Emscripten Port

[Introvertuous]

I was wondering if there is any interest in a javascript port of this library through emscripten, or if that is something you guys have possibly looked into.

[AlejandroSilvestri]

Well, what's the point of that?

It easier to write code like this on MatLab, but it must be in C++ because C and C++ compile to very efficient code. Javascript is the opposite, it is very slow. ORB-SLAM2 on javascript could process 30 frames per year :)

[Introvertuous]

I suppose javascript does not necessarily have to be the compile target: http://webassembly.org/

[AlejandroSilvestri]

@Introvertuous , thank you, now I see what you meant.

It would be great to create a repo devoted to this goal.

Right now I prefer to know if that compiler can compile C++ with STL and opencv.

I believe emscripten can't use dependencies, you have to add all dependencies in one big project (including opencv, for example). I don't know if that is even possible.

[AlejandroSilvestri]

@Introvertuous, opencv now has opencv.js

https://docs.opencv.org/master/d5/d10/tutorial_js_root.html

One step closer to port ORB-SLAM2 to webassembly :)

[lukedukeus]

@Introvertuous Any update / progress on this?

[AlejandroSilvestri]

@lukedukeus ,

As far as I know, noone is working on this.

[nickw1]

Experimenting with getting ORB_SLAM3 working on emscripten.

See https://github.com/nickw1/ORB_SLAM3, this compiles on emscripten (the library, but not the examples which depend on opencv features not available in opencv.js)

Have started experimenting with creating an application using it, see https://github.com/nickw1/orb-slam-expts/

... it compiles, but loading the vocabulary is very slow, as in, more than 10 minutes (at which point I gave up), Maybe the file I/O in emscripten is too slow?

Would be interested if anyone has any hints for getting this working.

[AlejandroSilvestri]

@nickw1, that's great!

There are many binary implementation for vocabulary: voc file is smaller, and loads 100x faster.

I don't know any standalone project on binary voc, but many orb-slam2 forks implemented their own very similar binary voc.

My own is here, look for loadFromBinaryFile method to see how it is implemented on orb-slam2, and the binary voc file:

• loadFromBinaryFile
• https://github.com/AlejandroSilvestri/os1/blob/master/orbVoc.bin

[nickw1]

@AlejandroSilvestri thanks! As it happens that is precisely what I have been working on this morning, having discovered this late yesterday :-)

I found this one: https://github.com/surfii3z/ORB_SLAM3. Looks like this was originally done for ORB_SLAM2 and was ported to ORB_SLAM3.

Thanks for letting me know of your own implementation.

[nickw1]

@AlejandroSilvestri to follow up... with the binary file the vocabulary now loads successfully in 2 seconds on emscripten. Haven't tested whether tracking works yet. Thanks again!

[AlejandroSilvestri]

@nickw1

I am very interested in following up on your project. Please continue posting here or tell me where.

[nickw1]

@AlejandroSilvestri thanks.
The github repos are:
https://github.com/nickw1/orb-slam-expts/ (experiment to get ORB-SLAM working with emscripten)

and

https://github.com/nickw1/ORB_SLAM3 (my fork, the binvoc branch is the one to look at). If I have to update ORB_SLAM itself to get it to work, I will make commits here.

For both repos, I will keep a log of changes made, and experiments done, in the README.

[nickw1]

Sorry, typo in first repo, note it's https://github.com/nickw1/orb-slam-expts

[nickw1]

Making some progress on this. However, as soon as reconstruction with two views occurs, I get an unaligned memory access error. Emscripten can't handle unaligned memory access: is this something that ORB-SLAM3 is doing? @AlejandroSilvestri any ideas? Thanks.

Unfortunately the debugging from Emscripten can't pinpoint the actual line, so this will require more digging... but just wondered whether this was a known issue in ORB-SLAM3.

[nickw1]

Output from log:

*** CreateInitialMapMonocular() orb_wasm.js:2695:8
First KF:0; Map init KF:0 orb_wasm.js:2695:8
New Map created with 55 points orb_wasm.js:2695:8
Point distribution in KeyFrame: left-> 55 --- right-> 0 orb_wasm.js:2695:8
RuntimeError: unaligned memory access