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Surrealist.
08-03-2005, 03:35 AM
Anyone noticed this?

Maybe I am just the last to know. I can't imagine I am Columbus here.

Anyway here goes for what it's worth:

Spotlights have a hard edge unless you increase the softedge angle using shadowmaps. Correct? OK. Well Area Lights give you soft edges but only under the following conditions, (with raytraced shadows of course) If the area light is far away or large in comparison to the object. Far away softens the shadows. Close sharpens them. larger light = softer shadows, smaller, sharper. OK? Good.

Now, increase the cone angle of a Spotlight with shadow maps and you get the same result- more or less.

The wider the cone angle the softer the shadows, but juist like area lights relative to the distance from the oject. So a spot light further away gives you a soft shadow at a more narow cone angle than a light that is closer which needs an extremely wide angle to achieve this. All assuming you have some soft edge applied. Shading Noise reduction is a help. This is 1/4 the render time of an area light.

OK. Am I just a moron? I have never heard of this.

This can't be a woo hoo big discovery, but I have never heard of it.

Captain Obvious
08-03-2005, 06:06 AM
Actually, the fact that spotlights produce "softer" shadows when you increase the cone angle is a render error, of sorts. When it generates the shadow map, it has only a certain amount of data it generates. The wider the cone angle, the thinner is this data spread out, resulting in less details. If you have some 'fuziness' to the shadow map, you decrease the horrible artifacts you get, and the shadows are, sort of, soft. However, if you look at the images you posted, you see that the shadow's fuzzy border is just as large where the distance between the sphere and floor is small as it is where the distance is large. This is, quite simply put, incorrect. With an area light, the fuzziness increases as the distance increases. With a spotlight, it doesn't.

Surrealist.
08-03-2005, 01:47 PM
Actually, the fact that spotlights produce "softer" shadows when you increase the cone angle is a render error, of sorts...


Well, thanks for the explanation and samples. I should haver been more specific though. I understand that this is unrealistic. But yor explanation explanes why, so thanks. :)

Edit: To be even more specific, I undersntand about the shadow distance going away from an object. This is something that is taught even in traditional art, that the shadow becomes more soft going away from the object. However this is really only a blantant factor when the shadow from an object is resting on the ground and you can compare. Not all shadows are going be from objects resting directly on the ground.

I also understand about it not being realistic in either case. Tradoffs in time verses realistic are all through art not just CGI. Shadownaps are unrealistic period as are some radiosity settings. It's about tradoffs and your specific needs on a project by project, shot by shot basis.

We could all sit around and argue what's real for days. That's not the point.

My qeustion really is that in all of the tips I have seen regarding soft edge shadows, why not this? I have been asleep or never noticed or what?

It's just too obvious. So I don't understand why It was never mentioned.

Speaking of obvious, capt. The reason your area light shadow is noisy has to do with mainly not having turned on shading noise reduction. Then the distance to the object and the area light size also play a role. :)

Captain Obvious
08-03-2005, 03:26 PM
Oh, I've used soft-shadowed spotlights instead of area lights myself, to save on render time. I understand your point, I just figured I'd clarify. ;) It's always a compromise.




My qeustion really is that in all of the tips I have seen regarding soft edge shadows, why not this? I have been asleep or never noticed or what?

It's just too obvious. So I don't understand why It was never mentioned.
I guess most people figured that it was obvious enough not to mention. :p




Speaking of obvious, capt. The reason your area light shadow is noisy has to do with mainly not having turned on shading noise reduction.
I know. I don't like shading noise reduction. I'd rather turn up the anti-aliasing and wait longer, or fix it in post. ;)

Surrealist.
08-03-2005, 03:34 PM
Cool thanks again for the clarification. Intersting to see people's different approaches and works flow. Cool. I was just giing you a hard time aout noise reduction. I knew you knew about that. :)