So, like, is Star Blade does use teh FMV for its polygons or not, yo?

[Barone]

So I had the idea to take a deeper look into Silpheed and Starblade.
I used the Gens/GS emulator, with the "Double" option for video activated (just to make the images more "visible") and no extra filtering (fast blur disabled).
I played with the VDP layers a bit and also with the debugger.
**Debugger info do NOT depends on which layers I made visible.

Here we go (feel free to move these last posts if 'cause maybe it's going a bit off topic now...):

Silpheed

Intro
-Game screenshot 1: Everything is on the layer "Scroll B"


-VDP Debug for screenshot 1: Remember to compare the memory content with the Starblade ones.


-Sega CD GFX Debug for screenshot 1: looks like everything is here.


-Game screenshot 2: Still everything on layer the "Scroll B"


-VDP Debug for screenshot 2: Nothing here.



Gameplay
-Game screenshot 3


-VDP Debug for screenshot 3: Just some sprites here.


-Sega CD GFX Debug for screenshot 3: looks like our Earth is here.


-Game screenshot 4: just some layer analysis.


-Game screenshot 5: just some layer analysis.


-Game screenshot 6


-VDP Debug for screenshot 6


-Sega CD GFX Debug for screenshot 6


-Game screenshot 7


-Sega CD GFX Debug for screenshot 7: yep, the FMV background is always here.


-Game screenshot 8: Just more layer analysis.


-Game screenshot 9: Just more layer analysis.


-Game screenshot 10: Just more layer analysis.

[Barone]

Starblade

First Segment
-Game screenshot 1


-VDP Debug for screenshot 1: Remember to compare the memory content with the Silpheed ones.


-Sega CD GFX Debug for screenshot 1: hummm...


-Game screenshot 2: Some layer analysis.


-Game screenshot 3: Some layer analysis.


-Game screenshot 4


-VDP Debug for screenshot 4


-Sega CD GFX Debug for screenshot 4


-Game screenshot 5: Some layer analysis.


-Game screenshot 6


-VDP Debug for screenshot 6


-Sega CD GFX Debug for screenshot 6



Second Segment
-Game screenshot 7


-VDP Debug for screenshot 7: Bingo!


-Sega CD GFX Debug for screenshot 7


-Game screenshot 8


-VDP Debug for screenshot 8



What do you think now, Joe?
Chilly Willy?
sheath?

[sheath]

What exactly do you mean by "stream actual game data from the disk on the fly"? How is "streaming" game data different from accessing/loading it? Soul Reaver eliminated the appearance of load times by having choke points in the environment. Similar to portal rendering.

I mean eliminating static screen load times and loading new level segments. Sonic CD has the time warp scenes to load the new level data, if they had achieved the instantaneous time warp that the designer wanted it would be what I am referring to. I suppose Soul Star loads new graphics in quick transitional screens though. I don't even know how much RAM a fully polygonal Sega CD game would need without loading, some folks insist that Stellar Fire is fully polygonal, and the level of detail isn't all that high, it's low enough that they could all be pre-rendered sprites with turning animations.

For StarBlade to be rendering on the fly it would also have to be streaming new data into RAM to render the next sequence without any pausing. Whereas streaming video can stream individual frames from the disk and keep up, or entire files if they are small enough, filling the screen with polygons and changing scenes as often as StarBlade does would be a lot different. About the only thing I could do is take an example of how much one polygon weighs in RAM and figure out how many polygons would fill up 512KB + 256KB. I used to have the "standard" weight in bytes of a polygon ... wait I found it.

So let's assume that a polygon is 32-40 bytes in RAM, I'll stick to the high end. 768 KBs is 786,432 Bytes divided by 32 that's 24,576 polygons. Divided by 40 it's 19,661 polygons. That is just how many polygons can be loaded into all of the Sega CD's RAM, I haven't seen any guesstimates about how many polygons per second the Sega CD's Sub CPU plus Graphics Co-Processor would be capable of. I also don't know if such a rendering engine would need to be limited to the 512KB, if so that would be 16,384-13,107 polygons.

