Perspective correct texturing on DS?

[Squeak]

What kind of texturing method does the DS use?
Sometimes at low angles and up close, there is a tiny bit of warping, like PSone games used to do, but apart from those rare instances, it seems that the DS has perspective correct texturing.
So does Nintendo waste tonnes of polygons to get perspective correction, or is it some kind of clever hack?

 

[Branduil]

I don't know what the DS uses, it seems to have a very small amount of warping, it's really only noticeable when you look for it. It's certainly better than the PS1's eyesight-murdering texturing.

 

[see colon]

it's pretty software dependant, also. some games (asphalt urban GT) have plenty of warping, while others (mario kart) have little to none.

 

[Karamazov]

it's pretty software dependant, also. some games (asphalt urban GT) have plenty of warping, while others (mario kart) have little to none.

That may be because asphalt urban GT is a port of the NGAGE version.

 

[Blade]

I think it's wise to take Mario Kart as a prime example of a DS' graphical abilities.

If a developer can't make their game look as good as MKDS and run at MKDS's 60fps.. then they're not trying hard enough.

 

[swaaye]

In the games I've played on it, it looked at least as good as N64. Which I always thought was pretty much perfect.

 

[Corwin_B]

Lost in Blue has some warping in some environments (not all).

 

[Iron Tiger]

I've noticed even some Dreamcast games have texture warping, so I don't think that having hardware support for perspective correction necessarily means you'll have perfectly aligned textures every time.

 

[Fox5]

I've noticed even some Dreamcast games have texture warping, so I don't think that having hardware support for perspective correction necessarily means you'll have perfectly aligned textures every time.

Were those dreamcast games PSX ports? Dreamcast got quite a few of those.

 

[see colon]

i've seen early ps2 games with perspective correction issues. the first nascar game (nascar thunder 2001?) released on the system is one i definatly remember, because i saw it in an in store demo right next to the dreamcast playing tokyo extreame racer, and the DC game looked signifigantly nicer to me.

 

[Toasty]

I've never actually seen a DS in action but I have a degree of experience with 3D on embedded devices.

If you're doing a divide per pixel you shouldn't be able to see warping for any situation. It may be that the DS hardware does a divide for every 8 or 16 pixels (saving you from needing a pipelined divider) and interpolates linearly between. I've found that this technique is barely noticeable if you use it only across scanlines, so either just the x or just the y direction (Pixomatic comes to mind as a good example). However, if it's done with 8x8 or 16x16 blocks in both the x and y direction then it can be spotted but the effect is still quite minimal for most circumstances.

 

[akira888]

If I remember correctly Carmack and Abrash did something almost exactly like this in the software renderer for Quake 1. Perspective correct texture coordinates were generated every eight pixels (in both x and y) and were bilinearly interpolated within the 8x8 pixel blocks.

 

[Iron Tiger]

Were those dreamcast games PSX ports? Dreamcast got quite a few of those.

Not any that come to mind. The Sonic Adventure games had some texture curling along the edges of the screen and they definitely weren't PS1 ports.

 

[Simon F]

Not any that come to mind. The Sonic Adventure games had some texture curling along the edges of the screen and they definitely weren't PS1 ports.

The DC hardware did per-pixel perspective correct texturing so, provided you weren't imagining it or had a tv (e.g. wide screen?) that did something funny with scanning (e.g. stretching the edges with 4:3 images), then the game must have been doing something "wacky".

 

[Fox5]

The DC hardware did per-pixel perspective correct texturing so, provided you weren't imagining it or had a tv (e.g. wide screen?) that did something funny with scanning (e.g. stretching the edges with 4:3 images), then the game must have been doing something "wacky".

I've noticed in emulation of many n64 games there's typically a distorted border around the images that would be cut off by overscan on a normal tv. Typically the border is a continuation of the game's graphics but stretched.

 

[Iron Tiger]

The DC hardware did per-pixel perspective correct texturing so, provided you weren't imagining it or had a tv (e.g. wide screen?) that did something funny with scanning (e.g. stretching the edges with 4:3 images), then the game must have been doing something "wacky".

I actually noticed it in printed screenshots before I ever got a DC to confirm it. It wasn't nearly as ugly or pervasive as on a PS1.

EDIT: This review of Spirit of Speed 1937 makes specific mention of texture warping (though it's not apparent in the few screenshots accompanying).

This review of Dino Crisis also mentions it, and it's visible in the yellow and black caution markings in this and other screens.

There are more mentions of the artifact in reviews of other DC games, but it's a lot harder to find pics of it.

 

[DeanoC]

The most probably reason you've seen warping on DC is that the developers choose (or didn't understand the maths) not to set the W component correctly.

All perspective interpolation can be made linear if you want... why you would? Err quick port of a PS1 title is the obvious one...

Given the DC had software TnL its entirely possible (nay likely) that some games just ported the PS1 geometry engine, including subdivision and not passing the Z/W through.

 

[Simon F]

its entirely possible (nay likely) that some games just ported the PS1 geometry engine, .

I think I've seen something similar with a port to MBX.... even when it has HW T&L

 

[see colon]

This review of Dino Crisis also mentions it, and it's visible in the yellow and black caution markings in this and other screens.

There are more mentions of the artifact in reviews of other DC games, but it's a lot harder to find pics of it.

isn't the yellow caution marker part of the pre-rendered background? i never played dino crisis on the DC, but i did play RE3, and there wasn't even texture filtering on the characters.

 

[Fox5]

I actually noticed it in printed screenshots before I ever got a DC to confirm it. It wasn't nearly as ugly or pervasive as on a PS1.

EDIT: This review of Spirit of Speed 1937 makes specific mention of texture warping (though it's not apparent in the few screenshots accompanying).

This review of Dino Crisis also mentions it, and it's visible in the yellow and black caution markings in this and other screens.

There are more mentions of the artifact in reviews of other DC games, but it's a lot harder to find pics of it.

Dino Crisis is a PsOne game so that probably explains it. I still say if there was warping on the edges of the screen, it was likely stuff that was cut off by overscan anyway and didn't matter. Not to mention that Dino Crisis used prerendered backgrounds.
Spirit of Speed is likely a port from somewhere too, perhaps a software rendered pc game.