3.4 Using dsm2tif to Visualize DSMs

dsm2tif is a utility to convert 3Delight's proprietary deep shadow map files into viewable TIFF files. A DSM contains visibility data for any given depth in a scene, so one single 2D image (e.g. a TIFF) cannot describe all the information provided by a DSM; that is why command line parameters are provided to specify at which depth the evaluation occurs.

` -z depth'

Specifies a relative depth at which the deep shadow map is evaluated. "Relative" means that each pixel in the image is evaluated at its own depth. It is computed as follows: (pZmax-pZmin) * depth + pZmin. pZmin and pZmax being the depths of the closest and the furthest features present in the pixel. `-z 1' is the default, which shows the amount of light that passes through to infinity at each pixel.

` -Z depth'

Specifies an absolute depth (range: [0..1]) to evaluate the deep shadow map. "Absolute" means that all pixels in the output image are evaluated at the same depth, computed as follows: (Zmax-Zmin) * depth + Zmin. Zmin and Zmax being the depths of the closest and the furthest features in the DSM.

` -bias n'

Specifies a shadow bias for deep shadow map evaluation. This is needed to avoid self-occlusion problems. If the produced TIFF contains noisy areas, consider increasing this parameter. Default is 0.015.

` -opacity'

By default, dsm2tif assigns a "visibility" value to each pixel in the output TIFF, specifying this option assigns "opacity" values to each pixel (opacity = 1-visibility). This means that dark areas in the image indicate that light passes through unnoccluded.

` -mipmap n'

This options specifies which mipmap level is converted. Note that mipmapping can be disabled by an option given to the display driver (see section The DSM display driver).

` -8'

` -16'

` -32'

` -float'

Chooses data format for the output TIFF. Default is 8 bits per channel.

` -lzw'

` -deflate'

` -packbits'

` -logluv'

Selects a compression scheme. Default is `lzw'. `-logluv' is only supported with `-float' data type.

` -v'

Prints version and copyright information.

` -h'

Shows help text.

3Delight 10.0. Copyright 2000-2011 The 3Delight Team. All Rights Reserved.