Just so we're clear. Upscaling is done after output. So if the game outputs at 480, it is upscaled if each pixel is stretched to give a 1080 display. Each pixel is essentially streched by a factor of 2.25.

Any one who knows how 3D graphics works, knows that geometry is computed by the engine, thus its not scaled in away regardless of the resolution that it is rendered. Only textures and other 2d images would be scalled and those can be left unchanged, so the effect is 480p textures on 3d models output to 1080.

So it is definetively native.

Native just means that its display resolution = output resolution. When Scaled display resolution != output resolution, i.e. upscalling display resolution > output resolution, thus stretching. Downscalling display resolution < ouput resolution, thus compression.

So is it a change in resolution like what you can do for old pc games?

Guys, native 1080p has absolutely nothing to do with the assets/textures.  It's all in how the lines between vertices are rendered.  Nothing more.  Emulators have had the ability to render games in whatever native resolution your monitor and CPU/GPU could handle for a while now.  I've been playing 1080p PS1 games for years. The assets are the same old ones from 15-20 years ago, but the game is in full blown 1080p (full screen, obviously, and it was actually 1200p when I had my old CRT). Same thing with PS2 games and Wii games in recent years as emulators and processing power have caught up.

In fact they can be rendered in 1080p.
To simplify, upscaling is about rendering at a given resolution which give you a picture, say a 320x200 for PS1, then make every pixel bigger to fit an higher resolution. A simple upscaler just make pixel bigger. A good upscaling will not just make pixel bigger, but filter pixels to render sub pixel in a less visible way. It will produce a very mixed result.

An other way through emulation is to render directly the 3D at the target result. To say it very simply, if you have a line going from A to B, instead of making rendering it in a 320x200 matrix, you render in a 1080p matrix. You can add filter for textures to improve the rendering, and even tweaks some know effects. For example most of the game will render a semi transparent window using the same primitives, so you can render it with a beautifull modern gpu accelerated transparency. There is about no limit on how you could enhance the graphics, like replacing 8 bits low res textures with high res procedural textures, adding shaders depending of the game type.

So, that's really a native 1080p. The only problem is that the game is not made for that, so you can have a lot of code that produce glitches, etc., you have lot of game to test and simply can't achieve a 100% compatibilty.

Anyway, here are the pics from epsxe, the ps1/2 PC emulator that render this way. You can see the limitations, the background is a picture in 2d so you can't do better rendering, just add a blurry upscale.

You can watch shaders experimentation on youtube (switch to 720p or 1080p) : http://www.youtube.com/watch?v=2CWmrMyOl9o

This is exactly what I was thinking the game is cleaner but the textures are still blurry and polygons are more pronounced and blocky. I was always of the view that native 1080p meant cleaner textures (or more detailed textures if you like).

I understand you explanation and it is just as I thought, the game basically looks the same just cleaner. I also play on pc I just don't bother normally to discuss graphics.

My thing is all the PR behind native 1080p, if you can just take a game made 15 years ago and make it native 1080p, then for me it holds no weight in bringing it up in a graphics discussion now.

Really, strictly speaking native 1080p is about having a 1080p rendering, which is the case in such an emulation. The massive aliasing (on my screen I can see a pixel is more than 1 millimeter) is no more, you have clean (but blocky) rendering for lines.

Anyway, it's not and will never be the same than current gen 1080p rendering with high detailed textures, high polygon count, shaders, particules that shines within a high definition rendering. In fact as you said, it even create new problems, the low polygon count hidden by big pixels become a lot more visible. Some of the problems can be improved to some point, with better texture filtering. Also an other problem for PS1 is the high unstability of 3D (low accuracy I assume) that was already here in low def, but become even more painfull. But what I've shown is on of the worst case with 2d background, on PS1. A full 3D game from PS2 would render a lot better. And I really think in any case it renders a lot better than a television upscalem which is actually the point.