I seem to remember SNES SFX games being in the range of 5-7k polygons per second, and VR SVP being around 10k pps, which is also around what early 3DO and Jaguar games were boasting. I'm also not sure, if 32-40 bytes per polygon is standard, how 32X games could have achieved 25k polys in game with only dual 256KB frame buffers to work with.

[sheath]

What exactly do you mean by "stream actual game data from the disk on the fly"? How is "streaming" game data different from accessing/loading it? Soul Reaver eliminated the appearance of load times by having choke points in the environment. Similar to portal rendering.

Googly moogly, I had a long reply and it got moderated. I'm talking about loading additional game data without using a static screen. I think Soul Star somewhat does it between level segments, and Sonic CD's time travel sequences is close but not the same. The designer of Sonic CD wanted it to be instantaneous or virtually so but they couldn't get the level data to load fast enough.

On the Sega CD's polygon capabilities, from what I can find online a four point polygon takes up anywhere between 32-40 bytes. Dividing the Sega CD's 768KB of RAM by 32-40 bytes makes something between 24,576-19,661 polygons. If for some reason the rendering engine would be limited to the Sega CD's 512 KB that would add up to 16,384-13,107 polygons. If I recall SNES SFX games were between 5-7,000 polygons per second, and Virtua Racing SVP boasted around 10,000, which is also around what early 3DO and Jaguar games were claiming.

I'd be shocked if the Sega CD could achieve those half again to nearly double the numbers with only the Sub CPU and Graphics CoProcessor. I guess it isn't too far fetched though. I have never seen a method for calculating what a processor could generate polygon wise, I'd love to know how though.

I don't know how, if 32-40 bytes per polygon is standard, the 32X could have achieved 25k polygons per second in game with only two 256KB frame buffers.-

-edit-

Great screenshots agostinho, at a glance it looks as though StarBlade isn't even using Sega CD Word RAM, instead it left the last thing loaded there during the Sega CD bios screen. That is, unless they're some how ingeniously using those the Sega and Sega CD logo tiles to generate polygons. The VDP pattern layers in StarBlade don't include the necessary colors for the polygonal objects, the blue for the ships and brown for the asteroids doesn't show up anywhere.

The Silpheed shots show gameplay relevant tiles in Word RAM, which is interesting because I wouldn't assume that FMV would show up as tiles in the Sega CD RAM, just as it was output from the Sega CD to the Genesis VDP. I wonder what other FMV games look like, I'm going to check out Stellar Fire now.

[Barone]

Great screenshots agostinho,

Thanks.

at a glance it looks as though StarBlade isn't even using Sega CD Word RAM

No, it just means that it isn't used for graphics.

The Silpheed shots show gameplay relevant tiles in Word RAM, which is interesting because I wouldn't assume that FMV would show up as tiles in the Sega CD RAM, just as it was output from the Sega CD to the Genesis VDP. I wonder what other FMV games look like, I'm going to check out Stellar Fire now.

OK, some other examples for comparison:

AH3 Thunderstrike:




BC Racers:




Dracula Unleashed:




Dragon's Lair:




F-15 Strike Eagle II:



F-22 Interceptor:



Loadstar:





Whatever Starblade is using, it doesn't seem to be FMV. IMO it is very close to what you see for those two 3D Genesis games.

[sheath]

The Thunderstrike shot is what I would expect to see in Sega CD Word RAM if the Sub CPU and Graphics CoProcessor were working on polygons. Either that or the shots that have the Sega CD RAM filled with junk not related to tiles. Those Genesis games do make it clear that the tiles don't necessarily have to be the right color to be what is displayed on screen though, I forgot about that.

-edit-

I can't seem to get Gens/GS or Gens Kmod to detect my Optical drive in Windows 7 64-bit, so I won't be contributing with Stellar Fire any time soon. ForceASPI doesn't work in Windows 7, and my drive is an HD-DVD/Bluray/DVD-R combo drive. I'm pretty sure I had it working in PSX and Saturn emulators though.

[Barone]

Yep, Starblade seems to be using something different than what we were expecting at first...

Hopefully Tom or Chilly will have a hint for us.

[sheath]

The Loadstar shot having the Sega CD Bios in word RAM and a bunch of tiles for the overlay in the VDP looks pretty similar to StarBlade's shots.

