Introduction to Metashape

AgiSoft Metashape is a photogrammetry application that can be used to create 2d or 3d models from images. You can download and install a fully functional 30 day trial for Mac or Windows here: https://www.agisoft.com/downloads/installer/

Getting Started

It is important to collect high quality images of the object to be modeled from different angles. When taking pictures keep the following guidelines in mind:

  • Make sure images overlap by about 50%
  • Take images from a number of angles including looking down from above as well as looking up from below
  • Make sure to get images for every surface such as underneath overhangs or crevices
  • Harsh shadows will not render well, try to take pictures with diffuse lighting or on an overcast day of possible
  • Take more pictures than you think you will need. You can remove duplicates and only use the best images when you start the process.

To create a model in Metashape you will mainly work through the steps in the Workflow menu. The necessary steps vary a little depending on the desired outcome – 3d model, orthophoto etc:

  1. Add Photos
  2. Check Image Quality
  3. Mask Images – Recommended for 3D models
  4. Align Photos
  5. Set Bounding Box
  6. Build Dense Cloud
  7. Clean the Dense Cloud
  8. Build Mesh – for 3D models only
  9. Build Texture – for 3D models only
  10. Build DEM – for 2D orthophotos only
  11. Build Orthophoto – for 2D only

Add Your photos

To add images you can select individual images or add an entire folder. Once your images are loaded you can see them in the Photos tab at the bottom of the screen. Photos are referred to as cameras in Metashape. You can turn cameras on and off. If you want to remove a photo you can disable it or delete it from the project.

Estimate Image Quality

After importing your photos it is a good idea to Estimate the Image quality to see if any are poor quality and should be removed. To do this look in the workspace pane on the left. Expand the items until you see your images under the camera heading. Right click on an image and choose “Estimate Image Quality…” In the next dialog box make sure to choose to Apply to All Cameras. Once this process is complete you can view details (ADD SCREENSHOT) in the photo pane and look at the image quality column. If you have some images with measurements that are significantly lower than others you should remove them if possible.

Align Photos

Under the Workflow menu select “Align Photos”.

  • Higher accuracy setting will take more processing time,
  • If you have a large number of images (more than 100), we recommend you enable – Generic preselection option, to reduce processing time;
  • Agisoft does not recommend using the parameters: Guided image matching, Adaptive camera model fitting;
  • For Key point limit the recommended range of 20 000 to 100 000;
  • For Tie point limit the recommended range of 2 000 to 40 000.

Set the Bounding Box

This step is critical but often overlooked. After you align your photos you will see their locations represented in the Model window. You may want to turn off the cameras depicted as blue rectangles so you can see the tie points more clearly. You will want to resize the bounding box so that is fully contains your object with as little extraneous points as possible. This will save time in rendering and cleaning the model later. To do this use the Region tools: Resize, Rotate and Rotate region.

Build Dense Point Cloud

Select “Build Dense Cloud” from the Workflow menu.

  • Agisoft recommends you use – Medium quality. Higher quality takes quite a long time and demands more computational resources, but allows for more detailed results generation.
  • If the geometry of the scene to be reconstructed is complex with numerous small detail on the foreground, then it is recommended to set Mild depth filtering mode, for important features not to be sorted out).

Clean the Dense Cloud

To improve the quality of your model you should now look at the dense cloud and remove any extraneous points using the selection tools on the toolbar. Make sure you are viewing the dense cloud by clicking on it in the Workspace pane.

Build Mesh (for 3D models only)

Think of the mesh as the wireframe the imagery will be covering. The more detailed the mesh the finer detail in the structure but not necessarily the image. Mesh quality is more important for 3D printing than a digital model. A mesh can be based on the dense point cloud or a depth map. Using the depth map approach “supports GPU-acceleration and mostly provides better results for the same depth maps quality for objects and scenes with big number of minor details.” To generate the mesh choose “Build Mesh” from the Workflow menu. Recommended values:

  • Source data: Depth Maps
  • Surface type: Arbitrary
  • Quality: Medium (higher will give better quality but will take more processing time and generate large file sizes)
  • Face count: medium (higher quality increases processing time and file size)
  • Interpolation: Enabled

Build Texture (for 3D models)

Building the texture will add the imagery to the mesh frame. Start with the recommended settings:

  • Texture Type: Diffuse map
  • Source data: Images
  • Mapping mode: Generic
  • Blending mode: Mosaic
  • Texture size/count: 16000 X 1
  • Enable hole filling and ghosting filter

Build DEM

A DEM is a Digital Elevation Model. You should create a DEM before creating an orthophoto which is just an image that contains geographic coordinates. In the DEM settings window choose dense cloud as the source data and the defaults should be fine for the rest of the options. You could use the mesh as your data source but the dense cloud will generally give more accurate results.

Build Orthomosaic

When building the orthomosaic select the DEM as your source and leave the other options at their defaults. You could build it from a mesh as well but using the DEM should result in a higher quality model.

Exporting a final product

To export a 3d model choose export under the file menu and choose model. We recommend saving as an obj format. This is a commonly used format that can be used to view the model online or a computer and it can also be 3d printed.

To export a DEM or Orthophoto choose those options form the Export menu under the file menu. The defaults will be fine for most uses.

The post Introduction to Metashape appeared first on Trinity College Educational Technology.