3ds max - removing AO from skylight in a matte/shadow plane

l1kel1ke

Hey guys, I'm wondering if there is a way to disable the AO of a skylight while preserving the illumination?

I am using an environment with a matte/shadow plane underneath assets to render them out with an alpha and a single shadow, but I use a skylight to get the softening ambient light on everything... which is proving to be a problem because it casts a very light layer of shadow that's interfering with packing the textures and aligning sprites (via texture packer).


I've selected the matte/shadow plane and excluded it from all advanced lighting calculations in object properties, as well as disabled illumination from final gather and pretty much everything in the mental ray tab just to be safe. I'm still having this issue, however.

any ideas? I've tried fiddling with options and render settings and it hasn't really helped. The only thing that 'works' is when i completely remove the skylight in the scene and crank up the ambient global lighting in environment settings, but it changes the way the assets render out, and as many of the other assets we plan to use are already rendered out in this light environment (they're fine as they didn't require a static shadow), i'm hoping to find a solution while keeping the skylight.

I'm using the default max renderer (scanline) for this btw. any help is appreciated!

here's a screengrab of the issue at hand. I had to blow it up in photoshop for it to be visible, but even at the single render level it's still causing an issue for texture packer.

Memory

I'm wondering if there is a way to disable the AO of a skylight while preserving the illumination?

To get exactly what you've described here, just turn off "Cast Shadows" in the "Render" area of your skylight. That would give you the illumination from the skylight with no AO. Another way to get your illumination without adjusting the global lighting would be on an individual material basis--just drag up the spinner for self-illumination.

In any way you do it, subtlety is going to give you the best result.

l1kel1ke

thanks for your help! that actually did the trick, but now I realize that the ambient occlusion on the actual object made it look LOADS better, and without it the illumination of the skylight doesn't really provide a sufficient softness. With that, is there any way for me to preserve the illumination AND the AO of the skylight on certain objects but disable it for the matte shadow plane? (so the plane isn't affected by the skylight at all - neither illumination nor AO, but everything else is?)

thank you again!

Memory

I found this on another site, generally what you're trying to do is not possible because of how global illumination/AO and all that jazz is calculated (from what I read)

I did find a way to exclude an object from being lit by a skylight but only if you are using the default scanline renderer.

You can do this by going to Rendering -> Advanced Lighting -> Light tracer. You should now see the advanced lighting section open up in the render scene window. Adjust the settings here(I suggest turning up the "Subdivide Down To:" option to at least 8x8) otherwise you get non-pleasing results.

This will cause all of the objects to be lit by the skylight and if you hit render, you should see some Global Illumination going on in the scene.

If you now right click on the object you want to exclude and select properties, go to the "Adv Lighting" tab and check the box "Exclude from Adv. Lighting Calculations" and click OK, this will exclude the object from being lit by the skylight.

I was able to get it to work by doing that, but my render did look kinda crappy compared to just using skylight with shadows on and not light tracer. Maybe you can make yours look better, I haven't really messed with light tracer much. You have other options though too, but they might be a little more work. You can always render the shadow you want separate (with the skylight off) and put them together in photoshop. This would be really easy if your shadow never moved.

That's all I got...

Teclis

I think i have a none propper solution, but it might work for your situation.
You could try rendering to images one with skylight, one without it. You'll get the a perfekt alpha mask for the one without skylight. So you can easylie composite it.