NEHE tutorial 11 covers a sin wave flag effect in OpenGL, in theory you should be able to get this to work in BlitzMax under the OpenGL drivers.
But there is probably a nice pixel/vertex shader version somewhere that might work better with the the modern GPU's, only your moving out of BlitzMax's current feature set then.
Although a simple pregenerated animation using pixmaps->images would probably work better... all you would have to do is copy the image pixel by pixel with a waved based x (or y) offset for each line and repeat offsetting the effect until a full animation cycle is created, in theory!
But there is probably a nice pixel/vertex shader version somewhere that might work better with the the modern GPU's, only your moving out of BlitzMax's current feature set then.
Although a simple pregenerated animation using pixmaps->images would probably work better... all you would have to do is copy the image pixel by pixel with a waved based x (or y) offset for each line and repeat offsetting the effect until a full animation cycle is created, in theory!