Big List of Questions about Java3D

[Zachary1234]

I have some questions about acheiving certain tasks in java3D.
I will be replying to this thread later with more details examples.
Is there anyone here who can spend time giving me some code example and related answers to these?

[Rick Fincher]

Are you trying to decide whether or not to use Java 3D? From your
questions it looks like you haven't read any of the documentation and
don't understand the concept of scene graphs.

Everything in Java 3D is done with a database called a scene graph. You
add nodes and branches to a scene graph that define points, lines,
polygons, text, and surfaces. With a surface you have to define a
vector that tells Java 3D which way is the "outside" of the surface so
that it can tell if the observer can see it or not.

Java 3D handles all the clipping and hidden line and hidden surface removal.

Java 3D relies on an external library to quickly draw the primitives.
Open GL, JOGL, and Direct 3D are used depending on which OS you are using.

You can set the colors, line thicknesses, and transparency of each
branch. You can also map images onto surfaces, as well as define the
surface texture and reflectivity (shiny or matte) models.

You can translate, rotate, scale, etc. each branch independently. If
you have a car as a branch of your scene graph, for example, you can
create a "tire" branch, make 4 copies of it, add them to the "car"
branch then translate and rotate the tires to put them in the 4
locations needed. Then you can start the tire branches rotating at
whatever speed you like .

Then you can move the the car branch to make the car move around with
the wheels rotating.

There is also a collision detection mechanism so you can tell if two
objects occupy the same space at the same time. That's used a lot for
gaming.

Rick


On 4/22/2012 7:55 AM, Zachary1234 wrote:

[Zachary1234]

I am hoping I can have a correspondance here, a place to reply with further questions to answers.

-How do I draw the outline of a 2D circle, placed, sized, tilted anywhere
in a 3D Universe? How may I fill that circle with two colors on either side?

-How May I construct a 2D plane from any 3 (x,y,z) points? How
may I determine if any further 3D points are in my plane?

-How may I define a line segment from two points, anywhere in a 3D universe? May I go setCollidable(true) on my line?

-May I fill a GeometryArray with consecutive 3D points to define a surface in (Ploygon) 3D? How do I tell my first point to meet my last point? Is this in fact the way to do this?

[Rick Fincher]

This is a NetBeans forum, not Java 3D, so I'll email you directly.

Rick

On 4/23/2012 6:39 AM, Zachary1234 wrote:

[emiddio-frontier]

i was interested in the answer also.

Gary
----- Original Message -----
From: "Rick Fincher" <address-removed>
To: <address-removed>
Sent: Monday, April 23, 2012 2:17 PM
Subject: [nbusers] Re: Big List of Questions about Java3D


This is a NetBeans forum, not Java 3D, so I'll email you directly.

Rick

On 4/23/2012 6:39 AM, Zachary1234 wrote:

[Zachary1234]

It's alright, most of the questions on this list won't be required.
It turns out that the java3D pdf tutorial collection freely available
via the internet is mostly enough. Many of these questions won't be required; I will be replying to this thread later. They can be removed, if anyone on this thread wants.

[Zachary1234]

Could someone please give responses with code specific answers?

#A I have a set of points, to be connected as lines, and to be formed into surfaces (limited planes) as defined by my IndexedQuadArray and IndexedTriangleArray.

#1 I don't understand how the function IndexedGeometryArray.setTextureCoordinateIndexes(int a,int b,int [] c);
works. What is the int value I would submit for the first parameter,
texCoordSet - texture coordinate set in this geometry array? Is it how to arrange the texture, {0,1,2,3} ?

#2 I understand how I may use the NormalGenerator class over an appropriate GemoetryArray to connect points as curved lines,curved triangles or curved squares depending on the array. One may alter the crease angle by a radian, however the crease will always be located centrally on the curve (curved line or triangle/square surface as generated).

Apart from introducing more curves in the same region
to define a net result differently, how does one alter the (relative) crease location? How else may one define and alter curved lines and generated surfaces existing between points inside a GeometryArray?

#3 How may I define a circle or an oval (flat, 2D) in a 3D space?

#4 When using a GeometryArray and NormalGenerator to generate my surfaces, how may I define hole regions on a surface which is not filled in at rendering, but does not effect the generated normalisation shape?

#5 Is there a way to obtain one object for a Triangular or Square surface generated inside a Geometry Array? What is the Generic class or Interface for this named? May one test if a particular (x,y,z) point lines
as a normal (on/in) this surface, either before normalisation or after it?

#6 When using IndexedGeometryArray (s), at run time there is a situation where non-visible regions of a 3D world objects aren't filled in or rendered as wireframe or points as a memory save. However,
the priority is "backwards" by default; . Without disabling culling entirely, is there a way to have the memory save of some non-filling or wireframe drawing happening by allowing rendering of the outward facing polygons only (not the behind faces), or even just the visible ones from the viewer perspective? Or does use PolygonAttributes to turn off culling entirely, and this optimisation in fact happens by default?

#7 How does one translate a point in the direction of another one, presumably by a 3D vector? How may this be done in the direction of the other point, one pixel at a time, and not the full distance between them (easy) ?

#8 When viewing against the background of a 3D Universe, is there any way to increase the outer pixel resolution of an object to acheive some antialiasing?

#9 How do I disable the default shadow of a 3D object via it's lightsource, to do high quality shadowing? I know that shadowing is typically done per pixel, point. A shadow is a linear cutoff of the projected lighting region. Need to know the line from the light source, get a vector,
and draw lines to points & objects behind. Suggestions?

[Glenn Holmer]

On Thu, 2012-04-26 at 05:33 +0000, Zachary1234 wrote:

[Zachary1234]

Yes it is, however it is a forum for java related questions,
even if I havn't unfortunately found the correct area for that
(there doesn't seem to be a forum area labeled java SE,
or general java code questions, or even java3D).

Is there anyone out there who can address my questions raised?

[Matthias Bl]

Hey,

Am Mittwoch, den 02.05.2012, 01:22 +0000 schrieb Zachary1234: