The Key to Cleaner 3D Scans: Cross-Polarization

Today’s tutorial teaches you everything you need to know about Cross-Polarization. The necessary hardware/gear, and why it matters. It is absolutely essential if you’re trying to scan an object that has a very shiny/reflective surface. Taking a look at the renders in Unreal Engine 5, it doesn’t take long to see the vast difference between the two approaches, the cross-polarized result is FAR superior. The scans done in this tutorial were made with RealityCapture.

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Important links:

MAJOR THANKS to Grzegorz Baran for his in-depth guides and insights on photogrammetry. Find his channel and video I referred to here:

Necessary gear for Photogrammetry:

Flashes:

Polarizing Filters:

Transmitters and Other:

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Timestamps:

00:00 - Intro
01:00 - CapturingReality
01:30 - What is Cross-Polarization?
03:39 - Polarization Explanation
04:46 - Necessary Gear/Hardware
05:56 - Gear: Polarizers
07:49 - Gear: ColorChart
08:07 - Gear: Transmitters
08:53 - Assembling the Camera Rig
09:12 - Why do we need this?
10:21 - Important Steps Before Shooting
11:47 - Scanning
12:28 - Into RealityCapture
13:36 - Limitations of Cross-Polarization
14:53 - Conclusion & Thanks

---------Cameras and Gear Used To Film This Video -------
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My Streaming / Recording Setup (How this Video was Recorded)

[DominikMorse]

Wake up. Browse notifications.
William's video.

This is a good day!

[gavinmetzler]

I can't find it anymore, but someone once had a blog about a capture setup that was very cool. If you use a point source light (small flash bulb) and reflect it off a parabolic mirror, you can get collimated light. I forget all the technical details, but if you have cross polarized collimated light and you know the relative angles between your light and camera, you can then work out the angle of reflection and get a reflection map. It may have used Brewster's angle, I can't remember. I think you can separate metal from dielectric using Brewster's angle.

[tasoschristodoulides]

A second issue regarding the Polarization phenomenon is about the Angle we are shooting at a surface. Avoiding extreme angles (like 0 degrees: almost parallel or 90 degrees: looking down at the surface) shall give better results in cross polarizing. There is an exact angle which cancels out almost 100% of reflected light; the angle depends on the material of the reflective surface, i.e. the refractive index of that material. Varnish, oil, water have different indices, so the angle varies.

[diomiziofattorelli]

Amazing William! I have heard about cross-polarization for textures and 3d models generation for years but I had no idea that there was a pratical and affortable way of doing it. Thank you for your amazing work!

[TheLegendOfTerry]

I'm glad someone is finally sharing this. This is common practice for ingesting assets at most film studios.

[jimmysgameclips]

I really appreciate your step by step approach, this all feels so crystal clear

[kocurel]

your insight in subject is so detailed I'm amazed

[jonva]

So timely! I've been working on a cross polarization setup recently.

[TheLordDino]

Really nice info William, thanks. Can't wait for the glass approach. I work with plastic bottles, and a couple months ago did try to see if I could use photogrammetry, but PET/HDPE/PP bottles have a lot of problems to overcome. glare, reflection, transparency, repetitive features(or none at all) you name it :D

[jobimd]

Very neat results! I had quite similiar results with a 50 € Tiffen circular polarizer 52mm filter, a 80€ godox flash, a 25 € diffuser and a 20€ sheet of polarized film.

[aresaurelian]

I approve. Now if we could use these techniques to get a 'clearer picture' of the micro cosmos....
Excellent production. Thank you.

[wilismatrix]

Thanks William, I do photogrammetry and I was looking for a big budget flash, I was interested in the godox but didn't find anywhere a showcase of how much strong it is until you have done it. Thank you very much, now I know that it is the better choice 😀 also for small object you can use a rotation table like the foldio 360 which will automatically rotate and shoot at a predefined angle, in my case I use 10° so 36pics for each circle. it speed up the workflow and makes it so much easier.

[sambrown]

Omg! I can’t wait for glass photogrammetry! Every one of your vids is so valuable and stacked with information- thanks for all your instruction!

[DIRECTEDbyRAY]

Great to see you're so close to 100k subs! Congrats William!

[zinetx]

Great video! Informative & fun to watch.
I'm really thankful I found your channel last year.

[MitchellFX]

You always make videos when I am working on this exact task. Great timing and great info as always!

[reffect]

Great tutorial ... again! It looks like, you will hit the 100k follower barrier soon. Congrats to this in advance. You deserved it. Off-topic question: What benefits registered people will get, when they pay for a membership of your channel? Thank you so much William and please go on!

[tasoschristodoulides]

This is such a great presentation of the cross-polarization method for eliminating reflections.
I just wanted to mention that Polarization as an optical phenomenon can be exploited only on Non-Metallic surfaces.

This means that polarized light can not be fully or partially cancelled when we are dealing with metallic objects. Which are photogrammetry's worst "enemies".
That is why we use fine powder sprayed on metallic surfaces to eliminate all metallic reflections. We lose the albedo - which is kind of black-ish anyway on most of metallic surfaces.
I'm not sure if there is any other method out there for metallic or semi-metallic objects for photogrammetry/3D scanning.
Any ideas are welcome.

Again, thanks for your fantastic tutorials, William!

[WilliamAllard]

Great video. It's given me a lot to think about regarding my set-up and why I was having so much difficulty with my last scan project.

[jimmwagner]

Definitely saving this for later reference. Great content as always!