"artistic" Mode using Gmil

After the announcement of G2 by Worley Laboratories, I looked at the page describing the "art mode" and knew immediately how it was being done... the only question was how to test my theory.

I knew that the process involved a very simple idea: extend the surface normal from any given point to a point on a sphere and derive the color thereby. It's a kind of environment mapping, but drawn using the surface normal alone rather than angle of incidence/deflection, which is the norm for a reflection map. I suspected that this is what Gmil did, but only got to testing it now. And here it is.

And here is how it is done:

1. Create/obtain a source texture similar to the one in the G2 example. Any textures created for use with G2 will work.

2. Map it to the background using Textured Environment. Use Planar projection. You will need to size that texture slightly above 2 meters per side to get the coverage you want. Use the Z axis. This will aim the "hot spot" in the source image along the Z axis. You can also use a reference null if you need to re-orient the apparent lighting direction on the object (this method ignores actual scene lighting). Be sure to leave the null at the origin. Because of this projection method, the lighting will be duplicated from the far side, as you see here:

3. Load up a background image and put it in Compositing/Background (if you don't want to see the Textured Environment itself).

4. Load your object.

5. Set luminous to 100% and diffuse to 0. Set color to black.

6. Apply the Gmil shader. Use the following settings: Color Add = 1.0, Luminous Add 0. Set "Samples" to 0; this will shut off the occlusion/shadowing calculations and set Gmil to work strictly like the environmental shader I described above. Leave the rest as is.

7. Render. You should get the results I did above.

Notes: The main limitation here is that gmil uses the background, which is of course immortal (there can be only one!) To get the same effects with multiple surfaces using independent images, a surface-normal enviro mapper would do the trick (just like reflection maps, but using surface normals only).

There are also no restrictions on the projection method used for the background. Mine was intended to duplicate G2 using idential images; other images can be designed to use spherical or cylindrical projection, controlling the effect through a full 360 degrees.

Jim May/Court Jester Creations.
www.altyna.com

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