Tracing of prehistoric rock art

[mwillis]

Hello everyone, I'm looking for some advice.  I've been creating high resolution 3D models of complex prehistoric rock art found in European caves using PhotoScan.  Now that I've generated my models, I would like to then "trace" the artwork on the 3D model to make it stand out.  Ultimately, I would like to show the shape of the model with only my tracing on top.

The 3D shapes I am working with are extremely complex and it isn't as simple as exporting a flat ortho photo to trace in Photoshop.

Has anyone done anything similar?  Any suggestions are most welcome.

Thanks,

Mark

[MitchellT]

Hi,
I have been doing this with ZBrush. If you have access to ZBrush, I can outline the process as it currently stands.
Mitchell

[mwillis]

Mitchell, thanks for the reply.  I played around with Zbrush many years ago but haven't used it recently.  Would you please share you're work flow and I'll purchase the software?  Let me know if you'd prefer to do this over email.

Thank you,

Mark

[MitchellT]

Mark,
Drop me your info at mitchella1a@gmail.com
Mitchell

[davidpmcg]

Hello Lads,

I came across this post under a, 'rock art', search. I hope you don't mind me butting in?

I (well, the colleague I am helping who is not a native Eng speaker) am similarly hoping to trace paintings from a large rock panel in a cave using, 'corel draw'. We have already built a pretty crisp textured model and are now wondering what the next step should be?

As in your case, Mark, the surface is complex and the end product would show the shape of the model with only the tracing on top.

Apologies for this unrefined description, but, I was wondering if exporting an .obj into a mesh ed app then 'unrolling' the concave surface of the rock wall to become a flat, 2D image to trace would be ideal? Or would that distort the paintings?

Thank you in advance,

David

P.s.
I watched your youtube animation from Guam, Mark, very impressive!! How did you create that?

[JMR]

You can make use of virtual polynomial texture mapping as a helper, it will allow you to make engravings more readable by moving a virtual light source while you (asuming that you have some experience in rock art) try to undersand what you are seing.

You also might want to try an innovative technique that has been developed by a friend of mine called Hugo Pires. you can find some literature about his procedure that ha has called MRM (morphological residual model). I can help you to contact him if you want.

https://www.researchgate.net/publication/306202065_Morphological_residual_model_A_tool_for_enhancing_epigraphic_readings_of_highly_erosioned_surfaces

https://www.eagle-network.eu/wp-content/uploads/2014/01/Eagle_ppt_MRM_Pires-et-al.pdf

https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XL-5-W4/415/2015/isprsarchives-XL-5-W4-415-2015.pdf

regards

[davidpmcg]

Thank you for getting back to me so quickly, JMR.

MRM looks like a great tool that could come in handy on site. I am tracing paintings (hand stencils etc), not etchings, so MRM is probably not the right tool for me on this project.

Thank you again.

[SAV]

Hi mwillis,

Alternatively, you could trace features on your dense point cloud using CloudCompare (free, open-source). Export it as LAS or LAZ file from PhotoScan and then open in CloudCompare.

Trace polyline:
http://www.cloudcompare.org/doc/wiki/index.php?title=Trace_polyline

or

Semiautomatic trace tool of the Compass plugin:
http://www.cloudcompare.org/doc/wiki/index.php?title=Compass_(plugin)

Regards,
SAV