[osg-users] Multipass Technique

[Alex Taylor]

Hi all,

I'm interested in trying out the MultiPassTechnique for for volume
rendering and I have a few questions after looking through the source code
and the example.

1) In the example, here is the description of the convex hull that can be
used by MultipassTechnique:

--hull","load 3D hull that defines the extents of the region to volume
render.

The hull is then read in from a file, if specified. My first question is,
what is the expected form of the geometry that one adds to the Tile via
addChild? It's not clear to me in the example without seeing an example of
a file that contains a hull.

2) There are different shaders and enums for three different scenarios:
CUBE, HULL, and CUBE AND HULL. What do each of these scenarios mean? When
would each be useful?

3) I'm interested in Multi-pass technique because I'd like to be able to
implement a clipping "ROI" defined by an data-axes aligned cube. Would it
be possible to define a cube shaped convex hull and have the portion of my
data that is inside be rendered and have the portion outside the cube be
clipped? Is this within the use cases that were in mind when Multipass
Technique was added?

I appreciate any help people can give me, I'd really like to get started
with MultipassTechnique, looks like a good addition to the library.

- Alex
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