frencholdbuckhead

I'm trying to come up with a good way to filter the results from a grid of points that you calculate Optical Flow on.

The results from a point go a bit crazy when there is not a good feature to track (empty space, no detail and just some camera noise) and gives odd results, so you need to filter out the stuff you don't want from the stuff you want.

(Finding good features to track seems to be pretty slow (finding corners and the like) so it's not something you want to do every frame, but this is worth looking into again.)

Previously I was trying to do this by comparing the points position against a motion image, the idea being that if something is moving, I'm probably interested in it. But of course that relies on getting a good motion image to use, which can be a bit hard under the best of conditions (if a crowd is in front of the camera for instance), under low light conditions it gets even harder, while optical flow actually still works rather well.

Here I'm trying to do it by comparing the direction vectors with the neighbouring ones and turning off points that don't have a lot of similar neighbours.

Simple stuff really, but it wasn't working very well when I tried it the last time, so here I've resorted to drawing the number of similar neighbours and the angle of the vector, taking a screenshot and having a look in Photoshop.

Good sanity check, but I should have spent more time looking at the code as it was a pretty dumb indexing error in the end.

Update: This method worked really well in end, relatively dark environment and it stayed responsive. One problem is that if you move too fast it won't really do what you want, but people seemed to catch on easily enough, they were not the usual demographic (young people who could even take a fair stab at what algorithms the piece might be using) so that's encouraging. Not sure if it has to do with blur or what, perhaps running at 60 fps would help, but I didn't have a camera that could do it at hand.

B+W MRC UV filters (F-Pro or XS-Pro, various sizes, on all lenses)
B+W Kasemann CPL (Slim: 82mm and 77mm)
B+W ND filters (77mm: #103/0.9 and #110/3.0, 72mm: #103/0.9)
B+W Step-Up Rings (67>77mm and 72>77mm)
Canon Eg-S Super Precision Matte Focusing Screen
Canon Angle Finder C