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.