Smooth 2.5D Area Light Shadows

[Oogst]

Question: Does something like this already exists?

I have come up with a new technique to render area light shadows: Smooth 2.5D Area Light Shadows. I am wondering whether what I came up with is really new, so I hope you guys can tell me whether something similar already exists. Here's a video of what I implemented so far:

[youtube]F_MeY5iBnLc[/youtube]

I have built a little prototype of my technique, but it is far from finished yet. Let me first explain what area light shadows are, since I guess not everyone knows that:



Area light shadows are currently never used in games, because techniques to render them are incredibly slow, so they don't really work for real-time graphics.

The technique I came up with, is not a general solution: it only works for games that are viewed from the top, like Diablo and Torchlight. That is why I call it Smooth 2.5D Area Light Shadows. It is, however, very fast to render, so I think this technique would really be a big addition to these kinds of games.

Here are some results of my work:



The most important thing that is missing right now is working correctly with height. I have a simple solution for that, but I have not implemented that yet. This image shows what I mean:



So, how does my technique actually work? The basic idea is to render shadows to a render-texture from a top-down perspective. So the shadows are kind of similar to a height map:



This means that the main downside of my technique is that there cannot be several layers of shadow above each other:



I hope this explanation of how this technique works is clear enough. Feel free to ask any questions, and obviously I am looking forward to suggestions for improvements!

Anyway, right now my main question is whether this really is something new. Because if it is, then I am going to put a lot of work into the prototype and hope to present it at GDC Europe, so it would be great to know about that beforehand.

[aguru]

Interesting. But what about more complex shapes, e.g. a pyramid?

[CoreDumped]

Nice. How far do these shadows go? What happens when they hit a wall?

[Oogst]

Interesting. But what about more complex shapes, e.g. a pyramid?

Right now I only support vertical planes, but I intend to support freely rotated boxes and cylinders. If the pyramid is on the ground, then the top half of a diagonal box would represent that well enough.

Nice. How far do these shadows go? What happens when they hit a wall?

Shadow receivers can be any shape, so walls are totally okay, as are animated characters. I have not implemented height yet, though, so in the current version the shadow would go up the wall infinitely and not stop at the correct height.

[tuan kuranes]

Nearest technique I know of (seen in terrain renderer):
-> Render terrain + Object casting shadow from above as a heightmap (using a RTT)
-> using resulting RTT heightmap in order to do some "heightfield self shadowing" (=> see below for a list)
-> then render terrain + object using resulting shadow map

heightfield self shadowing techniques:

• Fast Global Illumination on Dynamic Height Fields
• Scalable Height Field Self-Shadowing (previous version of the above)
• Fast Soft Shadows on Height Fields via Multi-Resolution Image Processing
• Fast Height-Field Rendering under Image-Based Lighting(not freely available)

[hronet]

Looks somewhat related to Eric Haines shadows using plateaus as well

http://erich.realtimerendering.com/plateaus.pdf

[Sgw32]

Do you plan to release your leghting in to public?

[Oogst]

Looks somewhat related to Eric Haines shadows using plateaus as well

http://erich.realtimerendering.com/plateaus.pdf

I took a quick look at this one, and it seems my algorithm is a greatly improved version of what he is doing. The basic idea is the same, but he cannot handle shadow volume height and arbitrary retriever meshes. Very interesting link!

Nearest technique I know of (seen in terrain renderer):
-> Render terrain + Object casting shadow from above as a heightmap (using a RTT)
-> using resulting RTT heightmap in order to do some "heightfield self shadowing" (=> see below for a list)
-> then render terrain + object using resulting shadow map

heightfield self shadowing techniques:

• Fast Global Illumination on Dynamic Height Fields
• Scalable Height Field Self-Shadowing (previous version of the above)
• Fast Soft Shadows on Height Fields via Multi-Resolution Image Processing
• Fast Height-Field Rendering under Image-Based Lighting(not freely available)

Interesting, I am going to check these to see how many useful concepts I can grab from them.

Do you plan to release your leghting in to public?

Sure, it's not that much code anyway. When I have more, I'll release the demo and source. But I think anyone who seriously wants to use it, would make his own implementation in the end. The technique is more interesting than the implementation.

[Sgw32]

It's very interesting. What's is the perfomance of it?

it only works for games that are viewed from the top, like Diablo and Torchlight.

Does it work fast on them? Why we can't use it in other type of games, for example, shooters?