Re: A89: Re: Re: Survey for the next version of PlusShell
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Re: A89: Re: Re: Survey for the next version of PlusShell
That's a good idea, but you're still going to have those three cases unless
you rewrite findpixel to handle negative numbers. It would probably be
easier not to and doing so wouldn't improve speed. It might be worth it,
though, if you had some intensive vertical side scrolling.
>
>What do you say about my idea to move tha screen a bit in the graph-mem,
and
>then get rid of the need for clipping at _all_ sides
>
>//Olle
>
>Dux Gregis wrote:
>>
>> >>
>> >>At 20:46 1998-11-18 -0500, you wrote:
>> >>>On the 89 LCD, a sprite must be clipped only when it crosses the top
or
>> >left
>> >>>side LCD edges.
>> >>
>> >>Not really true... a sprite on the top row, with a negative x value
>> >>(x=-8,y=0) would in that case start writing before the video memory
>> >>starts... so a special case is needed with such sprites.
>> >
>> >That's what I meant: the two special cases are at the top and left side
of
>> >the screen. It's also a good idea to not put the sprite when it is
>> >completely off the screen in either of the other two directions,
although
>> >that would not really constitute clipping.
>>
>> Let me revise that: there are actually three cases, the third being that
>> _both_ coordinates are of negative values. In some clipping routines,
this
>> must be treated as a unique case. (Really; before I implemented that
case
>> in the 89 clipping routine I wrote, it actually crashed the calc when you
>> tried to move the sprite off both the top and the left edges of the
screen
>> simultaneously) This is very nice because on all other TI calcs there are
>> eight cases you must implement! (or at least test)