🚀 go-pugleaf

vanderby@mprgate.mpr.ca (David Vanderbyl) writes:

>eker@loria.fr (Steven Eker) writes:
>>If your frame redraw code takes longer than one video frame, one way of speeding
>>things up is to use triple buffering rather than double buffering.
>[explanation deleted]

>Triple buffering is completely useless. (Almost) Here's why.

>Let's say your screen redraw takes 0.9 of the frame rate time.
>No problem, right?  You simply draw each frame and wait for
>the vertical retrace.

>Now let's say your screen redraw takes 1.1 of the frame rate time.
>If the frame rate is 1/30 second per frame then your redraw takes
>1.1/30 of a second.  So in 1 second you need to draw 30 frames for
>a total of 1.1/30 * 30 = 1.1 seconds.  It doesn't matter how many
>buffers you use, you can't do 1.1 seconds worth of drawing in 1
>second.

Right, so using double buffering in your example, it takes 1.1/30 seconds
to draw the frame, which is longer than a single frame video refresh.
Note, you _cannot_ flip the page unless the video in inside a vertical 
refresh. In this case, it is not, and you will need to wait an extra
0.9/30 of a second waiting for the refresh to flip the page, which could
be spent redrawing the next frame in the third buffer. Think about it.

>To the person who posted their triple buffering idea:
>Please state that you idea is just that, an idea. (and in this
>case not a very good one.)  It will save a lot of people from
>being misled.

Could I please ask that people like you who like to express your
opinons on subjects, continue to do so in a manner that does not offend
anyone. It is very easy to _think_ you know the answer to a subject, but
it is quite possible that your answer is incorrect (MORAL: never take
anything anyone says at face value, always add that pinch of salt...)


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