VBXE blitter : transparency?

[Thelen]

Hi, Back with another VBXE question... ? How can I do a blitter and use color 0 (black first of pallette #000000) as transparent?

I did some tweaking with the BLT_AND_MASK & BLT_XOR_MASK bytes in a blitblock (byte 16&17) but can't get something with color 0 to be transparent over the already drawed vram..

 

Thanks

[phaeron]

Use blit mode 1 instead of mode 0 -- it skips source bytes that are $00 after the AND/XOR.

 

[Heaven/TQA]

47 minutes ago, Thelen said:

Hi, Back with another VBXE question... ? How can I do a blitter and use color 0 (black first of pallette #000000) as transparent?

I did some tweaking with the BLT_AND_MASK & BLT_XOR_MASK bytes in a blitblock (byte 16&17) but can't get something with color 0 to be transparent over the already drawed vram..

 

Thanks

I suggest reading the Altirra Hardware reference manual or the VBXE manual… ?

[Thelen]

I tried reading the VBXE manual about the AND/XOR mask, but that didn't explain a lot about it, especially for a 'not' that much programmer like I am... ? Probably I'm doing something wrong.. But I will check the Altirrra reference about it later ?

Edited May 23, 2022 by Thelen

[+Stephen]

There's also the VC (Video Control) register - bit 2 controls the "no-trans" register.  But the VBXE manual says that does not have an effect on the blitter (page 40).  I've only done some very simple blitter code in text & graphics modes, but just using mode0 for direct copying.

 

Nice to see someone else coding for VBXE - may I ask what you are doing currently?

[Thelen]

21 hours ago, phaeron said:

Use blit mode 1 instead of mode 0 -- it skips source bytes that are $00 after the AND/XOR.

 

Thanks, that did it ?

 

 

17 hours ago, Stephen said:

There's also the VC (Video Control) register - bit 2 controls the "no-trans" register.  But the VBXE manual says that does not have an effect on the blitter (page 40).  I've only done some very simple blitter code in text & graphics modes, but just using mode0 for direct copying.

 

Nice to see someone else coding for VBXE - may I ask what you are doing currently?

Also thanks for that! Currently I'm making a Castlevania port, codename CastleAtaria ?.... For now the game scrolls and the player can walk, every week I make some progress. I don't know for how long I will work on it and can stay motivated enough ?

So far as it's programmed now I can use the code either for another sidescrolling game (like Super Mario or Ducktales where I also was doubting/thinking about to work on)- but like alway's there are a lot of ideas and too less time. I wanted also to easily design levels, so it can use output of the 'Tiled' software (and then convert that with a little Python code).

Just for the impression a little video...therandom pixels on top of the screen are there because there is nothing yet, it for the score etc.