[Barone]

Hummm, I don't know sheath... The VDP debug for Starblade doesn't show overlay tiles (I think the hud is just drawn there) but several pieces that looks like the objects that you see on the screen. And Loadstar FMV is nowhere...
The word RAM part is similar though...

IMO the most important part is to notice that the objects don't seem to be in 3D on the VDP Debug for the Starblade, so it's not a FMV of pre-rendered 3D stuff. It's being rendered on the fly, using pre-calculated geometry or not.

[sheath]

Hummm, I don't know sheath... The VDP debug for Starblade doesn't show overlay tiles (I think the hud is just drawn there) but several pieces that looks like the objects that you see on the screen. And Loadstar FMV is nowhere...
The word RAM part is similar though...

IMO the most important part is to notice that the objects don't seem to be in 3D on the VDP Debug for the Starblade, so it's not a FMV of pre-rendered 3D stuff. It's being rendered on the fly, using pre-calculated geometry or not.

That's what I mean, in Loadstar the Hud is loaded in VDP memory as tiles, in StarBlade the VDP is filled with background elements behind the polygonal stuff and some miscellaneous tiles I can only suppose have to do with something that wasn't presently on screen. Apparently streaming FMV doesn't need to be loaded into the VDP like tiles, but it can be as was the case with Dragon's Layer. Dragon's Layer is just the animated objects and a static background though.

[TmEE]

You can scroll around in VDP VRAM by using some button, but I have long forgotten which. The screenshots only show below quarter of the VRAM.

[Barone]

That's what I mean, in Loadstar the Hud is loaded in VDP memory as tiles, in StarBlade the VDP is filled with background elements behind the polygonal stuff and some miscellaneous tiles I can only suppose have to do with something that wasn't presently on screen. Apparently streaming FMV doesn't need to be loaded into the VDP like tiles, but it can be as was the case with Dragon's Layer. Dragon's Layer is just the animated objects and a static background though.

I still think that you're missing some points... All things that you call background, like those blue big ships at the beginning, is always moving each face of the polygon like a poor render would do... If it was pre-rendered stuff, like Silpheed, it would not be like that. Compare to the 32-bit versions that do use FMV, the background does not have any of those "perspective" errors.

[sheath]

You can scroll around in VDP VRAM by using some button, but I have long forgotten which. The screenshots only show below quarter of the VRAM.

I was going to ask about that, I remember there being many pages for cart games. Dangit if I could just get my optical drive to work with Gens GS in W7.

Agostinho, for the StarBlade shots I was referring to the non-polygonal background, like the planet in the first shot, its graphics seem to be in the VDP shot like the planet in Silpheed was. Can you scroll through more of the VDP memory and find tiles for the polygonal ships (wire frame and filled)?

-edit-

Okay, I got Gens Kmod running on my XP laptop along with Gens GS. I only found a way to scroll in Vram in Kmod. Starblade does indeed have everything on screen in VDP RAM in tile format. Below is a VDP RAM dump of the scene with both of the polygonal ships and the planet from the very first scene. In the VDP the tiles related to the polygonal ships are changing on the fly.



Sega CD Word RAM dump of the same scene:


I don't know what that means in regard to whether the scenes are rendered in real time or streaming FMV. I had understood previously that the Sega CD's Graphics CoProcessor has a built in function to convert bitmaps to tiles, and the VDP can only display tile data.

[Barone]

VDP:

WORD RAM:



VDP:

WORD RAM:




VDP:

WORD RAM:




Thanks a lot TmEE, but I had to use GensKmod for the RAM images.

[sheath]

I just checked Stellar Fire and it looks identical to all of these. Word RAM is the Sega CD bios logos that changes palettes with what is on screen, VDP tiles display everything on screen at all times (which is what should be happening since it displays everything). These aren't really helping me decide whether anything, even the wireframe graphics in StarBlade, are rendered in real time by the Sega CD.

-edit-

To further muddy the water, I just watched my old 3DO StarBlade video, and some of the capital ships have destructable areas that leave huge craters in the ships when you shoot them. How were those done with FMV?