Terrain data can often come in the form of a GeoTIFF. This is a gridded height map that will import directly into Muk3D as a grid. Sometimes these GeoTIFFs can be very large (of the order of Gigabytes of data, billions of grid points). We can't work with these for modelling, but there are some easy ways to get the data into Muk3D and turn it into something that we can use.
The first thing we want to do is get the grid loaded just to look at the data. We do this be resampling the grid, rather than trying to load everything. There are 2 ways to do this:
- Using Import GeoTIFF, and set the sample size to be 'large'.
- Use Resize georeferenced image and reduce it to a fraction of the heightmap size.
Resize georeferenced image will generally be faster than Import GeoTIFF especially for grids with more than a few million points. For example, a 2Gb TIFF with 2.5 billion points took around 2 minutes and required about 10 Gb of ram to process using Import GeoTIFF. The same dataset took approximately 2 seconds to process using Resize georeferenced image.
Once we can see the data, we can decide if we need to work with the entire tile, or just a part of it. If its just a part of the grid we want to work with we have 2 methods for extracting the relevant section:
If the grid was loaded at the user required resolution, then use Grid/Create/Extract from existing grid to draw a rectangle around the section to work with. This will create a new grid layer with the sub-grid.
If the grid loaded is at a lower resolution than desired and the grid can't be loaded at the desired resolution, then you can use Tex/Import/Extract from georeferenced image. This command requires a boundary to use to define the region to extract. If you don't already have one, you can draw one using the resampled grid imported above. Draw a line or rectangle to define the area, save it, and then use it in the Extract from georeferenced image command.
On the dialog for Extract from georeferenced image, there is a checkbox to treat the image as a multi-band image. A geotiff will have a single band so this checkbox needs to be unchecked.
It is also important that the output file name has .tif at the end of it. If it doesn't then a Jpeg will be created which is unsuitable for use as a height map.
- Data import/GeoTIFF/Inspect GeoTIFF
- Data import/GeoTIFF/Import GeoTIFF
- Grid/Create/Extract from existing grid
- Tex/Import/Resize georeferenced image
- Tex/Import/Extract from georeferenced image
Extract from georeferenced image fails with an error message. Make sure that the Multiband is unchecked.
Extract from georeferenced image creates a Jpeg. Make sure that the output file name has .tif at the end of it so a GeoTIFF is created.