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creates 3-dimensional objects from pairs or many images


PTStereo creates 3D-worlds from sets of photographs. Applications range from object movies to terrain visualization. Any set of images can be used without alignment requirements. 3D-data can be extracted for any feature visible in both images, as long as the images have different viewpoint (non-zero stereo base).

User input involves the triangulation of all images: Corresponding feature points have to be identified, and connected to a mesh consisting of triangles. The output of PTStereo is a 3D-world ready to be viewed with any VRML or 3DMF-browser. This world consists of a texture mapped indexed face set. In addition, world coordinates of all feature points and camera positions are calculated and can be used for measurements.

Using PTStereo:

PTStereo should be used as helper for the frontend 'PTPicker'. Using PTPicker, a text file is generated consisting of feature point coordinates and triangles.

o Arbitrary many input images can be used

o Map-to-map option: A map or ground plan of an object can be used as one of the input images.

o World coordinates of camera positions are individually settable or can be calculated.

o 3DMF output option added.

o Textures for texture mapping can be selected from different images.

o Use the front end 'PTPicker' for simple triangulation.

More Uses:

(1) The final Project file contains vertex coordinates in Meshwork syntax. These can be cut and pasted into mesh file to generate a 3D-mesh for editing in Meshwork.

(2) The final Project file contains commands ('o'-lines) for Panorama Tools: Execute these lines in the adjust-submenu (mode 'insert', 'use script') and the images texture0.jpg and texture1.jpg are transformed to have parallel film planes. They can then be used for view interpolation with any Morphing software, or for stereo viewing.

Accuracy depends on the distance of an object relative to the stereo base. Distances much larger (eg > 20 times) or features much smaller than the stereo base are not well resolved.

Basic Steps:

Download example project Start 'PTPicker', and open the file 'Project_vrml' from the File menu. Alternatively, you can drop it onto PTPickers icon. In the menu 'Images' you will find a list of 3 images belonging to this project. You can open images from the list for viewing and setting control points, or triangles. For now, leave the images and points unchanged, since these have already been set.

Open the 'Project' menu and select '3D Stereo' in the 'Project' menu. You will be asked for a name of the result, and you can accept the suggestion 'Result.WRL'. This file must be saved in the same directory as the image files. To interactively view the scene, you need a VRML browser (for a list of mac-viewers check, for me Cosmoplayer works best). Open Result WRL in the viewer and navigate according to the viewer docs.

Alternatively, a 3DMF output file is created by using the supplied project file 'Project_3dmf'. This file is very huge, since it contains the images in an uneconomic ascii format. Use this format only for exchange with other graphic editors. Using the supplied large images may cause problems viewing the file with the Quickdraw viewer. On my system this only works if the images are scaled down by a factor of 4.

Script Formats:

PTStereo supports any number of images for one scene. The sample script "3D Object" in the 'Project Models' folder is one to be used for two images. You can change lens type (eg to fisheye) according to the syntax outlined in the "Optimizer script". The line starting with 'p' (Panorama description) is a dummy line and should be left as it is.

Starting a New Project:

Put the images belonging to the object into one folder, start 'PTPicker' and click 'New' in the File menu. Choose one of the available Project Models, and save it into the folder with images. Then open images from the 'Image' menu. The first time you click on an image, you have to find it, but then its name is remembered. Set a couple of control points for each pair of overlapping images, and periodically save your work. Then set triangles which indicate which image should be used for texture mapping. Finally, call 'PTStereo' from the menu.

current version of PTStereo is 2001/12/02 provided by Helmut Dersch with his last distribution of PanoTools bundle.