Jim Holsenback <jho### [at] povrayorg> wrote:
> I've been giving Trevors crevice grime macro a try and I think I'm
> getting the hang of it. The three objects on the pedestals have an
> object light that was used to fill in the areas that the overhead and
> mezzanine lights didn't reach. I started getting better results when I
> used the location of each objects light as the grime macros "camera
> location" instead of the scene camera location.

It looks good.  Nice to see some usage out of it.

The way the macro works, you may get artifacts doing this depending on how much
the location varies from the angle. Areas that are 'shadowed' by the tracees
would be evident, also the grime pattern will be projected through to the
backside of the object unless methods are used to avoid this.

With 'proper' settings it *should* work just fine and probably best using the
camera location for this reason.  However what 'proper' settings are are up to
the user/artists/beholder to figure out.

Generally:
-increase surface offset for meshes to avoid catching the mesh corners.  the
size of this required will depend upon the curvature and resolution of the mesh

-try to figure if you want to capture shallow areas or not, for shallower
grooves, use lower angles.  I have been using anything from 5-20deg depending on
what I want

- try to figure the groove size you want.  This is going to be relative to the
model size again.  I have been using ~2-10% of the object height.

For example, for my buddha:
object height = 200
recursion level min=2
recursion level max=4
resolution = 1000 for 1920x1080 final image
I also have truned on linera interpolation

for crevices:
control angle = 5deg
control depth = 20
offset = 0.05

for edges:
control depth = -20deg
control depth = 15
offset = -0.01



I will probably be posting an update version soon, which I have added a some
optimisation and added features.


> Now a question (the real reason of this post) ... what's up with the
> slightly tilted look (back and forth) with the Moai. My camera's look_at
> is 180 from it's origin, so it's flat. The angle is default. I'd like to
> be able to solve this without a lot of trial and error. My 1st thought
> was rotate a little x (cam is at -z) but was wondering if changing the
> look_at y vector just a tad was better ... Or maybe I should pull the
> camera back and make angle smaller.

What you are seeing is probably perspective distortion.  For example look at how
the shape of the floor tiles looks at the corners of the image vs the center.
The way to minimize this is to pull your camera back and tighten the view angle,
nuch like zooming in real photography.



>
> Hey if there's a "teaching moment" out there ... I'm all ears.
>
> Jim
>
> PS: don't be giving me the gears about the dark walls ... I'm workin' on
> it ;-)

-tgq

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