chris

mod gives you the remainder of a division, so by mod’ing the y coordinate by 1.5, I’ll always get a number between 0 (when it divides exactly) and 1.5 (when it doesn’t).

So when I multiply that temp variable by the actual r,g,b in the image, I scale the colors from black (0,0,0) to over bright (more than white) (1.5, 1.5, 1.5) which gives it more of a TV look. You won’t actually see anything more than white, but for dark images you’ll notice them looking brighter than they should be.

Adding the lineSize scale factor was just showing how you could add a parameter to make the filter more dynamic. I don’t think it is very satisfying for animation, but you could use it to tune a look that you wanted. I just wanted to keep it simple.

One thing you’ll notice is that you get this kind of gradient effect from black to bright and then right back to black. Instead of using mod, you could use sin or cos to get more of a smooth look.

Thanks. I was trying to figure out how to do that last night.

Can you explain what you are doing?

float temp = mod(outCoord().y, 1.5 * lineSize);
dst = dst * float4( temp, temp, temp, 1.0 );

mike

kernel ScanLines

{
input image4 src;
output pixel4 dst;
parameter float lineSize;

void
evaluatePixel()
{
//get the current pixel
dst = sampleNearest(src, outCoord());

float temp = mod(outCoord().y, 1.5 * lineSize);
dst = dst * float4( temp, temp, temp, 1.0 );
}
}

btw funny coincidence – my first pixelbender-experiment was TV-screen related as well :) http://www.flickr.com/photos/pixelero/2179760121/

I did a color keying filter some time ago:
http://www.video-flash.de/index/flash-player-10-pixel-bender-realtime-color-keying/