Frame interpolation?

[rain_storm]

How would you go about interpolating inbetween frames from a before and after? Best I can think of would be to choose a pixel, take the colour before add the colour after and average the two to create an inbetween. Is there a better solution?

[benny!]

You could also take the surrounding pixel colours into account (giving them a lesser weight) - but generally I am agreeing with you!

[Jim]

You can get lots of inbetween frames too.
Say you have a number between 0 and 1, where 0 means entirely the previous frame, and 1 means entirely the next frame, and anything in between is a blend of some sort, then you can get

Code: [Select]

'pseudo code
r0,g0,b0 = pixel from previous frame
r1,g1,b1 = pixel from next frame
f = blend_factor_between_0_and_1
r = r0 + f * (r1 - r0)
g = g0 + f * (g1 - g0)
b = b0 + f * (b1 - b0)

But, exactly as you say, a 50:50 blend can be done like

Code: [Select]

r = (r0+r1)/2
g = (g0+g1)/2
b = (b0+b1)/2
which is a smidge simpler to compute

Jim

[hellfire]

If you want a more convincing approach (and have plenty of cpu cycles to share) you could take the direction of motion into account.
For a start you could try to calculate blockwise motion vectors using autocorrelation (see eg block motion compensation).

[rain_storm]

Thanks guys. That bock motion compensation looks like it's worth trying out. I hear that lag is a problem with interpolation so you cannot boost a low framerate from 12 fps to 24, but when you're talking about demos lag is hardly an issue. At speeds of 30 fps the lag would be barely noticable.

[rain_storm]

merely interpolating the colours by taking the average works well, but only if the framerate is already high enough (say 25fps being boosted to 50fps). When the camera stops moving the effect disappears but when the scene is in motion it helps greatly to keep things greasy fast.

[benny!]

Looking good!