Collectif Ascidiacea

I'm a casual user of max and I've been working on a new project that implies finding the position of a laser through the webcam. It's been working great so far, but I still have a little trouble getting only the position of the light since it's live video and there is often a lot of noise in it. So my idea was basically creating a mask to hide all the parts that I don't need from the cam and focus only on a small rectangle where the laser should be.

That's where the real trouble starts : no matter how big or small are the mask and the visible area, jit.findbounds (which i use for finding the laser point) doesn't output a single value from the moment I use jit.alphablend before.

Since I'm a bit of a newbie, I thought I missed something, but I've been trying all sort of things for two days and found no workaround. Here's a bit of code that should demonstrate how it (is supposed) to work :

(you can find it as attachment, I tried to include it in text format but that didn't work, probably too long)

I included some objects in the "findbounds" subpatcher to find the center of the area and apply a "tolerance" filter to close the output when it is too big, but you can see even before that there's no output at all.

I hope someone can help me here, I'll be very grateful if that's the case.

trouble-getting-jit-alphablend-to-work-with-jit-findbounds

Sorry, this first patch was a real mess, I cleaned it a little bit and used xfade to show the issue in a much simpler way. I'm attaching it to this message.

Aaaand I also figured the cam part could be a problem for you if you want to test it, so I made another version with a video source from the tutorial examples. I'm including it in this last message.

Sorry for the many posts, hope this way it will be easier if someone wants to have a look at it.

you need to set the @min color values to something slightly higher than 0. otherwise it's tracking the black area and giving you the bounds of the entire window.

Did you try that ? I felt dumb as hell reading you, but unfortunately I just tried a few other values and it doesn't seem to change anything... And I'm also wondering, since I was using the "countdown" example movie, there was already lots of black pixels on that picture and it shouldn't have made such a difference adding a black mask I guess.

If you can find some working values in my example, could you show me ?

Well it's becoming weirder and weirder... I was still trying to figure it out and somehow it started working !! So I checked what I could have done different, and apart from trying again and again to connect it all differently before ending where I started, nothing special. So I saved it, hoping it would work again when I reopen it. It didn't. :/

Here's an even simpler patcher without anything useless that shows that jit.alphablend prevents jit.findbounds from findind anything. Maybe it adds some kind of data to the matrix that jit.findbounds can't understand ?

I FOUND OUT !! As I thought it was really a dumb thing actually, jit.alphablend just needded an input in the right outlet. I just sent the mask matrix in it and it works now. Not sure I get why, but that does the job.

Thanks Rob for trying to help, now I'm getting back to the main project and I hope if anyone has a similar problem they will find the answer right here.

Trouble getting jit.alphablend to work with jit.findbounds