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Author Topic: VP.org: Advanced game graphics , part 1  (Read 1917 times)
Rene_G7400
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« on: September 17, 2007, 06:13:50 PM »

Advanced game graphics     
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al

Joined: 01 Oct 2006
Posts: 17
Location: Munich, Germany
   
Post Advanced game graphics    

Hi all,

I'm curious to learn which games make advanced use of the Videopac's graphic chip and go beyond standard grids, sprites and characters. Like inter-frame reconfiguration or undocumented VDC features. Frogger for instance, relies heavily on scan line timing and Tutankham does strange things to quad characters Shocked But which other games would line up here?

Reason for this query is that I'm currently working on a conversion of the Videopac system to FPGA which now turns to the gaming, err serious debugging phase Wink The final result will be similar to the projects hosted at http://www.fpgaarcade.com/ with open design sources.

Thu Dec 07, 2006 9:46 pm    


fernandotcl

Joined: 09 Nov 2006
Posts: 29

That's awesome.

Well, Power Lords!, Demon Attack, Shark Hunter and some screens in Turtles! come to mind.

Thu Dec 07, 2006 11:24 pm    


Rene_G7400

Joined: 06 Mar 2006
Posts: 651
Location: Netherlands

A few examples of games that do a lot of mid-screen graphics changes are:
4 in 1 row, Samurai (a.k.a. Dynasty), Type and Tell, Backgammon, Syracuse.

Sat Dec 09, 2006 11:11 pm       


al

Joined: 01 Oct 2006
Posts: 17
Location: Munich, Germany

Ok, I'll try these next.

Thanks a lot!

Sun Dec 10, 2006 3:28 pm    


VPR

Joined: 20 May 2005
Posts: 1164
Location: Warrington In the United Kingdom

ok...what does this mean in childish please ?

does this mean an odyssey on a chip...ie step closer to a handheld, plug in the tv all in one Magnavox Odyssey 2 ?

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Richard Page
www.videopac.org

Sun Dec 10, 2006 4:44 pm         


al

Joined: 01 Oct 2006
Posts: 17
Location: Munich, Germany

   VPR wrote:
   does this mean an odyssey on a chip...ie step closer to a handheld, plug in the tv all in one Magnavox Odyssey 2 ?


Yeah, right - an odyssey on a chip. The chip in this case is a general purpose FPGA (Field Programmable Gate Array), a huge "sea" of logic gates that is programmed with hardware description languages and appropriate compilers. Such an FPGA can be programmed to contain virtually any functionality you can find on standard chips, only constrained by space (like amount of logic resources) and speed. An Athlon with GHz speed just wouldn't fit into FPGAs today and they wouldn't deliver equal speed.
FPGAs have grown tremendously in the past - and the old 8-bit systems are not very complex. My current odyssey design for example requires roughly 1/4 of a mid range FPGA.

Typically, I develop this kind of stuff on prototype boards. They're flexibel but not very compact and rather expensive (the most simple ones start at around $100 and might be large enough). Once the project is finished and with the extra effort of a dedicated board, you would end up with just an FPGA, a flash memory for the code, some resistors, caps etc plus joystick, keyboard and video connectors. Pretty close to a "plug in the tv all in one Magnavox Odyssey 2".
When you look at the DTV64, it's nothing more. Just that the FPGA has been exchanged with a dedicated chip for cost reduction.

Sun Dec 10, 2006 7:34 pm    


VPR

Joined: 20 May 2005
Posts: 1164
Location: Warrington In the United Kingdom

fascinating, we were just discussing this, but thought although it would be of great intrest to enthusiasts, wouldnt realy be commercialy viable for the big companies.

is it tan fpga that these (built in the joystick) ataris use ?

and can one of these be adapted to an odyssey one ?

when youve got it all sussed out ?

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Richard Page
www.videopac.org

Mon Dec 11, 2006 11:03 am         


Odyssey3

Joined: 23 Nov 2006
Posts: 283
Location: (BOSTON U.S.A) NEW ENGLAND!
 
   fernandotcl wrote:
   That's awesome.

