More Than Technical

Posts Tagged ‘3d’

Hi

Just wanted to share a small thing I did with OpenCV – Head Pose Estimation (sometimes known as Gaze Direction Estimation). Many people try to achieve this and there are a ton of papers covering it, including a recent overview of almost all known methods.

I implemented a very quick & dirty solution based on OpenCV’s internal methods that produced surprising results (I expected it to fail), so I decided to share. It is based on 3D-2D point correspondence and then fitting of the points to the 3D model. OpenCV provides a magical method – solvePnP – that does this, given some calibration parameters that I completely disregarded.

Here’s how it’s done

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Hi

Been working hard at a project for school the past month, implementing one of the more interesting works I’ve seen in the AR arena: Parallel Tracking and Mapping (PTAM) [PDF]. This is a work by George Klein [homepage] and David Murray from Oxford university, presented in ISMAR 2007.

When I first saw it on youtube [link] I immediately saw the immense potential – mobile markerless augmented reality. I thought I should get to know this work a bit more closely, so I chose to implement it as a part of advanced computer vision course, given by Dr. Lior Wolf [link] at TAU.

The work is very extensive, and clearly is a result of deep research in the field, so I set to achieve a few selected features: Stereo initialization, Tracking, and small map upkeeping. I chose not to implement relocalization and full map handling.

This post is kind of a tutorial for 3D reconstruction with OpenCV 2.0. I will show practical use of the functions in cvtriangulation.cpp, which are not documented and in fact incomplete. Furthermore I’ll show how to easily combine OpenCV and OpenGL for 3D augmentations, a thing which is only briefly described in the docs or online.

Here are the step I took and things I learned in the process of implementing the work.

Update: A nice patch by yazor fixes the video mismatching – thanks! and also a nice application by Zentium called “iKat” is doing some kick-ass mobile markerless augmented reality.
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Hi everyone

In the last weekend I attended GeekCon 2009, a tech-conference, with a friend and colleague Arnon (not Arnon from the blog, who recently had a birthday – Happy B-Day Arnon!). Each team that attended had to create a project they can complete in 2-days of the conference. Our project is called “RunVas”, and the basic idea was to let people run around and paint by doing so. We wanted to combine computer vision with a little artistic angle.

Here’s some more details
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Hi

The graphics course I took at TAU really expanded my knowledge of 3D rendering, and specifically using OpenGL to do so. The final task of the course, aside from the exam, was to write a 3D game. We were given 3 choices for types of games: worms-like, xonix-like and lightcycle-like. We chose to write our version of Worms in 3D.

I’ll try to take you through some of the problems we encountered, the decisions we made, and show as much code as possible. I’m not, however, gonna take you through the simple (yet grueling) work of actually showing meshes to the screen or moving them around, these subjects are covered extensively online.

The whole game is implemented in Java using JOGL and SWT for 3D rendering. The code is of course available entirely online.

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Hi

I saw the stats for the blog a while ago and it seems that the augmented reality topic is hot! 400 clicks/day, that’s awesome!

So I wanted to share with you my latest development in this field – cross compiling the AR app to the iPhone. A job that proved easier than I originally thought, although it took a while to get it working smoothly.

Basically all I did was take NyARToolkit, compile it for armv6 arch, combine it with Norio Namura’s iPhone camera video feed code, slap on some simple OpenGL ES rendering, and bam – Augmented Reality on the iPhone.

Update: Apple officially supports camera video pixel buffers in iOS 4.x using AVFoundation, here’s sample code from Apple developer.

This is how I did it…
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Hi

I have been playing around with NyARToolkit’s CPP implementation in the last week, and I got some nice results. I tried to keep it as “casual” as I could and not get into the crevices of every library, instead, I wanted to get results and fast.

First, NyARToolkit is a derivative of the wonderful ARToolkit by the talented people @ HIT Lab NZ & HIT Lab Uni of Washington. NyARToolkit however was ported to many other different platforms, like Java, C# and even Flash (Papervision3D?), and in the process making it object oriented, instead of ARToolkit procedural approach. NyARToolkit have made a great job, so I decided to build from there.

NyART don’t provide any video capturing, and no 3D rendering in their CPP implementation (they do in the other ports), so I set out to build it on my own. OpenCV is like a second language to me, so I decided to take its video grabbing mechanism wrapper for Win32. For 3D rendering I used the straightforward GLUT library which does an excellent job ridding the programmer from all the Win#@$#@ API mumbo-jumbo-CreateWindowEx crap.

So let’s dive in….
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Hi

I havn’t published in a while. I was back up with work on a project for uni., work and my writing…

But the good thing with keeping busy, is that after a while – you have something to show for! So here’s what i’ve been working on for Comp. Graphics course – A Ray Tracer.

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Hi

I had a little project at work recently, that involved creating movie clips using AviSynth.
And I was appalled by the shabbiness of existing transition plugins available freely for AviSynth, they always reminded me of 80s-like video editing…
So I set out to integrate AviSynth with OpenGL to create a nice 3D transition effect for our movie clips.

I had 2 major bases to cover:

• AviSynth plugin API
• OpenGL rendering

AviSynth API is not so well documented, but they have very good ground-up examples on how to DIY plugin. Here is the one I used, that basically does nothing but copy the input frame to the output frame.
Open GL on the other hand is very well documented and “tutorialed”. I based my code on this example from NeHe.

So basically what I wanted to achive is:

1. Read input frame (AviSynth)
2. Paint frame as texture over 3D model (OpenGL)
3. Draw rendered 3D image to output frame (OpenGL+AviSynth)

Reading the frame is pretty straightforward. Frames come encoded as RGB 24bit, with a little twist: rows size in bytes is not width*3 as you’d expect it be, but AviSynth use a parameter called “Pitch” to determine row size in bytes.

Update (14/9/09): source is now available in the repo: browse download
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