Subtitle: Going to ridiculous lengths to understand what doesn’t work with PhotoScan.
I took two sample videos with the GoPro a few days ago, of Dan and Rider. I want to print a color 3D model of them (shapeways, small), just to see it done, and to have a simple process to do it. But it keeps not quite working, and its annoying me. So, here goes another night of experimentation. What am I missing?
Here’s the precalibration stuff from Agisoft Lens, btw:
Check #1. How much does it matter how close or how far apart the frames are?
Here are sample reconstructions using just two frames – varying the number of frames apart. I’m using 4mm as the focal length, but I will play with that in the next section. Process: Align on High, Dense cloud on High. The picture on the right is what Frame # 0 looks like; the screen capture is “look through Frame 0”, zoom out to bring the head in frame, and rotate left (model’s right) about 45 degrees.
|1 frame apart (cannot build dense cloud)
2 frames (cannot build dense cloud)
4 frames (cannot build dense cloud)
||128 frames (cannot build dense cloud)|
|All 8 frames
||Above view, to see how the cameras are aligned
Clearly, more pictures is not the answer. The best one was 0 to 32, which was about a 6 degree difference.
Check #2: Trying every 32 frames, how does adding more pictures improve quality?
This time I’m moving the camera up so I can see the “jaggies” around the edges
|3 Frames combined (0,32,64):
||4 frames combined:
|6 frames combined:
||7 frames combined:
The same 7 frames, this time with the wall in view, trying to line up the roof and the wall:
Check #3: Focal Length
Trying to solve for the wall jagginess.
|6mm:||8mm: Cannot build dense cloud|
Okay, so .. 4.5 is wonky, but 4 and 5 are okay? Its very hard from this angle to see any difference in quality between 3,4,5 and 6. 2, 7, and 8 are clearly out**
Maybe another angle:
** Or maybe 7 is not quite out yet. Turns out, I can “align photos” once.. get one result.. then try aligning again .. and get a different result. So I retried 8 a couple of times over, and I got this:
None of this is making any sense to me. I guess I’ll stick with 4mm, for lack of a better idea. Do you see any patterns in this? Moving on.
Check #4: Low, Medium, High Accuracy?
I’ve bumped it up to 17 cameras (32 frames apart). Testing for “Align Photos” accuracy (Low, Medium, High) + Dense Cloud accuracy + Depth Filtering
|High, High, Moderate
||Low, Low: Cannot build dense cloud.
Medium, Medium, Moderate
|High, Medium, Moderate
||High, High, Mild: (Mild took around 3 minutes)
|High, Ultra-High, Aggressive: (12 minutes)
||Close up of H/UH/A:
Aggressive is definitely the way to go; however, there are still way too many floaters!
Ah, but this image might clear that up a bit. It has to do with the velocity with which I was moving the camera. I slowed down. Hence several of the frames are not very far apart. I might need a different approach for frame selection.
Test #5: Compass Points Approach
I will attempt to bisect angles and derive frames in that manner. Note that I’m not going to try the full 360 – I suspect that the subject moves a bit, so it can’t connect 359 back to 0; instead, I’m hoping to get a nice 90 degree profile, and maybe merge chunks to get it down to a single model. So lets try to get a set of frames from the image on the Left (000) to the image on the Right (400).
- 0,200,400 – Aligns 2/3
- 0,100,200,300,400 – Aligns 5/5, but fails to build dense cloud
I have to cut this blog post short here – it looks like I have WAY too many images, and Live Writer is freaking out. Doing a quick edit past, and then posting this as a part 1/N.