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Howto:Adding Cliffs To Terrain: Difference between revisions
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Added before/after images of cliffs
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This page describes how to use cliff information from OpenStreetMaps to improve the fidelity of terrain generated by TerraGear. | |||
==Why do cliffs require special treatment?== | ==Why do cliffs require special treatment?== | ||
Terrain generated from elevation data on a grid (e.g. Shuttle mission SRTM data) will tend to smooth out abrupt changes in height, such as cliffs. This is because each point on the grid records the average height in the region of the point, and TerraGear will, by default, smoothly interpolate between these points. So even if the grid elevation points were true point heights, the change in elevation is spread over the distance to the next grid point and cliffs become steep (or not-so-steep) slopes. The procedure below describes how to avoid these smoothing effects and properly texture the resulting near-vertical surfaces. | Terrain generated from elevation data on a grid (e.g. Shuttle mission SRTM data) will tend to smooth out abrupt changes in height, such as cliffs. This is because each point on the grid records the average height in the region of the point, and TerraGear will, by default, smoothly interpolate between these points. So even if the grid elevation points were true point heights, the change in elevation is spread over the distance to the next grid point and cliffs become steep (or not-so-steep) slopes. The procedure below describes how to avoid these smoothing effects and properly texture the resulting near-vertical surfaces. | ||
[[File:Sydney North Heads before including cliffs.png|thumb|North entrance to Sydney harbour constructed from SRTM-3 data without including information about cliff location.]] | |||
[[File:Sydney North Heads with cliffs included.png|thumb|North entrance to Sydney harbour constructed from SRTM-3 data after providing cliff location information to TerraGear.]] | |||
The following instructions assume that you are familiar with the [[TerraGear]] toolchain, extracting data from OpenStreetMaps, and creating shapefiles. In the commands below, <code><scenery_top></code> refers to a directory with a conventional layout for scenery construction, that is, containing shapefile and height data in <code>data</code>, intermediate files in <code>work</code>, and output in <code>output</code>. Other files are placed in <code>scenery_top/rawdata</code> | The following instructions assume that you are familiar with the [[TerraGear]] toolchain, extracting data from OpenStreetMaps, and creating shapefiles. In the commands below, <code><scenery_top></code> refers to a directory with a conventional layout for scenery construction, that is, containing shapefile and height data in <code>data</code>, intermediate files in <code>work</code>, and output in <code>output</code>. Other files are placed in <code>scenery_top/rawdata</code> | ||