Well, Power Lords!, Demon Attack, Shark Hunter and some screens in Turtles! come to mind.
Dont forget "Flashpoint"and how about"Tutankham, maybe spiderman!!
<O3>

Tue Dec 12, 2006 4:20 am         


Rene_G7400

Joined: 06 Mar 2006
Posts: 651
Location: Netherlands

   Odyssey3 wrote:
   Dont forget "Flashpoint"and how about"Tutankham, maybe spiderman!!
<O3>


Flashpoint doesn't use the standard graphics video chip (except for a few sprites).

Tue Dec 12, 2006 10:13 am       


Odyssey3

Joined: 23 Nov 2006
Posts: 283
Location: (BOSTON U.S.A) NEW ENGLAND!

   Rene_G7400 wrote:
   Flashpoint doesn't use the standard graphics video chip (except for a few sprites).


opps.. forgot..

Tue Dec 12, 2006 4:25 pm         


al

Joined: 01 Oct 2006
Posts: 17
Location: Munich, Germany

   VPR wrote:
   is it tan fpga that these (built in the joystick) ataris use ?

I'd be surprised if yes. An FPGA would be quite expensive for mass production.

   VPR wrote:
   and can one of these be adapted to an odyssey one ?

Hacking such a stick - what a marvelous idea! Just can't wait to pick up a clone at local stores and rip it apart Razz Let's see what's inside...

Graphic debugging keeps me busy at the moment, and the sound is terribly noisy. It'll take another one or two weeks until the basic design is finished. Holiday season will hopefully allow more time...

Tue Dec 12, 2006 7:26 pm    


al

Joined: 01 Oct 2006
Posts: 17
Location: Munich, Germany

   Rene_G7400 wrote:
   A few examples of games that do a lot of mid-screen graphics changes are:
... Type and Tell ...

Did this have a dedicated PAL release or was it NTSC only? The copy I have relies on the NTSC style "instructions per line" and wouldn't work properly on PAL machines.

Wed Dec 13, 2006 10:39 pm    


Odyssey3

Joined: 23 Nov 2006
Posts: 283
Location: (BOSTON U.S.A) NEW ENGLAND!

   al wrote:
   Did this have a dedicated PAL release or was it NTSC only? The copy I have relies on the NTSC style "instructions per line" and wouldn't work properly on PAL machines.


i beleave Type-n-Tell was a U.S release only...O3

Thu Dec 14, 2006 12:48 am         


Rene_G7400

Joined: 06 Mar 2006
Posts: 651
Location: Netherlands

   Odyssey3 wrote:
   i beleave Type-n-Tell was a U.S release only...O3


It was NTSC only (The Voice wasn't released in Europe), but I have made a PAL version (with 7 lines of text instead of 6 ).

Thu Dec 14, 2006 7:57 am       


Kurt_Woloch

Joined: 08 Jun 2006
Posts: 13
Location: Vienna

OK, I think there's more games who do mid-screen rewrites.
I'll list the ones I can think of, along with the nature of the rewrites:

Puzzle Piece Panic (if it has been released already?) - rewrites the sprites to display the puzzle

Alien Invaders - Plus! - displays 3 rows of 8 aliens each, making for 24 sprites, so there must be some rewriting going on.

Atlantis - I'm not really sure about that, but I'm pretty sure that sprites get reused at least in the upper part where the enemy ships get displayed

Chess - probably also does rewrites to display all the pieces. Maybe that's part of the reason why they had to add a 2nd processor to do the move calculations while still displaying the picture.

Demon Attack - here you can see at least 2 aliens, each of which is multicolored and 16 pixels wide, which means that each of them consist of all 4 allowed redefinable sprites, so there must be rewrites between the two

Dynasty - has to have rewrites in order to display the whole playing field

Frogger - this has to do rewrites since each line of cars / logs consist of user-definable sprites.

P.T.Barnum's Acrobats - displaying 3 rows of 8 balls each + some men

Q*Bert - I'm pretty sure this reuses sprites too... if you look at the "cubetops" closely, you notice that they aren't made out of the grid (wrong resolution), but of the "block" character which gets displayed as quad characters - with too many of them displayed on screen than possible without reusing some of them.

