SpritesMind.Net

This is video of my TV. Unfortunately I cannot put my bin file because it runs only with my cartridge.

https://www.youtube.com/watch?v=TwGmg6S00_k

It's a demo rendering and I would like to ask the community to decide is it blocking or not for your perception:

As you can see there are 5 vertical columns of double pixels.
It's impossible to remove them.
Is it OK for you to see them in a game or it's too annoying and you will not be able to play such game having such artifacts?

Thanks a lot guys!

Is this the color DMA stuff ? your image seems very colorful and the vertical enlargement stuff is similar to what we obtain with the background color DMA effect. For me the artifact is a bit annoying but not so much...

Yes that's it.
The direct color DMA injection in CRAM.
As far I know it was invented by Jorge Nuno. At least in our era.
I have read that someone in the Sega era made this trick but it didn't find any realization. Maybe because of these refraction column-artifacts.

However I used Chilly Willy implementation because have not ever seen Jorge's one.

Are you recreating StarCraft for the sega genesis?

BroOfTheSun wrote:Are you recreating StarCraft for the sega genesis?

No that's just a screenshot taken from StarCraft to demonstrate the artifacts.

However I work on an isometric RTS. Which (of course) resembles StarCraft a bit. But not as much as any other isometric RTS.

Steve Snake made the frist CRAM DMA demo.

Those artifacts are impossible to remove, at best you can render your image in a way you compensate the GFX itself to make the articats less noticable.

greatkreator wrote:Is it OK for you to see them in a game or it's too annoying and you will not be able to play such game having such artifacts?

This largely depends on what the gameplay is going to look like, but if you want my opinion, the columns would be annoying. They would make the game look broken.

It's not that I'd be unwilling to play such game. It's a matter of aesthetics. It's not one column, it's five. They seriously impact the visual appeal.

thanks a lot guys for your help and participation!
I think the same as Morden.
It's ok for some fun but in my opinion unfortunately rather not suitable for a serious product than suitable.
Very sad that Sega didn't make possibility to render RGB array directly to video output in a normal way.

However I find it enough suitable for static images and videos with up to 512 colors.

I'm sorry but the video is very blurred. What am I supposed to see good and bad ?

And what is this CRAM DMA trick ?

tryphon wrote:I'm sorry but the video is very blurred. What am I supposed to see good and bad ?

And what is this CRAM DMA trick ?

Sorry for a phone camera. it is crabby.
Even the blur of a phone camera cannot hide the artifacts.
You should have seen them. 5 vertical columns of doubled pixels.

The trick is called "direct color DMA".
You make a synchronized DMA to CRAM (into the background color).
In fact you put RGB array of 9-bit values directly on the screen.
You get visible 160x224 resolution of 2x1 pixels.
But it has a severe drawback: 5 vertical columns of doubled pixels looking like a refraction effect.
As well it has another drawback: it took all the non-vblank time because DMA halts Motorola 68000.

You don't have to be sorry. I have a netbook and weak eyes, it doesn't help either I think I've seen the columns, but not sure (there's one that goes through the left structure ?)

Interesting. How does it work eaxctly (a link is sufficient) ?

And what causes the doubled columns ?

TmEE co.(TM) wrote:Steve Snake made the frist CRAM DMA demo.

Actually, there are some words from a former Sega producer in Genesis Collective Works implying that the "blast processing" term was invented after seeing an internal demo using a DMA trick, which, done "at exactly the right time", let you "blast data onto the bus as as the video chip is reading a scanline" (sic) .

The reason it never was used is likely because it's only useful for slideshows and not suitable for real games since it eats quite all your available CPU time and RAM size.

tryphon wrote:You don't have to be sorry. I have a netbook and weak eyes, it doesn't help either I think I've seen the columns, but not sure (there's one that goes through the left structure ?)

Interesting. How does it work eaxctly (a link is sufficient) ?

And what causes the doubled columns ?

Search this forum DMA direct color. Chilly Willy author.

Some VDP thenical internals. As far I understand they called: "refresh pixels".
In that trick DMA can update its info for each 2 pixel (literaly is able to get new info from CRAM) and in the refresh pixels it slows down to 4 pixels for some unknown to me reason.

Eke wrote:

TmEE co.(TM) wrote:Steve Snake made the frist CRAM DMA demo.

Actually, there are some words from a former Sega producer in Genesis Collective Works implying that the "blast processing" term was invented after seeing an internal demo using a DMA trick, which, done "at exactly the right time", let you "blast data onto the bus as as the video chip is reading a scanline" (sic) .

The reason it never was used is likely because it's only useful for slideshows and not suitable for real games since it eats quite all your available CPU time and RAM size.

Eaten all cpu and ram are not a big problem.
The real problem are those 4-pixel-wide-column-refraction artifacts.
It's very hard to imagine a professional game having such artifacts.
It's not acceptable.