[sldev] Sculpties: Vacuum-Forming, Skittering, Zone Linking

[Dale Mahalko]

(Whoops, I replied to this only to Kent, when I was intending to reply to
the list..)

On 9/28/07, Kent Quirk (Q Linden) < q at lindenlab.com> wrote:

> The problem with your statement about having points potentially very far
> apart is that you never want really big triangles in your rendering
> system. They tend to do nasty things with clipping, lighting and the
> like, so practically the "maximum" distance between points in triangles
> is pretty short.


In the event that a low-detail section of a sculptie surface is too large
for easy clipping/rendering, you could allow for the client to subdivide
very large surface into smaller, easier-to-process triangles.

>From a quick verify in wireframe rendering mode, I see that this is already
being done with SL's primitives. A 10m x 10m x 10m cube automatically has
each face subdivided into nine 3.33m x 3.33 x 3.33m squares and 18 triangles
by my client.




> In a system designed to be used by normal people (as opposed to 3d
> modeling specialists), I would not *ever* be inclined to expose
> individual triangles or vertices for user editing. It's just too easy to
> create whacky results by dragging vertices across triangle boundaries
> and the like. That way lies madness.


With skittering, the objects that make up the shape inside are effectively
treated as a single unified mesh via constructive geometry adding all pieces
into a single ultra-complex mesh. The surface of this ultramesh is used as a
constraint for the sculptie vertexes moving over its surface, with an
elastic flexibility to how closely the sculptie vertexes match the
underlying ultramesh.

I don't envision the user being able to drag individual points off of the
underlying shape and sticking them out in midair with nothing underneath to
"support" the vertex. Likewise pushing a random vertex into/below the
ultramesh would not be allowed.

The vertex dragging/skittering operation would be similar to painting a
texture onto a shaped 3D object, where the paintbrush is only able to move
across the object in a manner that is constrained to the surface of the
object and the user's current camera view of the object. There is no typical
flat "working plane" concept here, and instead the surface of the entire
underlying ultramesh is used as the working plane for the sculptie vertexes,
greatly limiting the potential madness.

-Dale
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