when I render an image larger than my screen, using OPENGL, I always seem to get a line half way through the image where there are some objects (circles for instance) that are somewhat transparent. I don't have this issue when I use JAVA2D or P2D and the image is larger than my screen. But I do have this issue when I use a Tiler (for instance  http://processing.org/discourse/yabb2/YaBB.pl?num=1248245155/0#11). And the line still appears half way of the image, not at the edges of the tile for instance. And of course, nowhere in my code do I draw a line, so it seems to be a side effect of using OPENGL and a large image?

Any idea what causes this, and more importantly, how to solve this?

I have placed an enlarged image of a fragment where this line appears on:  http://janwillemtulp.com/opengllineissue.png

I am using VerletPhysics from Toxiclibs to create a particle system. For each particle I use a spring that is attached to a fixed point (a locked particle), so that all particles are attracted to this point. At the same time I use a VerletMinDistanceSpring for all the particles to give the particles a minimum distance from each other. When I click the mouse, new particles are added, and the result works nicely and the particles are nicely stabilizing in a somewhat circular form around this target point. This is what I want to achieve.

However, it is not very effective to have a spring between all of the particles of course. I notice that at around 200 particles things start to slow down. 

I have tried various things, like adding and removing springs if particles are a certain distance apart. Drawing to an offscreen buffer (PGraphics), etc. 

But I haven't found a good solution to working with many particles this way yet. So, has anyone a good suggestion for a strategy for this situation? In short, I want to optimize my code by not having each particle have a spring connection to every other particle, while still make sure it has at least a spring connection to the target point, and also to the minimal required number of particles to maintain a 'force-directed layout'.

Thanks!

I was wondering, if I have an OPENGL sketch with 3D, would it be possible to have multiple camera positions in the same image? 

For example: I put a circle in the center and rotate a bit. Now, with the default camera settings you see the circle in perspective. If I would want the same circle with the same rotation and perspective translated to the right, next to the original one, would that be possible? 

I would assume that if this would be possible it would involve moving the camera and the frustum, but I'm not sure if this is possible... 

Any ideas?