Soft Sprites in GTIA modes

[José Pereira]

Hi.

The soft sprites has always code for masking done in Byte steps (8bit number) so in all GTIA modes what makes sense is that I can have them in 2pixels width multiples that is 1Byte (soft sprites and also gfxs), right?

Thanks.

[José Pereira]

P.s.- And of course that I know that they can only move horizontally 4bits that is 2colour clocks each time...

Edited February 6, 2017 by José Pereira

[popmilo]

Yes and yes

You can have width that is odd number of pixels, but it's not practical as you need to draw whole byte anyway.

[MaPa]

Yes and yes

You can have width that is odd number of pixels, but it's not practical as you need to draw whole byte anyway.

It IS practical.. you can have 1 more pixel if you are going to draw that byte anyway. For 4 pixels wide sprite you need to draw 3 bytes and for 5 pixels wide again 3 bytes. Only if you do special case that the sprite is at byte boundary you can skip drawing the last colum for speed but for general purposes it's not needed as you have to count with the worst case to fit in a frame for example.

[José Pereira]

But if it's an odd number like for example soft sprite is 3 GTIA pixels you still have it 2Bytes like if it was 4 GTIA pixels and when it moves horizontally to have the shifting you need in total how many? From my paper and pen if is odd then the next even bit number is the total.

Soft sprite, the shifting and total:

-> 2GTIA pixels=1Byte you need 2GTIA pixels/1Byte more that are 2Bytes in total;

but if...

-> 3GTIA pixels you only need 1GTIA pixel more and are still 4GTIA pixels/2Bytes in total;

 

If is 4GTIA pixels/2Bytes and 2GTIA pixels/1Byte shifting then 3Bytes in total. But if is 5pixels then is still 3Bytes in total.

 

And so on...

 

 

P.s.- This is similar to 2:1 ratio for the shifting if we have 8pixels wide is the same as if we have 9pixels, 16 same as 17 and so on...

The same is for the charmode and 8scanlines/1char tall needs 1more char for the vertical movement but if is 9scanlines it still is 2chars in total.

16scanlines/2chars total need 1char more that is 3chars verticall in total but if is 17scanlines it still is the same vertical 3chars and so on...

Edited February 7, 2017 by José Pereira

[José Pereira]

@MaPa posted the same as me while I was typing...