Friday, October 9, 2009

Photo-texturing with Streetview

One cool new thing about Sketchup (the 3D Modelling software I use to create 3D models of buildings for Google Earth) is that you can import photo textures from streetview imagery.

It's great in that you can get a complete section of building really easily, by just selecting a part of the photo and hitting "grab." It automatically pastes the photo section onto the side of the model, giving it the phototexture.

It bloody beats going out and taking photos of building walls, having to stand far away to get the whole section, and worrying about what people assume you're doing, especaily if those people are watching you from a security camera attached to the building you're trying to model. I was approached by the manager of McDonald's once when the employees noticed me taking photos of the walls of the building to paste on the model. According to him, the property was private and no one, for any reason at all, no matter where they were in the vicinity of the building, could take photos (this included the scenario that if someone were taking a casual photo of someone else in the parking lot nearby and McDonald's showed up in the background, it would violate the privacy). Stupid.

The advantage of taking sections of imagery from Google Streetview is what I described above, but also the vantage point. It's far enough away on a street, and it's high above traffic and obstacles like bushes and people and stuff, so you can get something without parked cars in the way (mostly). The only unavoidable obstacles are trees and poles, or people or things stacked right against the wall.

The one big disadvantage is coverage. Up until yesterday Ottawa wasn't covered with streetview imagery, and now it is. However, I'm referring to the fact that these images are taken from the street and remain taken from the street.

For instance, I've tried texturing Merivale High School, because it's something I've been trying to do for about two years now, maybe three. I tried first with my original digital camera, and got really distorted, awful images that were taken too close and were too bright or blocked. One wall showed up as nothing but green as trees were in front of it. I was too close to the building, my images weren't big enough and the color was off by a lot.

Now, using Streetview imagery, the process took maybe thirty seconds to make a selection in the image taken convieniently across the road, and hit 'grab.' The images didn't look distorted, the color was good and it just looked right and had a lot less obstacles.

But the disadvantages I'm getting at is the fact that images are only taken at the street. I can't pull an image of the back of the building off of Streetview imagery because there's too many trees, it's too far away and it's just not there. The car didn't enter the driveway that runs around the building as it's private, so no imagery could be taken there (it would have been too close anyway). That's the big disadvantage of Streetview imagery. You can't do your house and pull an image of the back of the house off of it because a Streetview car didn't drive into your backyard to take the photo.

That disadvantage is both a great thing and an awful thing. The great thing about it is much more important. The great thing is that the reason the car didn't go there is exactly because of privacy. No way would you want your backyard to show up on Google Streetview on the Internet. Taking images of houses on residential streets is already kind of risky because people could have left their curtains open for the camera to get a clear shot of the interior of their house. If you have a corner lot and your fence is a simple chain-link type, and you have a pool, you wouldn't want a streetview car to drive by on the street while you were taking a dip. A month later and your colleague or friend tells you he saw an image of you in a swim suit in your backyard, courtesy of Google.

So while it's great that you can pull an image off of Streetview to help to build a 3D Model of the building you're doing, it's also good to respect the fact that you can't get everything, because streetview cars can't take photos of everything. They're limited to the street, which is a good thing. Getting the photo of the back yourself is probably the only thing to do, and it also means your decision to decide whether you want to take that photo and use it for your model.

I'm quite happy now that I don't have to go downtown to take very hard to get photos of tall buildings. But I also know and respect that I can only get so much, and that's that.

-Justin C. 

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