AO without AO

[robcat2075]

This is a little try at making an AO style render with just z-buffered kleig lights.

 

I chose the "Biobot" character from the extras disk because he has lots of crevices and bumps to challenge the occlusion effect.

 

 

AOBTurnTestH.mov

 

 

The result isn't quite as satisfying as a real AO image but it takes only 5 seconds per frame to render.

 

The quicktime compression is making the shadows on the ground look patchier than they really are. In the original render they're quite smooth.

[jason1025]

This is a little try at making an AO style render with just z-buffered kleig lights.

 

I chose the "Biobot" character from the extras disk because he has lots of crevices and bumps to challenge the occlusion effect.

 

 

AOBTurnTestH.mov

 

 

The result isn't quite as satisfying as a real AO image but it takes only 5 seconds per frame to render.

 

The quicktime compression is making the shadows on the ground look patchier than they really are. In the original render they're quite smooth.

 

Sweet render.

 

I hope to see a Vtut when you perfect it.

[serg2]

Nice idea! Thank robcat2075

[John Bigboote]

Cool and quick! I'd be interested in the setup....

[zandoriastudios]

FYI: when using multipass, AM jitters the the light position between the passes based on the WIDTH property of the light.

This feature happened after the era of Yves' skylights or John's Skycast, so you may not be aware of how it changes things:

 

Try this: a simple 9 light skydome with bulb lights with multipass--You would expect to see the overlapping shadows with so few lights (and that used to be true), But with multipass the jittered positions of the lights create the same effect as you would get by adding additional lights to the skylight rig (equal to the actual lights x the number of passes!).

[HomeSlice]

Excellent tip. Thanks Will.

[John Bigboote]

Try this: a simple 9 light skydome with bulb lights with multipass--You would expect to see the overlapping shadows with so few lights (and that used to be true), But with multipass the jittered positions of the lights create the same effect as you would get by adding additional lights to the skylight rig (equal to the actual lights x the number of passes!).

 

Does this effect become greater by scaling the width of the lights up then?

[robcat2075]

I like the self jittering lights. There's an issue when the "width" is greater than 0, the shadows cast by a z-buffered kleig light don't reach into that extra width. So an object moving across the light cone would not cast a shadow near the edge. The larger the width, the greater the non-shadowed space.

 

 

I've AMreported it as a bug. V11.1 kleig lights didn't do that. V11.1 lights had a instant jitter if you turned on "penumbra" that worked without multipass, but it was only about 5 jitters.

[zandoriastudios]

I use BULB lights for the skydome.

[thejobe]

i think this is basicly what he was talking about with skylights and multi passing

first one is with only 2 passes and 8 light setup (9 secs per frame)

second one is with 9 passes (3x3 softing on) and 25 light setup (36 secs per frame)

each light is a bulb with 50 rays cast for shadows

NO_AO__AO.mov

NO_AO__AOb.mov

[mtpeak2]

Robert, do you have a prj you can post, so we can see how you set it up?

[robcat2075]

Robert, do you have a prj you can post, so we can see how you set it up?

 

Well that would be giving the secret trick away!

[Eric2575]

Wow, yu be reelly smart to do fancy light and show we be reely dumb for not knowing light...um me forgot to say seeeecret light trick.

 

Nice one 2075

[Xtaz]

Robert ... I think you are using the same principle of MUFOOF .. aren't you???

[robcat2075]

The example I show at the top of the thread doesn't use multi-pass. My goal was to see what's the fastest I could get "that look" to render so i wanted to get it all in one pass.

 

There is an array of about 9 lights around the character. That's enough to get an AO-ish appearance on him. They are light-listed to only illuminate the character however; they don't create the shadow on the ground. If they did, you'd see the typical multi-shadow on the ground plane that light arrays produce. You don't see the multi-shadow on the character so much because he's a complex shape.

 

The ground shadow is one VERY hazy shadow-only light from above and a few negative lights positioned around his toes and ankles to add extra darkness to the ground where his feet would be occluding the ground more. The negative lights are light listed to only affect the ground plane.

 

A couple more negative lights are aimed UP from the ground to darken the undersides of his feet where the ground would be occluding them in return, particularly the foot on the ground which needed that to look like it really was on the ground. Those are light listed to only "shine" on the character and falloff quickly so they don't go project farther onto the main body.

 

So far, there is no actual light falling on the ground plane. One sun light with shadows OFF is added and light-listed to shine only on the ground. A wide Kleig light would have worked just as well. It lights the whole plane evenly and doesn't even matter which way it is pointing. The shadows that appear on the ground are the result of the shadow only lights and the negative lights subtracting brightness out of the ground plane. Because the shadows are all simple depth mapped shadows they render VERY fast.

 

If you move the character his foot shadows won't follow him, but that could be fixed for animation by constraining the negative lights to him.

 

Yes it is a trick, but it got the shot rendered in record time, good enough to look like what it was supposed to look like.

 

That's the big take-away I get from the Birn book; there's whole bunch of tools in CG lighting that dont' exist in nature but you can use them to get your natural looking result faster, and faster is better because it gives you more time to tweak.

 

The down side is you have to know what you want before hand. I sort of knew what AO should look like in this set up. In a more complex scene I'd be less certain.

 

 

Here's the PRJ, secret stuff and all!

 

Biobot08i_turnaround_new_Ring.zip

 

 

There's currently a bug in v15i that causes models to lose their light lists if you swap a proxy in or out. That will be fixed in the next version.

[NancyGormezano]

I wonder, if for another trick - (probably wouldn't work so well for animation, or flat surfaces) - if using AO rendered plain sphere image for a matcap shader, if one might be able to obtain a pseudo-ish AO render. Matcap is plenty durn quick.

[mtpeak2]

Thanks Robert.

[serg2]

I wonder, if for another trick - (probably wouldn't work so well for animation, or flat surfaces) - if using AO rendered plain sphere image for a matcap shader, if one might be able to obtain a pseudo-ish AO render. Matcap is plenty durn quick.

 

It cool idea Nancy!

 

[John Bigboote]

Wow. I gotta revisit that Matcap thread... GREAT looking model Serg...where have you been? That would have done well in our mascot contest!