interior image acquisition tips?

PIX4Dcapture PIX4Dcapture Questions/Troubleshooting
1

Hello, I am still a Discovery user. Can’t quite make it work yet. Otherwise I would’ve been on a pro license.
So I come here for an advice.
I was shooting an empty interior office concrete shell (with some trash around). Hoping to get an interior model.
Beforehand, I did read articles on it and watched the seminal but still failed miserably to produce a usable model. So I’m hoping to pick up some interior image acquisition tips here.

So here is what I did: I walked around the rooms with GoPro Hero 3. Every 1 meter or so I shoot an image pointing at nearby walls (1.5 to 2 meter away). One round pointing 45 degree up to get ceiling and one round pointing down to get floor.
The result: half of the images did not calibrate and the model was incomplete.
I noticed that the images that were shot against bright windows left the interior way too dark. So these images did not register. Then walking through a door almost certainly was losing the chain of connected images. Another one, was shooting a narrow corridor. the end of it gotten really distorted because I was walking along the corridor and shooting straight. So there were little triangulation distance for the end of the corridor. Then I walk to the end of the corridor and turn around the connection was lost too.
So, Here are the ideas I will try for the next attempt:

  1. Shoot with a strong projector. I’ll get a strong handheld projector and will mount my gopro on it. So even if there is light coming from the window - the projector will overpower it - giving me rich detail. This will also help to increase shutter speed for crisper images.
  2. Shoot at dusk or at night so outside lighting interferes even less.
  3. When going through a doorway - shoot at the floor as it is continuous. That may provide a connection from room to room. Shoot double the rate at the doorways.
  4. never rotate the go pro more then 30 degrees at a time. When changing direction , especially in narrow corridors, small transition angles will provide continuity. (I know not to keep the camera in the same location while rotating)
  5. Never point straight in the direction of walking. Shoot sideways. Especially in narrow corridors. Pointing straight )) is pointless.

Please, continue the list. Hopefully it will lead to some useful interior models

2

comment to #1. I will add a sheet of white paper over searchlight to disperse the illumination.

3

Hi Dennis,
Thanks for sharing on the forum!
Interior mapping is possible with Pix4Dmapper but indeed it can be difficult.

In general, it is needed to have a very high overlap, around 90%. That is why we recommend to use a fisheye camera such as the GoPro. As you experienced, it is nevertheless easy to loose the connection in the image chain and this makes the reconstruction difficult.
Adding manual tie points will help a lot adjusting the model. To add manual tie points in the rayCloud:
https://support.pix4d.com/hc/en-us/articles/202560349

We would also recommend to use a tripod to stabilize the images. Especially if you shoot at dusk or when the lighting conditions are low. To avoid having too much reflection from outside, you can also consider shooting during a cloudy day.

Using an artificial light such as a strong projector might make the shiny surfaces even more shinny. Depending on the environment that you want to map we would not recommend to use an artificial light.

Keep in mind also that shiny surfaces, glass (windows) or homogeneous surfaces are very difficult to reconstruct in Pix4Dmapper. If you have a very homogeneous white wall, you can consider to add a poster or something to cover the wall and to give more texture to the wall.

To get more tips and advice to shoot indoor don’t hesitate to watch Olivier’s webinar:
Indoor mapping

Feel free also to try our new tool Pix4Dtagger which allows the automatic detection of targets in images, this can be very useful for indoor reconstruction.
https://support.pix4d.com/hc/en-us/articles/hc/communities/public/questions/203465445

Regards,