New 3d Perspective Shader

It's not finished, optimized or ported to DX11 yet, but just thought I'd show off my progress so far, since I know a few people have been waiting for a shader like this, and there are some others who like tinkering with shaders...

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Not sure why there are visual artifacts at the edges...

Cheers!
The code needs commenting, and variable names need changing to something more descriptive, so those people interested in how it works can understand what's going on (it's actually pretty simple, believe it or not).
There's room for optimization - doing the 3D rotations by matrix multiplication, for example.
I'll probably add a "zoom(-out)" parameter, so you don't need to add an empty border around the image.
I'd like to fix those visual artifacts at the edges somehow...
I'm not promising anything, but there's also the potential for lighting effects (Phong shading, specular maps...).

I definitely won't be porting to Android/iOS, as I don't have any means of testing on those runtimes. I should be able to do a DX11 port, but I might not get around to it for a while... So yeah, go ahead if you want to - or maybe wait until there's a more "final" version.
As always, anyone is free to modify, share and use the shader in any way they like.

EDIT: If you set the border to transparent instead of white, those visual artifacts go away

I've changed it now, but the original picture of the dog had a white border. That was necessary because otherwise as the image rotates, it no longer fits the object and bits get cut off (hence the idea of a zoom-out parameter). I thought that since the background of the frame was white, you wouldn't be able to see the border, but for some reason there are those ugly visual artifacts at the edges. But if you use a border of transparent pixels instead of white, those disappear.

I can't quite tell if this example:
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...is using per-pixel lighting or not?
You might be able to get that effect by just having a "highlight" layer overlaying the card, and varying its opacity according to the angle of the card. That would be more efficient that doing it in the shader anyway, since it's then one calculation per object, not one per pixel.

That was quick! Nice work

I've noticed (and should have anticipated) that the shader only works perfectly with square textures, so if your object is not square, you should add transparent margins to make it square. I have a feeling this would be tough to fix.

Flat shading is not too complicated, but I'm still not sure if it's a good idea to put it in the shader. As mentioned earlier, it's probably better to do the calculations once using CF2.5 events, rather than repeating them for each of the texture's thousands of pixels in the shader. Per pixel shading probably isn't worth it anyway, since we're only talking about simple flat surfaces without shadows, multiple light sources, etc.

Sorry NaitorStudios, you're going to hate me, but I've updated the shader...

Download: Please login to see this link. (version 1.1)

Changes:
+ Commented all shader code (in case anyone's interested).
+ Should now work properly with non-square textures.
+ Added adjustable ambient lighting and a single configurable directional light source.

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Quote from NaitorStudios

Here's the DX11 Port
Also fixed the light intensity that wasn't connected to anything...

Oh, I just forgot to remove the light intensity parameter from the xml - I was testing it with that first, before swapping to a float4 colour instead. There's no reason to have both, since a lighter colour is the same as a more intense light anyway (unless you want super intense lights, I suppose).
Cheers though

Quote from aenever

Just wondering like a playing card, is there a way to have two different sides to a rotating card (front and back)?

I've modified the shader to add an image parameter for the reverse side of the object. Lighting still only works correctly for the front side (this is proving hard to fix), so if you're using both sides, you will need to disable it by setting the ambient light to pure white, and the directional light to pure black.

Download: Please login to see this link. (version 1.2)

I do believe I've finally cracked the lighting problem!

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Just need to fix up the code a bit (it's full of hacks and the remnants of failed attempts right now lol), and then I should be able to provide a link to the file soon...