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STUNT CAR RACER?


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#501 Gunstar OFFLINE  

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Posted Sun Mar 17, 2019 11:27 AM

It *almost* makes me want to trade my A8 for a BBC! Except for the God-awful colors (and 1001 other things the A8 does better)...I'll just have to "settle" for a Rapidus I guess...
 



#502 emkay OFFLINE  

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Posted Sun Mar 17, 2019 12:28 PM

highest fps by framecount
C64 6
Atari 9
BBC 12

#503 VincentGR OFFLINE  

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Posted Sun Mar 17, 2019 12:45 PM

Seems faster than the 16bit version to me.



#504 emkay OFFLINE  

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Posted Sun Mar 17, 2019 1:04 PM

Seems faster than the 16bit version to me.


Could belong to the "grid" graphics with low details. That was the cause why the C64 version looked playable once.

#505 VincentGR OFFLINE  

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Posted Sun Mar 17, 2019 1:21 PM

Could belong to the "grid" graphics with low details. That was the cause why the C64 version looked playable once.

 

Indeed with higher resolution but there is a 68000 behind :-/

Although I grew up with the Amiga version, this looks like the DOS one with unlocked framerate.



#506 emkay OFFLINE  

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Posted Mon Mar 25, 2019 10:05 AM

Interesting to see that the pure CPU speed is the relevant part to the shown fps.
Even by the "tricks" of using the character attributes for the sky, the C64 is exactly at half the speed of the BBC version.
The coder stated that the BBC has to handle everything bytewise in the graphics it offers.
So it seems, the character mode isn't really giving more speed. The benefit is the additional color of the sky.
The BBC Game Screen uses 4 colors.

#507 emkay OFFLINE  

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Posted Mon Mar 25, 2019 11:14 PM

Even more interesting. Now that the BBC version is rewritten to handle the game in linear graphics, how much would be needed to adopt that for the Atari. Particular for a turbo mode in Antic D ?
I wonder if the 12fps could be topped.

#508 _The Doctor__ OFFLINE  

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Posted Tue Mar 26, 2019 8:38 AM

eMkay, you do know a couple coders, and you have some ideas, maybe you could get together with all and make it happen. Just to show what can be done. Nothing says it better than to have it in front of the eyes.



#509 Irgendwer OFFLINE  

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Posted Tue Mar 26, 2019 4:02 PM

Now that the BBC version is rewritten to handle the game in linear graphics, how much would be needed to adopt that for the Atari.

 

Wrong, as usual:

https://www.dfstudio...screen-formats/



#510 emkay OFFLINE  

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Posted Wed Mar 27, 2019 12:10 AM

Wrong, as usual:
https://www.dfstudio...screen-formats/




Kieran Connell:

The BBC doesn't have a character attribute mode so the sky is filled by filling the screen pixels directly (so 8x bytes required per character.) Fortunately the BBC Micro has a faster 6502 CPU so we have enough time to do this (along with plotting the sprites in software and everything else that has to be done manually without the mighty VIC-II chip.) You can see the final results in the other video on my channel. More technical info on the Stardot forum and happy to answer questions at greater length there.

Edited by emkay, Wed Mar 27, 2019 12:13 AM.


#511 emkay OFFLINE  

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Posted Thu Mar 28, 2019 3:43 PM

No answer yet? OK, let's have a closer look there:

Even IF still the base of the code is handling character graphics, EVERY BENEFIT of character graphics is gone in the BBC version.
While the C64 is based on Character Graphics, supporting the faster drawing for the sky, on the BBC version now it is more a brake than an accelerator.
Stripping off the character handling would offer even more speed.
On the Atari the character mode steals a lot CPU cycles that would be better used for the 3d calculations.

#512 Irgendwer OFFLINE  

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Posted Fri Mar 29, 2019 9:26 AM

Even IF still the base of the code is handling character graphics, EVERY BENEFIT of character graphics is gone in the BBC version.

 

This has nothing to do (excluding the hardware simplicity aspects) with character graphics, it's just the way the screen memory is organized on the C64 and BBC: In character like cells.

Stating that "EVERY BENEFIT of character graphics is gone" shows again how less you know about programming. Even this "not natural" non linear screen memory organization can be used beneficial as it allows to control a quite compact local area of graphics.

 

Speaking 6502 here, to color the upper left cell area uniform you can do this (simplified) with:

       ldx #7
next:  sta screenmemory, x
       dex
       bpl next

While in a 40 byte linear screen memory scenario you leave the 8 bit offset after the 6th line (7*40 = 280 > 255), complicating the code and slowing it down.

I'm not saying that a cell based screen memory is better (often it's not), but if your code targets already the idea of such local cells (sky, ground) you can use that organization beneficial.

 

You would do yourself (and us) a favor, if you don't act like your statements reflect the absolute truth - they don't.


Edited by Irgendwer, Fri Mar 29, 2019 9:28 AM.


#513 Wrathchild OFFLINE  

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Posted Fri Mar 29, 2019 10:01 AM

To add to Irgendwer's points, the difference between the BBC and the C64 is that the C64 includes the colour-map support and hence it can 'paint' a large area of character cells very efficiently whereas the BBC would have to write to the screen memory (and so has only the 4 colours available). However, I would imagine that is balanced due to the BBC Master making use of the additional instructions it's processor offers as they would also give a speed improvement.


Edited by Wrathchild, Fri Mar 29, 2019 10:57 AM.


#514 emkay OFFLINE  

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Posted Fri Mar 29, 2019 11:56 AM

Sometimes I do not wonder why the Atari never gets the missing software.


What a loose sentence:

Stating that "EVERY BENEFIT of character graphics is gone" shows again how less you know about programming. Even this "not natural" non linear screen memory organization can be used beneficial as it allows to control a quite compact local area of graphics.

We're not talking about a gamescreen where the relevant parts could be repeated or mirrored.
If the coder decides to use "clusters" for better handling of ranges of the screen, he has to re-calculate the screen buffer for the other stuff that is needed to be calculated. The screen needs to be build for constantly changing the whole screen buffer, to get the calculation linear.
The real benefit in the C64 version is to get the screen color by just setting the color information into a block of 8 bytes. This refers to the lines that build the border between the Sky and the Ground. On the BBS the Engine still calculates the 8 byte character range and changes the lines afterwards to get the Sky distinguished from the ground.
Comparing the C64 game to the CPC or Spectrum version, there is a clear indicator that the character mode doesn't speed up the game at 1st.

Edited by emkay, Fri Mar 29, 2019 12:10 PM.





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