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Originally Posted by ReadOnlyCat
That's actually what I understood. 
So for a strip which is distorted exactly diagonally you will have to proceed to 16 blitter copies of the original strip each copying only one column of the source... |
No, that's why i mention "sine-wave scroller technique". You don't need to copy each 1-pixel column individually, you need at most 4 blits for an arbitrary x-dependent distortion of up to 15 pixels. But these blits are only 16 pixels tall for a 16 pixel tall texture.
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In practice however perspective projection means that all lines of the strip must be distorted differently and on a y basis, so the distortion is a function of x and y and not just y.
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Yes, that is the point. You distort it one way at the top, and by the time you reach the bottom it's distorted the other way. But the entire strip will not be distorted on every line, only small parts of it will change, since there is only 16 pixels of vertical distortion of the strip over the entire height of the destination screen.