Change image within 1 refresh

Hi all,

I would like to change the displayed image within the current refresh.
Example : 2 frames ;
first = display is filled with RED
second = display is filled with GREEN

Now I would like to be able to change within 1 refresh (1 frame)
So the beam of the CRT monitor starts at the top-left of the screen. When the beam is at e.g. 1/3 of the display, I want to change the displayed image but do not want to wait untill the whole frame is created, I want the beam to change real-time, and from now on (1/3) till the end of the image (bottom right) the 2nd frame is already presented.

This would then result in a frame of which 1/3 is RED and the rest of the display is GREEN.

I hope you understand what I mean. If so, is this possible with Cg or CUDA or whatever :)

(I have a FX 4500 card, but this could be changed if necessary)

kind regards,

Ha, sounds like a C64 project…

In my understanding of the GPU video-out technology, there is only the possibility to make the buffer swap wait for vertical retrace. You cannot wait for any specific scanline nor query which scanline is rasterized currently. That goes for CUDA aswell as any other graphics lib (or their extensions).