PDA

View Full Version : Lighting without Light



dpont
12-14-2007, 08:05 AM
Nothing revolutionary,
a basic teapot from Modeler, a NULL as Light reference,
used with Spot to build a direction for normal in
Occlusion node in DP_Kit (or directly used as Target
with Directional option in SG_AmbOcclusion),
direction is coupled with Spot Smoothed Normal
to build a basic Lambert Diffuse Model,
A small Angle of 10 in Occlusion node gives
nice soft shadows.

53093

Thanks to Simon Lundberg for scene and first input.
Denis.

dpont
12-14-2007, 08:42 AM
You could use Pom's Ambient Occlusion node too,
it has not normal input, but DP_Kit has a Replace Spot node
in Processing tab, to replace positions and normal,

53095

Denis.

Matt
12-14-2007, 09:59 AM
Am I reading this right? You are controlling the direction of the ambient occlusion by linking it to a NULLs position?

dpont
12-14-2007, 10:04 AM
...With the substraction of the Spot world position
to give a pseudo light direction, this is for replacing
the normal of Spot to orient the Occlusion cone/hemisphere.

Denis.

Captain Obvious
12-14-2007, 10:08 AM
Yep, that's right. This is a technique I've been experimenting with when I realized that GI was too slow for an animation we're working on. I will post more information and maybe a tutorial when I've done more work on it.

dpont
12-14-2007, 10:41 AM
In fact, amb occlusion is not convincing to fake
entirely lighting on the teapot, even with SubD mesh.

Since raytracing hit real polys, self (occluded) shadows
reveal flat/unsmoothed geometry, when the light direction
becomes tangential to the polygon,
that's why a Diffuse Model is important to cover
the areas of the mesh, which are opposite to the pseudo light.

Note that a bit higher "Shift" is helping a lot to
avoid unsmoothed polys.

Denis.

oldtekerr
12-14-2007, 10:57 AM
Xsi has this feature. Captain, High mes and directional occlusion is a great idea. I just watched some training for xsi that used that technique with great results...

dpont
12-14-2007, 11:01 AM
Here, the teapot has med/low res, no SubD,
without Diffusion Shading you get this:

53101

Denis.

oldtekerr
12-14-2007, 11:26 AM
To add to that... for an interior you will need to use a distance to gradient to fade from directional to nondirectional for good results...

Iain
12-14-2007, 06:09 PM
Yep, that's right. This is a technique I've been experimenting with when I realized that GI was too slow for an animation we're working on. I will post more information and maybe a tutorial when I've done more work on it.

Can we see any of your results in a production scenario?

Captain Obvious
12-17-2007, 05:43 AM
Can we see any of your results in a production scenario?
Not yet, no. Once it's in the public, I will show you whatever I can.

Captain Obvious
01-15-2008, 03:24 AM
You could use Pom's Ambient Occlusion node too,
it has not normal input, but DP_Kit has a Replace Spot node
in Processing tab, to replace positions and normal,

53095

Denis.
What does the Replace Spot node actually do?

dpont
01-15-2008, 05:06 AM
Replace Spot node let you replace a few
Spot input like smoothed normal or world position,
in case you replace them directly in the input
of the node, i.e: LW Occlusion node hasn't not
normal input.
Replace Spot node must be set after the node
or node chain you want modify.

Denis.

Captain Obvious
01-15-2008, 06:04 AM
Ahh, that makes sense.

dpont
01-15-2008, 06:45 AM
Edit:...Was too fast with my typos:

"in case you (can't) replace them directly in the input
of the node..."

Denis.

Captain Obvious
01-15-2008, 08:11 AM
So basically, it means you can take a node that doesn't have a position or normal input, plug it into the Replace Spot node and transform the current spot being shaded?

dpont
01-15-2008, 10:02 AM
Yes,
I made also some testing with Extrabuffer nodes,
storing Spot position & normal in Store ExtraBuffer
for object in scene,
output these buffers in Pixel Image Filter node editor,
and using Replace Spot node to apply a procedural texture
on the 3D object in a post process.

Denis.

gerardstrada
01-15-2008, 01:45 PM
Xsi has this feature. Captain, High mes and directional occlusion is a great idea. I just watched some training for xsi that used that technique with great results...

SG_AmbOcc node has always had directional occlusion. What Denis' node configurations does is to simulate a diffuse model (lambertian) without lights. Which is interesting... :)



Gerardo

Captain Obvious
01-16-2008, 03:17 AM
One problem with this lighting method is that it's a pain in the arse to set up, especially for scenes that have already been textured. And once it has been set up, changing it is a pain if you have a lot of surfaces. So I had this idea!

Suppose there was a Shader (as in a non-nodal shader) that, whenever a spot is shaded, basically grabs the Diffuse Shading from a surface of your choice (keeping the spot info unmodified, obviously), and uses that as illumination. So if you have a regular, non-nodal surface with the "Grab Shading" non-nodal shader set to grab illumination from a different surface, that surface will then sample the same point but with the target surface's diffuse shading output, and use that as diffuse illumination.

That way, you could have one surface with the occlusion lighting applied, and just add the "Grab Shading" shader to all the other surfaces, maintaining old texturing.

Would such a thing be possible within LW's SDK?

Captain Obvious
01-23-2008, 06:02 AM
Maybe I'm just confused, but I can't find the "replace spot" node in the DP_Kit.

gerardstrada
01-23-2008, 06:06 AM
It's in processing tab.



Gerardo

Captain Obvious
01-23-2008, 02:04 PM
I can't find it :(

gerardstrada
01-23-2008, 07:11 PM
It seems it's not the lastest version of DPKit.
Btw, you should install the ExtraBuffers nodes (they are in Processing tab too, but aren't compiled in DPKit plugin).



Gerardo