Mike,
1. Image
The image is pasted into the top-left of the Canvas3D window. It doesn't
respond to window resizing or View changes in any way (that I know of...).
2. Geometry
As the geometry is defined at infinite distance Java 3D does not have to do
any perspective or depth calculations before it draws the geometry.
I.e.:
- draw background image
- draw background geometry
- draw opaque objects
- etc...
I have used a Sphere primitive (flip the normals - you're *inside* it...)
with a texture map applied to it to good effect for defining sky/mountains
etc.
Hope that helps, it's getting late.
Sincerely,
Daniel Selman
[EMAIL PROTECTED]
http://www.tornadolabs.com
-----Original Message-----
From: Discussion list for Java 3D API
[mailto:[EMAIL PROTECTED]]On Behalf Of Mike Gardner
Sent: 13 January 2000 18:17
To: [EMAIL PROTECTED]
Subject: [JAVA3D] Background node specification
I am having a problem understanding the specification of the Background
node.
My application displays a real landscape. "Close" objects are displayed
via the scene graph in the normal way. I intend to display objects (such
as mountains) that are further away than the back clip distance via a
Background node.
With a Background node I have two options, I can use an image and/or
geometry.
Let's start with the background image. The Background node javadoc just
says, "The Background leaf node defines either a solid background color or
a background image that is used to fill the window at the beginning of each
new frame". Are the edges of the image aligned with the virtual world or
aligned to the View (if so, which View)? How is the image scaled relative
to the "window"? I could find these things out by experiment of course,
but I'm not happy committing a lot of work to something which could change
completely in a future J3D release.
Now the geometry. The Background node javadoc says "It optionally allows
background geometry---which is pre-tessellated onto a unit sphere and is
drawn at infinity---to be referenced." A previous version of the javadoc
said, "It optionally allows background geometry to be referenced.
Background geometry must be pre-tessellated onto a unit sphere and is drawn
at infinity."
Neither are very clear. Why is a _unit_ sphere required? Do all the
geometry vertices have to be at unit distance? What does tessellated mean
in this context? Does it mean that the geometry has to cover the whole
sphere? It would make sense for all the geometry to be _projected_ onto a
sphere at infinity. By experimenting I have been able to create certain
types of Background geometry but not others.
This makes me nervous enough to want to avoid Background nodes altogether,
but unfortunately this is the only way I can think of to display far
landscape objects.
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