I recently put together a portable polarised texture rig in the hope of improving my texturing workflow for handheld photogrammetry (image above). The aim for this experiment was to see whether it would be possible to use this setup to capture clean textures, suitable for relighting and rendering in Maya. Admittedly when planning the design of this setup I wasn’t completely confident that it would work due to the flashes being so close to the camera. From working on texture shoots in the past, I have learned that the polarised light source works best when positioned at a either a direct angle, or at 45 degrees from the subject. So for my portable rig to be successful I would have to shoot pretty close to the subject if I were to achieve anything close to a 45 degrees. Due to being so close, it made it important to be extra careful with exposure settings to avoid blowing out brighter, more reflective areas within the images.
Once I had refined the setup and found a way to work with all the physical limitations, it started to produce some pretty exciting results. See below images of subjects in both polarised and non-polarised states.
The higher the specularity on a surface, the better the contrast will be between the two lighting conditions. The facial skin has a lot of contrast between the two, as the oily skin produced high levels of specular reflectance in the non-polarised image. For me, the most impressive example is the carved wooden chair; you really get to see how deep the colours are in the wooden grain once all the specular is removed.
Once I found that this rig actually worked, I got a bit over excited and began clearing all the shelves in our house, collecting various objects to take outside and test on.
After scanning a whole range of different things, from pieces of fruit to a set of Russian Dolls, the object I chose to work on was a mosaic vase, made up of all kinds of reflective materials; mirrors, crystals, etc. It was an object that would usually be a nightmare to capture, but in this situation a great test for my portable texture rig.
Luckily I was able to capture a set of images that easily aligned in Agisoft and the texture map was much better than I would have normally expected when scanning a prop of this kind. The areas with mirrored surfaces didn’t come out so well, but seeing as it was such a simple object to model, a bit of mesh fixing didn’t worry me too much. For texture painting I had a go at using Substance Painter, which was a new experience for me, as I am used to only painting with Mari. I have been told that Painter is really easy to use and has some amazing tools, so hopefully after a few more mini projects I will be able to share some insight into all of this…
See below a simple breakdown of each stage on the mosaic vase.
The main focus for this project was to try and create a handheld rig that could capture polarised textures, to support a PBR workflow for relighting and rendering in Maya. Despite the minor limitations of the rig, I feel like it was definitely a success and has had a really good impact on my texturing workflow. When it comes to close range photogrammetry, I imagine I will be using this setup quite a lot in future.
See below a rendered turntable of the final textured model.
14 thoughts on “Portable Polarised Texture Capture | Photogrammetry”
Thanks, that was really interesting, can you say what rig you use for flashes ?
Are you made two iterations in agisoft with normal images and polarised for texture generation ?
Thanks Sergey! Yeah sure, I used a couple of these speedlites – https://www.amazon.co.uk/gp/product/B00PIIRO1C/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1/?tag=adamspring-21 and a wireless flash controller – https://www.amazon.co.uk/gp/product/B00M1BVYYM/ref=oh_aui_detailpage_o06_s01?ie=UTF8&psc=1/?tag=adamspring-21 – so far, both very good value for money. On each flash I taped a bit of polarising gel over the front. Also, I later bought a Godox battery pack for the flashes, as normal batteries weren’t lasting long enough. When processing the images I created one mesh using both polarised and spec images, then I would turn off the spec for texturing.
Great source of information and great results Adam! I have just one quick question, what type and size of speedlite extension bracket are you using?
Hi Niall, thanks for reading : ) the mount is made up of two 8″ dual mount brackets. You can clamp them together, but I found duck tape seemed to do the trick. Here’s a link – https://www.amazon.co.uk/gp/product/B00PAG93ES/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
Hello,
thanks for the tipp with the polarizing light flashes.
I think we should incoperate that into our photogrammetry/3d-ct setup.
Love to know your thaughts on that.
https://youtu.be/Y3y4yZD848Q
Kind regards
Swann
Very cool combining CT scans with photos! Really nice results your getting too. I can see no reason why you couldn’t polarise your lens and light sources with this setup. It’s been a while since you left this comment, so maybe you are already doing it now…
Hi Adam!
I really love your blog posts!
I’m totally new on photogrammetry and I’m looking for learn as much as possible. One thing is not clear for me is about the environment light….It was not better to shot in a dark room? The flash with the polarized film on are so powerful that the environment light are not so much relevant? I see that you shot also indoor with the use of outdoor(window) environment light.
Hi Riccardo, Thanks for your comment!
In my experience, it is best to shoot in a dark room and also have a black enclosure surrounding the subject for better polarisation.
For the vase in this post I was just playing around outside so I wasn’t too worried about the environment lighting – the polarisation seemed to work pretty well regardless. Since this post I did a few controlled tests using a studio setup and it seems that the polarised speedlites are powerful enough that the extra environment lighting has little affect on the final image.
Thank you very much for your answer. I’m now building my light set-up and I’m getting curios about your.
I’m trying to optimize the investement in photogrammetry and your speedlight setup looks very good for interior and also exterior shots. I have buy a cheap ring light but I think your speedlight have more power and are suitable also for big objects/scans…correct me if I’m wrong. Have you also scan big objects with your “speed lights setup” like a statue? Never try ring lights?
I have recently been scanning full body clothing with my speedlite setup, which has worked quite nicely. Will be sharing some results on my blog in the next week or so if you’re interested. I think a ring flash should work just as good, possibly even better. I would love to experiment with a ring flash, but the setup I have seems to be working for now so I haven’t found the need to purchase yet. If you decided to get one, I would be really interested to see what the results are like!
Hi Adam
I’ve just found you’re blogposts. There is some really useful information here.
I have a few questions. I was wondering about the light falloff from the flashes? How much leaway did you have to change the distance from your subject and keep approximately the same exposure? Hypothetically if you could find a practical way to mount the flashes further from the camera (to get the approximately 45 degrees angle) do you think if you were shooting a bigger object (a tree trunk, a shed etc.) the falloff in light intesity from the flashes would make resolving a scan difficult? Also I’m guessing if you were shooting a bigger object from further away the environment being dark would be more important?
Thank you for sharing your experiments with us!
Alex
Hi Alex, thanks for your comment and checking out my blog!
Yes you’re right about the distance restrictions. I have found when getting too close to the subject, the lights become too intense and uneven across the subject. The best approach I can think of is to stay a similar distance at all times, but swap lenses when taking wide/detail shots.
The largest subjects I have captured with this setup are mannequins with full body clothing. For this I capture wider shots with normal lighting, and then closer shots for texturing with the handheld polarised rig. Both image sets seem to align just fine in most processing softwares.
Hi Adam
How do you find this works for landscape scanning, such as rocks, floors, brick and like that. Do you find that the light rig is beneficial in terms of increasing quality, or does it not significantly affect the object after a certain distance? Say, 15ft.
Hey Adam, I haven’t tried combining this setup with any environment scanning. It would be fun to see how well it works.
It could be good to capture a polarised set of images for some of the important smaller subjects in your environment. Subjects like rocks, tree trunks, etc should work nicely. Shooting anything further than 8ft away, I think would begin to introduce uneven lighting.
Personally I only capture small subjects (head scans, shoes, props, etc) but maybe I will try and capture something bigger at some point. Will be sure to share on my website if I do…
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