Is there a way to create a lightning effect on the iPhone using opengl?(like this app)
Right now I have modified the glpaint sample to draw random points around a line (between two points that the user touches) and then connecting them, but the result is a zigzag line that constantly jumps around and lags horribly on the actual device.
you'll probably just want to make a triangle strip from the center of the device to the point that is being touched, then apply a drawn lightning texture to that resultant polygon.
You can animate the texture in order to get the jumping lightning effect.
A simple way to create a lightning effect is to compute the lightning path using a 2D Perlin function, rendering it to a glow buffer, blurring it with a Gaussian blur shader, and merging it with the scene. You can make the lightning move by computing two paths (start and end) with an identical number of path nodes and moving each node of the start path successively towards the corresponding node of the end path. Once the end path has been reached, it becomes the start path and a new end path is computed.