Jump to content
rpc_games

CENTRON 3D - Title Screen Shot

Recommended Posts

Good one, Bryan - I missed that.

 

So it's looking like fullscreen swapping palettes and image data - 1st screen with colour base then 2nd with luma.

For a capture card with the correct settings or frame-blended emulation, or possibly LCD TV it'd work.

 

Real hardware on CRT, not quite the case - big time flicker.

 

Also I'd say fairly sure the video isn't from emulation - go fullscreen and you can see the usual colour error at pixel edges and the vertical cycle noise on the Gr. 0 screen.

 

I guess in this day & age where practically all have access to capture device or LCD TV, it's a valid technique to get more colour going on.

In fact capture devices and LCD TVs will often give you real interlace (480i) for free as it's a side-effect of how they process the non-standard progressive image that most old computers generate.

Share this post


Link to post
Share on other sites

hmmm that's a pity...

 

But still... I was really under the impression that rpc_games was or is not aware of anything that went on the last 20 years in the atari 8bit scene. So let's assume that he has invented this from scratch, it is still a nice achievement. Although it is not new, and not exact what I'm waiting for (I'm with CRT televisions/screens since those give the very best result IMHO) I still think: ok... continue, show us more.

  • Like 1

Share this post


Link to post
Share on other sites

Screen shot flickery or not is ok but lets see something in game even if its only at alpha stage?

 

Whet our appetite :)

  • Like 1

Share this post


Link to post
Share on other sites

If it flickers it would be a pity.

Of course oyu can say that it looks amazing on (filtering) LCD display and so on. But then I could as easily install a VBXE and have an even higher resolution.

It would be great if this "CMODE" doesn't even exist. Look, how "we" had fun discussing this "new mode" and some even analyze a Youtube video. :)

 

And I am still hoping that there might be a new mode (without flicker). Although in the times when some guys even decap and analyze the chips I don't think there will be such surprises as in the 80s/90s with APAC, HIP and so on.

  • Like 1

Share this post


Link to post
Share on other sites

@ everyone: hehehe You guys are unbelievable !! Flicker on not flicker, that is the question :) hehehe

 

The answer is....... Ready for it...... You'll just have to wait for the game demo....... It's coming.

 

Now where's the on button :) hehehehe ahh here it is... Commodore 64 Basic..... WHAT THE !!!

 

hehehe :)

 

Pete

  • Like 1

Share this post


Link to post
Share on other sites

Something else: The shading appears to be 8 luma, not 16. I noticed also, that the color seems to blend onto the next scanline, just look below the letters. So I am wondering if we're dealing with a straight graphics 10 screen and color palette changes. Altho changing 9 color palettes either on scanlines or in VBI would be time intensive, I've done it (at least full frame) in my Super10+ ICE mode. So we're talking 72 colors onscreen here in this case.

 

Would still require some flicker but maybe could be staggered by alternating the color settings in each frame.

 

704 remains constant as the BG color in both frames. This leaves eight reigsters to stagger as follows:

instance one: Make 705, 707, 709, 711 equal to luma 2,6, 10, and 14 respectively, even numbered registers will be colors

instance two: Make 706, 708, 710, and 712 equal to luma 4, 8, 12, and 0, while the odd numbered ones are the other colors.

 

Maybe staggering the color registers like this would reduce flicker?

 

Using LMS to repeat a scanline, make these color changes on each scanline,then use a display list jitter to shift the screen up and down by about 2 scanlines. It's still flickering, but the result is a heck of a lot easier on the eyes than full frame flicker and would definitely be playable even in PAL. Maybe with the lower screen resolution, you'd have more CPU time to make 9 color changes each line?

Share this post


Link to post
Share on other sites

Capture will usually assume interlace so give blended scanlines rather than the normal every 2nd line blank.

 

It's GTIA paletted mode for sure, the pixel offset is the giveaway. Doing 8 colour changes in VBI is nothing special - even doing something like that every 4th scanline isn't a big slowdown although of course there's insufficient cycles to do so cleanly in a DLI situation.

Share this post


Link to post
Share on other sites

I'm also sure that the color frame is being shifted down by 4 scanlines each frame, maybe using a trick on the skip scanlines DL instructions. The color line underneath the letters sort of shows this.

Share this post


Link to post
Share on other sites

Well even before RPC games released anything from their brandnew 3D game, RPC games got already a lot of feedback... it's so much (positive, negative, detailed, cynical, enthusiasm etc. etc) I'd rather call that 360-degrees feedback..... or.... yes... 3D-Feedback :D

 

Eventually this turns out to be an interesting thread.

