Check out our YouTube Tutorial on High-Resolution Interior Photogrammetry with Polycam!
Understanding the Three-Pass Capture Workflow
Here's my process for capturing extremely high-resolution scans of a interior space. The first thing I do is that the-- I basically do three passes of the space. There's with my back to the wall, there's the center ring, and then there's details.
Capturing the Outer Ring Pass
So back to the wall. The process here is you start in one place. I like to start at the door 'cause it's easy to remember when you've made your way around the entire space. And what I'm gonna be doing is taking a bunch of photos, taking a single footstep to the left, taking a bunch of photos, taking a single footstep to the left, um, and basically going around the whole space.
Capturing Corners and Angled Walls
When you get to a corner, you're gonna be taking all those photos forward and then all those photos at a forty-five degree angle, and then all those photos at the ninety degree angle, and then continuing. Um, this is a forty-five degree wall, so it's a little easier.
Maintaining Photo Overlap
Uh, but you need all of your photos to have at least kind of thirty percent, ideally closer to fifty percent overlap between them. And then your process for taking the photos should be not just holding your camera at eye level and rotating it. You want some parallax, you want some difference in the viewing angle. So I like to aim the camera slightly down at the ground. Photo, photo, photo, photo, photo, photo.
Adjusting Photo Density Based on the Room
I kind of take somewhere between five and six photos, depending on a lot of things, depending on how wide the room is, um, and depending on the texture on the floor and how-- the texture on the ceiling and how much stuff is blocking everything else. I'll take five or six photos moving like this. So that's the outer pass, and I'll go around the entire room. Dun, dun, dun, dun, dun, dun, dun, dun, dun. That usually can take, like, five to ten minutes, depending on the size of the room. And dun, dun, dun, dun, dun, dun, dun, dun, dun, dun, dun, dun. You come back.
Handling Obstacles and Furniture
If there's something that you can't hug the wall, then you just keep your back to that thing. Um, depending on the context, I might hold the camera up above the thing, dun, dun, dun, dun, dun, dun, dun, just to really stay as far back on the wall as possible.
Avoiding Changes in Scene Geometry
Um, over here there's a little, like, kind of floor couch that we've got going on, and I would probably just step on top of the floor couch. The challenging thing about stepping on top of the floor couch is that, um, it's gonna change the, um, shape of the wrinkles, and you've gotta have total consistency between all of your different photos. So I probably actually wouldn't touch the floor couch. I would just hold my phone above it and then go around, and then keep holding my phone above it.
Capturing the Center Ring Pass
Okay, so that's the outer ring. The inner ring, um, you wanna come, kind of make a... This is a relatively small room, but I would make a kind of two meter or maybe one meter diameter circle, just standing in the middle of the room aiming out. And this is going to show very similar things than the edge ring did, but it's showing it from a different viewpoint.
Connecting Different Passes Together
And this is gonna be really helpful as the glue to help the, um, photogrammetry algorithm make sense of the third pass that we're gonna do, which is details. So here I have a whole shelf full of beautiful things.
Why Detail Passes Matter
Now, the only photos that I would have taken of this shelf were from, like, back here, right when I was doing my first pass of the room, or for my second pass of my center ring. But there's a lot of cool stuff here, and I wanna get all that, and I wanna see behind every single object and make sure that it looks good from everywhere, that this vase is not melting into the wall, which often happens in photogrammetry.
Capturing Small Objects and Occluded Areas
So now I'm going to do a pass of this object, taking photos from the floor, dozens if not hundreds of photos of everything, so that nothing is being blocked by anything. Um, you know, we have this cute little clock that's blocking this candle holder, that's blocking this vase.
Preventing Objects From Melting Together
We wanna get right up in here, um, and capture all these details. The problem with doing these detail, um, kind of passes is that often the algorithm doesn't know how they relate to the rest of the space.
Creating Visual Bridges Between Passes
So after I capture a detail pass of, like, this object, I will then also take photos back, back, back, back, back, back, back to glue it, glue it back to both the center ring pass and, you know, when I was standing against the opposite wall.
Understanding Photogrammetry Limitations
Um, this is my process for capturing super high-res scans, and it sometimes works. It sometimes doesn't work. It works best when you don't have, um, super bright, blown-out windows. It works best if you have not a ton of glass, not a ton of mirrors, not a ton of shiny things. Um, photogrammetry has a ton of limitations, but it's really, really cool. And often I will still have to go back and clean up the meshes. Um, I like to do it in virtual reality, um, which I can talk about in another video. Uh, but, um, you can use Blender to clean up these scans and then retexture them later.