Piddled around today a bit more & got my gaze point display to be a heat map. Not sure how these things are made, so I made it up as I went. First, I took every point that the eye tracker recorded and put it into a big 2d array based on its screen position. If a point was already there, I just added one to the count at that cell.
Then, I go through that array point by point. If a cell has at least one point I add to that point all the cells that are in a 20 point radius, weighting each point’s contribution with a Gaussian distribution based on the distance of the sample from the point in question. I then find the maximum count for the array. Each point drawn is then assigned a color based on its percentage of the maximum from blue –> green –> yellow –> red with shades in between. The warmer colors indicate that that area received a higher percentage of attention.