Millimeter paper drawing to project on a mesh

[stasilein@mail.ru]

Does anybody know if it is possible to drape (texture) a mesh with a scanned older millimeter paper drawing (archaeological plan or strat. wall). Meshes to be created from a set of digitized height points and to sport to Metashape for further draping. The goal is to reconstruct an old archaeological trench and match those shapes in one model for fiurther manipulations? May be some other apps would do that better? Any help is greatly appreciated. Thanks in advance!

[chrisd]

The texture mapping from Metashape is a texture atlas, which breaks the mesh surfaces into multiple smaller areas with corresponding small areas of the photo imagery for efficiency.
You would not be able to simply substitute a new texture map.

To accomplish what you want you would need to define new UV mapping, and you would have to determine a mapping method that will not distort the grid in the new texture.
Its possible this could be done in Blender or a similar app, but it is a non trivial process.

Hopefully others here can further clarify this as texture mapping is not my expertise.
At a mimimum, I think you would need to allocate a significant amount of time into defining a workflow and learning to use the tools that will accomplish what you want. And then there's the time you would spend actually doing the work.

[macsurveyr]

Quite a few years ago, I documented several petroglyphs that had Mylar tracings done in years prior to photogrammetry captures. I laid out the Mylar tracings and photographed them from multiple perspectives and convergent angles so I could align the images and make a photogrammetric project of the tracing. I could then pick points on the actual petroglyph project at real world scale and pick the same feature in the tracing and call them “control points” to reference the drawing in real world coordinates. You need at least 4 points. A single scan of the drawing doesn’t work as well and also, perhaps the detail, or lack thereof on the drawing may make it difficult to find common points but that is up to you to determine. Perhaps this technique will work for you.

Tom

[stasilein@mail.ru]

Many thanks for your replies! I think the workflow is quite simple here:

1. Create four plain vertical meshes for trench walls each by 4 XYZ points in local coordinates (these meshes are rather plain rectangulars in this case);
2. Align scanned drawings to each wall mesh;
3. Create meshes for trench planums by digitized paper height points;
4. Project scanned drawings of the planums onto the corresponding meshes;
5. Combine created textured models (stl, obj, dae etc.) of the four aligned walls with a number of planums in a single model, textured with scanned drawings for further manual stratigraphy digitalization and modeling of solids from it.

Numbers 1-3 are more/less realizable in AutoCAD. Number 4 may be QGIS can do.  But number 5 is a real trouble by means of procedure simplicity and final results. By now I have no any progress in this step. I even thought of doing tsome of the steps or the whole process on iPad Pro 11 with Apple Pencil, but have found neither easy way nor app.

Of course it would be great to organize the whole process inside the Metashape.

I'll go on anyway and in case of success will post here, but your advises are much appreciated.