Homeland Security & Civil Engineering

Agisoft PhotoScan

Overview
Agisoft PhotoScan is an advanced image-based 3D modeling solution aimed at creating professional quality 3D content from still images. Based on the latest multi-view 3D reconstruction technology, it operates with arbitrary images and is efficient in both controlled and uncontrolled conditions. Photos can be taken from any position, providing that the object to be reconstructed is visible on at least two photos. Both image alignment and 3D model reconstruction are fully automated

How it works
Generally the final goal of photographs processing with PhotoScan is to build a textured 3D model. The procedure of photographs processing and 3D model construction comprises four main stages.
1. The first stage is camera alignment. At this stage PhotoScan searches for common points on photographs and matches them, as well as it finds the position of the camera for each picture and refines camera calibration parameters. As a result a sparse point cloud and a set of camera positions are formed.
The sparse point cloud represents the results of photo alignment and will not be directly used in the further 3D model construction procedure (except for the sparse point cloud based reconstruction method). However it can be exported for further usage in external programs. For instance, the sparse point cloud model can be used in a 3D editor as a reference.
On the contrary, the set of camera positions is required for further 3D model reconstruction by PhotoScan.
2. The next stage is building dense point cloud. Based on the estimated camera positions and pictures themselves a dense point cloud is built by PhotoScan. Dense point cloud may be edited and classified prior to export or proceeding to 3D mesh model generation.
3. The third stage is building mesh. PhotoScan reconstructs a 3D polygonal mesh representing the object surface based on the dense or sparse point cloud according to the user's choice. Generally there are two algorithmic methods available in PhotoScan that can be applied to 3D mesh generation: Height Field - for planar type surfaces, Arbitrary - for any kind of object.
The mesh having been built, it may be necessary to edit it. Some corrections, such as mesh decimation, removal of detached components, closing of holes in the mesh, smoothing, etc. can be performed by PhotoScan. For more complex editing you have to engage external 3D editor tools. PhotoScan allows to export mesh, edit it by another software and import it back.
4. After geometry (i.e. mesh) is reconstructed, it can be textured and/or used for orthomosaic generation. Several texturing modes are available in PhotoScan, they are described in the corresponding section of this manual, as well as orthomosaic and DEM generation procedures.

for more information, visit Agisoft website.
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