GeneratePlyFile¶

Generate a 3D Ply file from a DEM and a color image.

Description¶

The application converts an image containing elevations into a PLY file, which is a file format to store 3D models. This format is adpated for visualization on software such as MeshLab [2] or CloudCompare [3]

This application is part of the stereo reconstruction framework. The input data can be produced by the application DisparityMapToElevationMap.

There are two types of supported input images:

A DEM image, with a ground projection, containing elevation values. Each elevation value can be considered as a 3D point.
A 3D grid image, containing 5 bands (the first 3 are the 3D coordinates of each point, the 5th is a validity mask where valid values are larger or equal to 1)

The user shall also give a support image that contains color values for each 3D point. The color values will be embedded in the PLY file.

Parameters¶

The input DEM image -indem image Mandatory
The image should be either a projected DEM or a 3D grid containing 3D point coordinates and a validity mask.

Conversion Mode -mode [dem|3dgrid] Default value: dem

DEM
DEM conversion mode (the projection information of the DEM is used to derive the X and Y coordinates of each point)
3D grid
3D grid conversion mode

Map Projection -map [utm|lambert2|lambert93|wgs|epsg] Default value: utm
Defines the map projection to be used.

Universal Trans-Mercator (UTM)
A system of transverse mercator projections dividing the surface of Earth between 80S and 84N latitude.
Lambert II Etendu
This is a Lambert Conformal Conic projection mainly used in France.
Lambert93
This is a Lambert 93 projection mainly used in France.
WGS 84
This is a Geographical projection
EPSG Code
This code is a generic way of identifying map projections, and allows specifying a large amount of them. See www.spatialreference.org to find which EPSG code is associated to your projection;

Universal Trans-Mercator (UTM) options ¶

Zone number -map.utm.zone int Default value: 31
The zone number ranges from 1 to 60 and allows defining the transverse mercator projection (along with the hemisphere)

Northern Hemisphere -map.utm.northhem bool Default value: false
The transverse mercator projections are defined by their zone number as well as the hemisphere. Activate this parameter if your image is in the northern hemisphere.

EPSG Code options ¶

EPSG Code -map.epsg.code int Default value: 4326
See www.spatialreference.org to find which EPSG code is associated to your projection

The input color image -incolor image Mandatory
If the color image has 4 bands it will be interpreted as Red, Green, Blue, NIR. In other cases, only the first one is used (gray scale colors). The color values are expected in the range 0 - 255, and will be embedded with each 3D point of the PLY file.

The output Ply file -out filename [dtype] Mandatory
The output Ply file will contain as many 3D points as pixels in the input DEM.

Examples¶

From the command-line:

otbcli_GeneratePlyFile -indem image_dem.tif -out out.ply -incolor image_color.tif

From Python:

import otbApplication

app = otbApplication.Registry.CreateApplication("GeneratePlyFile")

app.SetParameterString("indem", "image_dem.tif")
app.SetParameterString("out", "out.ply")
app.SetParameterString("incolor", "image_color.tif")

app.ExecuteAndWriteOutput()

Limitations¶

The input DEM image has to entirely fit into memory.