year increments. The time bar that now appears in the lower left corner of the image indicates which time frame is being viewed. Present day has a white time bar, 1,000 yr BP has one red rectangle, 2,000 yr BP two red rectangles and so forth through to 11,000 yr BP.

Once the image of 11,000 yr BP is reached, then flight begins again. This time flight will take place through space and time simultaneously. The flight circles to the southern end of the study area and then moves north along the coast. The time frame of the images now goes from the most distant past (11,000 yr BP) to the present in 1,000-year time steps. Once the present day is reached, the animation pauses, then begins to zoom out so that the whole present day coastline of the study area is visible.

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