Geometry Closing

Every solution supports closing holes in the generated mesh, a useful feature that would take a long time to do manually otherwise. If this feature is optional in Zephyr and PS, it seems RC is doing it automatically and I didn’t find any way to disable it, which is sometimes undesirable for single-sided meshes or meshes with strongly concave areas.

Workflow

All three solutions make the user progress along a workflow. Zephyr is especially detailed in this area, densification is handled separately and can be operated both during mesh generation and mesh export providing fine control over the final rendering.

Point Cloud Edition

It is sometimes useful to remove points from the dense point cloud before reconstructing the mesh. This helps in preventing unwanted geometry which would otherwise be more difficult to remove once the mesh is built. Both Zephyr and PS provide this functionality. However, since RC goes directly from sparse point cloud to mesh, there is no way to do this. Also, even though RC provides point selection tools, it doesn’t seem possible to remove points from the sparse point cloud.

Time Management

All solutions provide duration estimates for the time-consuming processes. They are however not always reliable, as they adjust as processing is progressing. They also all provide a cancel button for long duration operations, but not always responding promptly (like on mesh export). All solutions have a pause/resume functionality which is convenient to temporarily free up resources during a long processing.

Photo Quality Rating

Both Zephyr and PhotoScan have a photo quality rating functionality which helps to triage photos especially when the set is large, and individual review of each photo would be tedious.

2.5D Mesh Reconstruction

As seen for the “Rock 2” series, the 2.5D reconstruction feature of PhotoScan can be used for surfaces and confers a significant speed boost to the reconstruction process making it a great solution for this type of object.

Merging Point Clouds

Even though not used during these tests, the ability to merge separate point clouds to form a single mesh is useful when an object cannot be reconstructed in a single pass (i.e top and undersides of an object). PhotoScan Standard provides this functionality. Zephyr has a project merging feature which can be equivalent but not in the Lite version tested here.

Configurability

In terms of parameter tweaking, as was seen in the above testings Zephyr has a good range of options which can affect the output result. RC has a few but apparently not as much, and tests with dnf/ltnf modifications were not convincing. PS has very few visible options there, however, tweak parameters can be added in Preferences, but since they are not visible, they are hardly usable. Having lots of options is not necessarily useful to everyone, and it may be made to the detriment of simplicity; however not in the Zephyr case as the user is free to choose the level of details to go into.

Conclusion

As was stated in the opening of this article, very few objects were tested here and only a subset of the features of each solution was used. The evaluation was based on perception only, not numerical data. Also, software solutions constantly evolve, like Zephyr in its upcoming “Blueberry” version is said to improve both depth map generation quality and speed, among other things.

All reviewed solutions were able to deliver good results, in particular knowing the 8K resolution is a bit extreme. Downscaling maps to 4K or 2K provides sharpening opportunities that would tend to make maps look more alike.

All things considered, test analysis showed recurrent behaviors which can help better understand how each solution is processing data. After having performed this review, I find the solutions to be complementary, each of them having some strong or improvable areas, and sometimes unique features. I think If an “ideal” solution was to exist within the context of my workflow, it would probably have the speed of RC, a mix of geometry generation from RC and Zephyr, the configurability and versatility of Zephyr, a mix of texturing abilities of Zephyr and PS and features of PS such as 2.5D reconstruction and dense cloud merging.

Olivier Lau, developer / technical artist at Eyosido Software