
Show HN: Street View Simple – Explore Street View Data in a Browser - callumprentice
https://callumprentice.github.io/apps/street_cloud_simple/
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jefft255
That's doesn't properly look like lidar data to me; at least it wouldn't be
lidar that is mounted right on the street view car. Maybe they use aerial
lidar somehow? Or maybe the resolution is purposefully poor?

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sdan
Yeah, this definitely doesn't look like lidar data... unless its really low
quality. The buildings show spatial depth, but the cars and pedestrians are
pretty much all in a circle (they have no depth).

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mthoms
I don't know much about lidar but.. is it possible Google have done this
intentionally with some sort of algorithm? After all, pedestrians and vehicles
are just "noise" in the context of mapping/visualising streets.

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saeranv
This seems really cool, but I don't quite understand what I'm looking at. Is
this a processed version of the LIDAR data for the environment?

Also why do the "pixels" get less dense at the edges of the view? I.e as you
rotate, the pixels that were previously at the center of the screen get more
sparse as they reach the edges of your view? My intuition is that if you
sample points on a hemisphere equally (a difficult task in of itself), then
you shouldn't get this kind of pixelation. So is there something going on here
with either the orientation of the squares, or sampling that causes the
density/exposure to fall-off with cosine of the vector looking ahead and
vector to the side?

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callumprentice
Yep - there is way to grab the depth data from each Street View pano along
with the image data. I plot each point 3D space and grab the corresponding
color from the image. The separation is uneven - depends on what the the depth
camera sees I guess - many of the points are marked as off at infinity.

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saeranv
Interesting, so it's the data they provide that is sparse. If you expand the
view to full screen, and stare straight-on at the wall, you can clearly see
the 'sparse' pixels form a circle around the camera on the ground and at the
sky.

I don't really know how LIDAR works, so I don't know if it's something
intrinsic to the process, or a decision made by the engineers.

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callumprentice
Yah, I've noticed that too - I wondered if it was an. artifact of the way I
render the points but since the building look mostly right, I figured that was
the way it is.

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saeranv
That's a possibility. Are you rotating your squares in just the xy plane, or
also along the "pitch"?

I find your project fascinating, thank you for sharing it!

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callumprentice
Thank you so much. I use the built in point cloud primitive which I think is a
list of billboards geometry and all you can change is the size of each point.

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saeranv
Okay, so it has nothing to do with the orientation of the point planes.

Having thought about it some more, I think this is a consequence of the
reduction of surface area hit by the LIDAR rays, as the square of it's
distance. Basically, the rays are cast in a spherical distribution (which has
a surface area of 4 _pi_ r^2). So the further out you go, the rays "capture"
less of the environment, and you get the sort of sparse pixels at a distance.

So those circles are just reductions in pixel density that are proportional to
linear distance from the center of the LIDAR sphere. You can kind of see how
depending on the distance to the building walls, the surrounding 'halo' of
circular pixel density increases or decreases.

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callumprentice
Nice! I noticed that halo effect you mentioned - fascinating to get some
background. Thanks for taking the time to post.

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kevinali3
Is there any software (preferably open source) that can be used to build one's
own street views for areas/countries that are not covered by Google?

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windthrown
The software is not open-source but both Mapillary and OpenStreetCam have very
permissive licenses. I contribute to and use both services to improve
OpenStreetMap.

Mapillary: [https://www.mapillary.com/](https://www.mapillary.com/)

OpenStreetCam: [https://openstreetcam.org/](https://openstreetcam.org/)

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Mediterraneo10
OpenStreetCam itself isn’t quite closed-source: it is on Github. But the app
was built on top of Facebook tools, which many people will not want on their
phones. See the notorious outstanding Github issue [0]. At least OSC’s hard
dependency on Google Play Services appears to have been removed, though – last
time I looked into installing Mapillary, it still would not run on a bare
Android like LineageOS.

[0]
[https://github.com/openstreetcam/android/issues/8](https://github.com/openstreetcam/android/issues/8)

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pj_mukh
This is very cool! I'm thinking the depth data that is captured is of higher
resolution. Is that true? Was this limited by the API? Or a limitation of the
browser?

Super cool to see this depth data IRL.

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callumprentice
Thank you! As far as I know (it's undocumented) the only source of depth data
is very low resolution. The image data (where the color of each point comes
from) is much, much higher - shame they're not on par with each other.

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moron4hire
I've been very interested in getting access to the depth data for a VR project
I'm working on. Is this something you could talk more about, perhaps over
email (in my profile)?

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callumprentice
Yes of course - email sent - I spoke too soon - message was blocked for
unspecified reasons. My email is my profile if you'd like to start a
conversation.

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00deadbeef
I’ve got no idea what this is. The text on the page is truncated in Safari on
iOS so I assume there are some explanatory notes I can’t see?

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raimue
Even with the full text I do not understand what I am seeing. The comparison
to previous projects did not help because I do not know them either.

It appears to be a different rendering of the Street View data that will be
loaded from Google servers. What is the purpose of this site? Just to show how
Street View works internally?

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saeranv
Looking at this makes me wonder how Google combines the point data to generate
clean polygons. I.e when I hover my mouse over a wall in Street View, it
identifies correctly the entire connected plane.

Does anyone know how this is done?

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callumprentice
I'd like to know that too - all kinds of neat things are possible when you
have polygons vs points.

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thepete2
Does not work in firefox...

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callumprentice
Oh no! I don't think there is a reason it won't - I'll grab Firefox and see if
I can fix it now.

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callumprentice
I just grabbed the latest version for macOS (77.0) and it works okay there?
Which platform are you seeing it fail on?

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ciarannolan
Works for me on the latest versions of MacOS and Firefox :)

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callumprentice
Thanks!