As for Turtles, which has been mentioned - I don't think that one does any mid-screen changes. If you look at the screenshots closely, you'll realize it's all barely doable without rewrites. The 4 quad characters form the score display at the bottom. The four redefinable sprites show the player turtle (2 colors), the house (or the kid turtle climbing the player turtle, which disappears when the house appears) and either the bombs in the middle or the bomb you've layed (they flash in a way that they are actually shown alternatingly). The 12 allowed single characters display the 6 question marks and the 4 to 6 enemy bugs.

Tue Dec 26, 2006 10:40 pm


Rene_G7400

Joined: 06 Mar 2006
Posts: 651
Location: Netherlands
 
> Puzzle Piece Panic (if it has been released already?) - rewrites the sprites to display the puzzle

Would be a good test, but hasn't been released yet.

> Alien Invaders - Plus! - displays 3 rows of 8 aliens each, making for 24 sprites, so there must be some rewriting going on.

Those aliens are NOT sprites, there are no rewrites in this game.

> P.T.Barnum's Acrobats - displaying 3 rows of 8 balls each + some men

Like Alien Invaders - Plus, these are made with standard characters and quads, so no rewrites.

> As for Turtles, which has been mentioned - I don't think that one does any mid-screen changes.

Correct.

Tue Dec 26, 2006 11:35 pm       


Kurt_Woloch

Joined: 08 Jun 2006
Posts: 13
Location: Vienna

>> Alien Invaders - Plus! - displays 3 rows of 8 aliens each, making for 24 sprites, so there must be some rewriting going on.

>Those aliens are NOT sprites, there are no rewrites in this game.

OK, so I used the wrong term... I re-read the tech manual yesterday, and "sprites" on the G7000 only refer to the 4 redefineable ones. The other moving objects are called "single characters" and "quad characters".

So, let's take a closer look at this. If the upper two rows of aliens get displayed by quad characters, you need 8 single characters for the lower one, 2 for the digits on the left and right side, and 2 for your ship, which makes 12, leaving the 4 redefinable sprites which get used for the alien on top and your shot. So, you're right, it is doable without rewrites.


>> P.T.Barnum's Acrobats - displaying 3 rows of 8 balls each + some men

>Like Alien Invaders - Plus, these are made with standard characters and quads, so no rewrites.

OK, let's assume that the balloons get displayed by the single characters and quad characters. What occurs to me here is that the balloons are farther apart from each other than the digits of the score display at the bottom. I thought the vertical distance between the characters a quad character consists of is always the same? From the spacing given here, it doesn't seem that way, so how would you adjust the spacing of quad characters?

Other than that, you're right, it seems to be barely doable without rewrites. Obviously, the 2 men shown and the teeter-totter are displayed using the 4 redefinable sprites (1 for each man, 2 for the teeter-totter). If you use the 4 quad characters for the upper two rows of ballons, you need 8 single characters for the lowest row, and another 4 for the score display... which makes ecactly the 12 that are possible. So, everything's used up, and - no rewrites, IF there is a way to adjust the spacing of quad characters.

Wed Dec 27, 2006 3:57 pm           


Rene_G7400

Joined: 06 Mar 2006
Posts: 651
Location: Netherlands

   Kurt_Woloch wrote:
   
>> P.T.Barnum's Acrobats - displaying 3 rows of 8 balls each + some men

>Like Alien Invaders - Plus, these are made with standard characters and quads, so no rewrites.

OK, let's assume that the balloons get displayed by the single characters and quad characters. What occurs to me here is that the balloons are farther apart from each other than the digits of the score display at the bottom. I thought the vertical distance between the characters a quad character consists of is always the same? From the spacing given here, it doesn't seem that way, so how would you adjust the spacing of quad characters?

Other than that, you're right, it seems to be barely doable without rewrites. Obviously, the 2 men shown and the teeter-totter are displayed using the 4 redefinable sprites (1 for each man, 2 for the teeter-totter). If you use the 4 quad characters for the upper two rows of ballons, you need 8 single characters for the lowest row, and another 4 for the score display... which makes ecactly the 12 that are possible. So, everything's used up, and - no rewrites, IF there is a way to adjust the spacing of quad characters.


There is no way to adjust the spacing of characters inside a quad, but the quad's are definitely being used for the balloons. In a quad there is always a space between the characters. In most games two quad's are interleaved for the high-score display, so they fill up each other's spaces.

Wed Dec 27, 2006 6:39 pm       

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