Photogrammetry software needs to make assumptions when it has nothing more than color information.
Specular highlights are going to be clipped/clamped to white or something similar. Therefore, if the software sees white, how is it to know whether it is a specular highlight vs. just something colored white? That is the problem. In the case of transparency, how does it know the difference between a textile pattern vs. colors poking through multiple surfaces? Providing multiple angles of the same subject can help resolve those issues because the software can cross reference the details as perspective changes and see the parallax shift, but if the subject is highly reflective or glossy the specular highlight will travel around the surface as you change angles. Therefore, you may need to feed additional images to the software to give it more information to resolve the problems, and those problems may not be fully resolvable unless you make adjustments to lighting - or do what a lot of the 3D scanner companies do in their demos - apply dust/powder to the subject to remove glossiness and transparency. At that point It's not much different than making multiple passes with a 3D scanner and using registration points to align the geometry after the fact. These issues are less problematic with 3D scanners because the sensor has more information at its disposal from scanning the subject directly and can differentiate using alternate information such as intensity of light, by using different wavelengths such as infrared, or different technologies altogether such as sound waves. Actual technique varies with the scanner. Matt From: [email protected] [mailto:[email protected]] On Behalf Of Manuel Huertas Marchena Sent: Wednesday, June 04, 2014 11:20 AM To: softimage list Subject: RE: Photogrammetry - what do you use? Hi Stephen, I am curious to why it does not work with transparent/shiny objects (havent really done any test with those kind of surfaces..). Do you mean that the calibration for the point cloud isn't accurate? what software & workflow are you using? ________________________________ Date: Wed, 4 Jun 2014 14:13:28 -0400 Subject: Re: Photogrammetry - what do you use? From: [email protected]<mailto:[email protected]> To: [email protected]<mailto:[email protected]> Be aware that there is no Photogrammetry solution, that I have found that will deal well with transparent and/or shiny objects. I do a lot of product modeling, from prototypes, and I have not found any Photogrammetry solution that works better than taking front, side, top, and 3/4 view photos, and using the rotoscope function in my views. I have tried many. I am hoping that the new 3D scanning for ipad will be better, but it looks similar to other methods. https://www.kickstarter.com/projects/occipital/structure-sensor-capture-the-world-in-3d I wish someone would come out with a 3D scanner that is based on sonar principles. Image based 3D scanning has so many issues. The laser scanners are nice, but have issues with undercuts as well as transparent and shiny surfaces. If you do find a solution, that works well, please post back here. On Wed, Jan 29, 2014 at 10:08 AM, Marc-Andre Carbonneau <[email protected]<mailto:[email protected]>> wrote: Hello friends, I am currently investigating photogrammetry and would love to get your advices, opinions, experiences with such systems. What hardware do you use? Which software? Best practices? Thank you for any info! MAC [cid:[email protected]]<https://mdc-web-tomcat17.ubisoft.org/confluence/display/technologygroup/Home+Passenger> Marc-André Carbonneau Product Specialist -- Best Regards, Stephen P. Davidson (954) 552-7956 [email protected]<mailto:[email protected]> Any sufficiently advanced technology is indistinguishable from magic - Arthur C. Clarke [http://www.3danimationmagic.com/3Danimation_magic_logo_sign.jpg]<http://www.3danimationmagic.com>