  • Like 1

Share this post


Link to post
Share on other sites

I don't think there's any downward shift - PAL blending is only useful between adjacent scanlines and you can use a 1 pixel jitter between frames to make it look more filled-in. Shifting down by 4 wouldn't do anything useful.

 

I stand by the frame-blending theory. Almost tempted to hook a machine up to my LCD TV and try some out.

 

It'd make more sense to use DLI + VScrol trick rather than repeated LMS to get the 4x4 pixels. The LMS method costs 43 extra cycles per the 3 extra scanlines, doing DLIs costs much less.

On something like a title screen though it doesn't really matter.

Edited by Rybags

Share this post


Link to post
Share on other sites

arent the RPC guys from Australia which means PAL territory? so not sure if this mode looks good on NTSC.

Share this post


Link to post
Share on other sites

I don't think PAL colour blending has anything to do with it - frame blending being my theory so LCD TV or capture device being needed with the TV standard not mattering.

Edited by Rybags

Share this post


Link to post
Share on other sites

e.g. Space Harrier XE good in PAL AND NTSC or only in PAL?

 

Better in NTSC, because the flicker is faster/less noticeable.

Share this post


Link to post
Share on other sites

I've done a quick/dirty Basic program with VBI that can be used to show the effect.

 

FBTEST1.BAS

 

post-7804-0-98486800-1401366975_thumb.jpg post-7804-0-75830100-1401367114_thumb.jpg

 

Left is a photo of my 32 inch LCD TV from 130XE Composite video, right is Altirra screenshot with frame blending enabled.

 

The LCD isn't quite as I expected - I thought the saturation wouldn't have suffered so much although I've got the colour control on the TV set fairly low. Frame blending is definately going on here as there is no flicker at all. The same thing on a CRT looks an absolute mess.

 

Also, the colour bars themselves would probably look better if done solid or at least with black inbetween. But the program is there, so can be played around with.

The DATA lines 100,110 hold the palettes for each frame - line 115 has the colour data with luma 2, change which of 110 or 115 is a REM to select alternate colour set.

 

 

It does illustrate though that this technique can be done cheaply in CPU terms - there's only a VBI going on, no DLIs at all, a few dozen cycles burnt per frame.

If the 80 x 48 mode is desired, then it could be done with memory savings and not much extra cost in CPU terms.

Edited by Rybags
  • Like 1

Share this post


Link to post
Share on other sites

Nice one Rybags, frame blending a MUST on this.....Well without it I could not really bare to watch it long.

Share this post


Link to post
Share on other sites

The thing about this "mode" - I see no reason why alternating Gr. 9 and Gr. 11 screens shouldn't be used instead.

 

Using a pair of Gr. 10 screens, you only have 72 useful colour combinations (you need background black on both screens so lose some combos there).

 

Using the Gr. 9 / 11 you should get 256 colours since all the lumas are available. Although PMG usage in Gr. 10 is less restricted (but with disadvantage that their colours are shared with parts of the playfield)

Share this post


Link to post
Share on other sites

I've had an idea for a while to make a program that puts 2 flickering colors on one half of the screen and 2 different ones on the other half. You would then select which one flickers less. It would go through all the combinations until it had generated a table of color combinations from best to worst. Then, you could select 2 palettes which would give you the best tradeoff between available color combinations and flicker.

 

-Bry

  • Like 1

Share this post


Link to post
Share on other sites

This works on LCD thanks to the way they handle interlaced analog signals. The frame consists of both fields at once which is why there's no flicker.

 

It's probably more a trick of the eye than anything that you percieve the blended fields as colours of varying luminence.

 

I think it's probably worthwhile with experimentation - it might be the case that brighter colours would look better if the colour component was at a brighter value.

 

e.g. have the colour field as black + 3 sets of colours at luma 2 and luma 8, then a 4th colour at luma 2 (9 palette entries).

Pair the darker colours with luma values 0 thru 6, use the brighter colours paired with lumas 8 thru 14.

  • Like 1

Share this post


Link to post
Share on other sites

Well the advantage in double-10, is that if you do no color palette changes (as opposed to 9 changes every scanline) you can checkerboard the colors to get less flicker if you did no color changes. Though you'd only get 45 colors, but it really produces a nice effect.

 

Good example is in this post:

 

http://atariage.com/forums/topic/188370-doing-pictures-using-super-irg-2-and-other-ice-modes/?p=2555685

Share this post


Link to post
Share on other sites

Frame-blending = no flicker anyway. It's due to how the LCD TV operates. And there's no tedious checkerboard or interleaving needed.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...