Paul Kim - Translucency

t r an s l u c e n c y

The images and renders on this page demonstrate how using multiple lights and shaders can create a translucency effect,
as shown in the palmetto fronds from the pre-baked ribs assignment.

For this assignment, we took the pre-baked ribs from a previous assignment
and applied lights and shadows to create a translucent effect.

Using a diffuse shader, we were able to create a lighting atmosphere
that would allow front and back lighting.

In class, we applied the shader to simple polygons to see the effect
of the translucency.

This was renderd with a shading rate of 50, so lower the render time.
Even so, I think it turned out pretty good.

Here is the script for that:
surface translucency(float Kdfront = 1,
Kdback = 1,
backlighting = 0.5;
color tipcolor = color(1,0,0) )
{
color surfcolor = mix(Cs, tipcolor, t);
normal n = normalize(N);
normal nf = faceforward(n, I);
Oi = Os;
color front = Kdfront * diffuse(nf);
color back = Kdback * diffuse(-nf);
color diffusecolor = Kdfront * diffuse(nf);
Ci = Oi * surfcolor * mix(front, back, backlighting);
}

The RIB file used for this was the one provided by Professor Kesson.
I tried to use my own palmetto group, but I kept getting errors
in both Cutter and Maya.
Here is the error I get in Cutter:
Z10002 {WARNING} Primitive pCube1|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube2|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube3|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube4|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube5|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube6|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube7|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube8|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube9|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube10|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube11|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube12|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube13|pCubeShape1 is not visible to camera or traced rays.
Z10002 {WARNING} Primitive pCube14|pCubeShape1 is not visible to camera or traced rays.
R12001 {ERROR} File RIB_Archive/palmetto_mid_rigged_2.0064.rib cannot be opened by RiReadArchive.
[{Splitting} Object:'pCube13|pCubeShape1' ] (System Error: No such file or directory)
***The {} used above where it says {Scripting} are actually <> but the formatting of the html sees them as scripting.

In Maya. these are the errors I get:
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0089.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube38|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0068.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube39|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0010.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube20|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0017.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube24|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0066.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube26|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0079.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube21|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0087.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube25|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0072.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube17|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0038.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube23|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0074.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube30|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0041.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube1|pCubeShape1' ] //
// Error: (02/19 18:07) rman Error: R12001 File RIB_Archive/5/palmetto_grouped_2.0002.rib cannot be opened by RiReadArchive. [{Splitting} Object:'pCube16|pCubeShape1' ] //
***Again, with the {}, they are supposed to be <>.

I am completely lost as to what these errors mean. The RIBs were working
just fine for the Pre-Baked RIB assignment, but when I tried to render
them out again, they were not working, hence the errors.

This took forever to figure out. It took many trials and errors
with renders that would only show the blotchyness without the
lighting, or just the lighting without the blotchyness.

A quick side note: I chose to use the color red so that the
results could be seen better in the testing phases and they are
by no means meant to portray a realistic coloration of the
palmetto fronds.

I was then able to apply a blotchy texture to it in conjunction
with the translucency lighting. This was accomplished by referring
back to the noise shader we used for the animated pattern.

~~I was unable to figure out how to only get the tips to be red.~~

Using the new techniques learned in class, I was able to obtain the red
tips, as well as the blotchyness.

color surfcolor = mix(Cs, tipcolor, pow(t,tipstrength));
color speccolor = specular(nf, normalize(-I), roughness) * mapvalue * Ks * hilightcolor;
Ci = Oi * surfcolor * (ambientcolor + mix(front, back, backlighting));

Here you can see the tips being red, as well as the gradual coloration
towards it.

And here we have a more realistic color choice in the tips.
I also used an ambient light to get rid of some shadowing
as well as rotated the camera around the Y-Axis to achieve
a more interesting composition.