Texturing models with inconsistent lighting

I’m thinking about this issue for some time and I haven’t found a satisfying solution yet. Now I’m working on a scan of a small church that is why I will use it as an example. Differences in brightness inside are huge. The difference between lightened by the windows wall and the darkest corner it can be even 10 ev. The color temperature varies. I use three different cameras so each sensor reacts differently on tint etc. Possible solutions:

  1. AUTO MODE (shutter speed) - I’m scared of this. In theory, the camera will choose proper exposure and I will pass smoothly between the darkest and lights part of the church. I expect that texture generated this way can give hard passes that need to be avoided. Even if generate texture from point colors, it can give some unwanted results.

  2. HDR - It will produce nice input but… the quantity of the photos can be just too big. The first day I took 1,5k photos. Due to having smooth passes between stacked exposure I usually use more than 3 stacs. Depending on EV scale of the interior I’ll need from 5 to 11 photos for the stacks. 1,5k x 11 and tomorrow the same? 30k photos to process and I’m gonna use information from max 30% of those. Not so efficient.

  3. ONE exposure - Using top DSLR it is possible to achieve 14ev of dynamic range. In theory, picking a middle value and aligning exposure in postprocessing should give usable photos. The problem will be low quality of the details in the shadows. This solution is also far away from being perfect because the size and weight of FF DSLR can be a huge obstacle to use it for an example from a drone.

Even if exposure problems will be solved there is still color temperature inconsistency and tints. I’m sure that there are some solutions in postprocessing that allows for obtaining decent results. Texturing from the only one serie of photos that are made fast to catch lighting conditions? If it is possible… Texturing from chosen photos? This workflow seems to be painful… or maybe there is some software solution I don’t know. What idea do you have? What are you doing in this kind of objects?

My instinct would be Full Auto - but then I am lazy :slight_smile:. As you say, once you’ve reconstructed the model you could select only certain images for the texturing.

What is the use case for the output 3D model?

Is it essential to capture the space during the day? Could you capture at night with a ring flash and controlled lighting?

Maybe @artfletch would have some advice.

Haven’t tried it yet, 'cause it’s brand new - have you considered using the free Agisoft De-Lighter (https://www.agisoft.com/index.php?id=71) on the already reconstructed model to get rid of shadows and highlights?

As for the tint etc.: Do you use a RAW workflow? I mostly prefer out-of-camera JPGs for photogrammetry, but if you have problems with white balance and colours, this might be a possible way…

“As you say, once you’ve reconstructed the model you could select only certain images for the texturing.”

Yea, I was thinking also about use 360 HDR photos to texture model. In this case, I don’t have to take care of exposure when capturing details. There is even one company that is producing 360 cameras dedicated to that. I need to check if there is any advantage of using this product by comparing with “normal” 360 rig. The only problem is that I’m not sure that I will have enough information and it will be quite easy to produce some hole in the texture.

“What is the use case for the output 3D model?”

The goal of this reconstruction is… to be amazing :). It is just workflow preparation and cost optimization for future work that will start in 3 months. Here I have a comfortable situation and time that is why I can check the most efficient solutions.
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“Could you capture at night with a ring flash and controlled lighting?”

If I use 360 camera for texture reconstruction I cannot use ring flash. Using ring flash for a few thousands of photos can be a bit complicated. I was thinking about placing many flashlights inside but if I follow this idea, the project will turn to a bit more expensive, complicated and time-consuming. For sure this is a solution but not the first choice.

"Haven’t tried it yet, 'cause it’s brand new "

I have it already installed on my PC. This is a tool that allows to eliminate shadows. Not exactly the same issue.

“Do you use a RAW workflow? I mostly prefer out-of-camera JPGs for photogrammetry, but if you have problems with white balance and colors, this might be a possible way…”

I never shot JPGs. And I advise you also to avoid this. You lose a lot of information. The images are also processed so you have extra artifacts. It is better to shoot RAW and then convert it to JPG rather than use JPG directly. The problem is not, that my camera settings are changing. The light temperature changes. And also, colorful glass produces tints. So to calibrate light source properly I need to change the white balance. So you can imagine texture that is blended from two images with WB set to 5500 and 3200. I will take a screenshot that shows what the problem is about.

I was hoping for some super smart software that aligns photos histograms or can blend textures easily. I found also software to colorize point clouds. I’ll check it and share info.