No shadow on splines

[Tore]

When a light’s shadow option is set to ray trace, “render as lines” splines do not cast any shadow.

Is this an error (that should be reported) or is it a (missing) functionality?

[robcat2075]

Does it work with z-buffer?

 

I would not expect it to work at all since splines are infinitely thin and the "line" is probably painted onto them as a sort of post effect.

[Tore]

Does it work with z-buffer?

 

I would not expect it to work at all since splines are infinitely thin and the "line" is probably painted onto them as a sort of post effect.

 

Yes, it does, strangely enough, work with a z-buffered light!

[Tore]

[robcat2075]

interesting. I suppose the techref doesn't say anything in this regard.

 

Is there a reason Z-buffer won't work for your shot?

[Tore]

I never use z-buffer shadows - they are imo unpredictible and unnatural looking. And sometimes produce strange stuff, like the hole in the hat (which in reality is totally massive), as seen on the attached pics.

 

[Tore]

The TECHREF has this to say about "Render as lines" (nothing that indicate that shadows shoukdn't work):

 

"One of the objectionable artifacts of computer rendering is the broken-up

appearance of very thin geometry. For example, the ropes on a Spanish

galleon are necessarily long and very, very thin, which causes them to

break up and temporal alias (chatter) during an animation. This

phenomenon results from the fact that rendering resolution is not infinite.

Animation:Master’s a-buffer renderer alleviates the problem somewhat but

the discrepancies often still manifest themselves.

A "line" geometry type should be used for long, thin lines; like whiskers of a

cat, or antennas on a butterfly. When you are modeling, use splines to

represent the long, thin geometry (don’t make valid patches). Then group

the control points that make up the long, thin geometry and name the group.

Animate the splines as you wish. (The "Line" option should not be used on

groups that contain patches). When this property is "ON" the surface

property contains the options you can use to set the lines look.

These options include Color, Width and Transparency. Randomness,

which controls how squiggly the line is. Randomness Scale, which controls

the size of the squiggles. Glow, which with randomness can give the effect

of lightning."

[robcat2075]

You might report it to A:M reports.

 

There's usually a solution for z-buffer problems. The hat hole may be a bias setting that is too high.

 

For now, you could use a shadow-only z-buffered light and light lists to get a shadow for the spline and use ray traced lights for everything else.

[Tore]

For now, you could use a shadow-only z-buffered light and light lists to get a shadow for the spline and use ray traced lights for everything else.

 

That's a great idea! Hadn't thought of that!

 

Thanks Rob! :-)

[robcat2075]

If you haven't read it already, Jeremy Birn's "Digital Lighting and Rendering" is a good book for ideas on how to work with CG lighting.

 

(I see he's just come out with a 3rd edition. My notes are on his 2nd edition)

[Tore]

Yes, those are great books! I bought both first and second edition, but didn't know that a third was out. Well that's one more for the wish list :-)