How Raster to TIN (3D Analyst) works
The purpose of the Raster to TIN tool is to create a triangulated irregular network (TIN) whose surface does not deviate from the input raster by more than a specified Z tolerance. Raster to TIN is frequently used to convert a raster derived from a U.S. Geological Survey (USGS) digital elevation model (DEM) to a TIN surface model.
Raster to TIN first generates a candidate TIN using sufficient input raster points (cell centers) to fully cover the perimeter of the raster surface. It then incrementally improves the TIN surface until it meets the specified Z tolerance. It does so by adding more cell centers on an as-needed basis during an iterative process.
The interpolation zone of the input raster is honored in the output TIN. The polygonal representation of the interpolation zone is extracted from the raster, with z-values, and added as a soft clip polygon to the TIN.
The number of points selected by the command is a function of the specified Z tolerance and the smoothness of the input raster. If a small Z tolerance is specified or the raster surface is topographically rough and complex, more points will be required to build the TIN.
If specified, the maximum number of points acts as a TIN size constraint. The tool will stop and return a failure if the Z tolerance is not achieved by the time the node count of the TIN gets this big. This number is approximate, and it's possible to produce a TIN that is slightly larger than this value but it's recommended that TINs be kept under several million points. Large input rasters and small Z tolerance settings may exceed this. If size is an issue, consider processing subsets or use Raster To Multipoint followed by building a terrain dataset.
The Z factor is used to convert z-units (for example, feet to meters). The output TIN heights will be multiplied by this value to perform the conversion.
The Z tolerance is given in the z-units of the output TIN. For example, if the input raster z-units are in feet, and a Z factor of 0.3048 is used to convert them to meters in the output TIN, the Z tolerance should be specified in meters.