How to display polygons both with line contour and filled interior?

Question

How to display polygons both with line contour and filled interior?
Java3D 1.3, Java 1.4.1-rc

Answer 1

Hi,
I just started with Java3D last week.
I assume you mean drawing polygons with outlines (wireframe) in one color and polygon face filling with another color. If so, I've got the same question! (I usually think of "contour" to refers to plotting surface intensity of independent data like temperature or elevation, but I don't think you mean this.)
The only solution I've found so far is to make two shapes with the same geometry.
Here's an example - an outlined and filled cube. I made it using a generalize class DualShape which is two shapes with the same geometry, but one filled and one as a line.
It works, although I can't say I understand the setPolygonOffset(), knowing what value to set. Without the command, the depthbuffer can't consistently decide which should be in front between the fills and lines so it looks bad.
I certainly think it would be nicer to do both internally, like:
pa.setPolygonMode(pa.POLYGON_LINE || pa.POLYGON_FILL);
And then have setFillColor and setLineColor for each.
I don't know why they don't allow this - maybe OpenGL can't do it like this so Java3D follows.
If anyone has any better ideas I'd like to hear about it.
Tom Ruen
class DualCube extends DualShape // cube with outline and fill colors
public DualCube(float ax, float ay, float az, //cube lower corner
float bx, float by, float bz, //cube upper corner
float br, float bg, float bb, //border color
float fr, float fg, float fb) //fill color
setGeometry(new CubeGeometry(ax,ay,az,bx,by,bz),br,bg,bb,fr,fg,fb);
class DualShape extends BranchGroup //general shape with outline and fill colors
Appearance ap1,ap2;
PolygonAttributes pa1,pa2;
ColoringAttributes ca1,ca2;
Shape3D s1,s2;
public void setGeometry(Geometry geo, float br, float bg, float bb, float fr, float fg, float fb)
//filled shape:
addChild(s1=new Shape3D(geo, ap1=new Appearance()));
ap1.setPolygonAttributes(pa1=new PolygonAttributes()); pa1.setPolygonMode(pa1.POLYGON_FILL);
ap1.setColoringAttributes(ca1=new ColoringAttributes()); ca1.setColor(fr,fg,fb);
//lined (wire) shape:
addChild(s2=new Shape3D(geo, ap2=new Appearance()));
ap2.setPolygonAttributes(pa2=new PolygonAttributes()); pa2.setPolygonMode(pa2.POLYGON_LINE);
ap2.setColoringAttributes(ca2=new ColoringAttributes()); ca2.setColor(br,bg,bb);
pa2.setPolygonOffset(-1000); //Uncertain what "float" value to use!
class CubeGeometry extends IndexedQuadArray //cube geometry data
private static final int[] faces =
0,3,2,1,
0,1,5,4,
1,2,6,5,
2,3,7,6,
3,0,4,7,
4,5,6,7
private static float[] verts = new float[24];
public CubeGeometry(float ax, float ay, float az, //lower limit
float bx, float by, float bz) //upper limit
super(8, IndexedQuadArray.COORDINATES , 24);
int n;
n=0; verts[n]=ax; verts[n+1]=ay; verts[n+2]=az;
n=3; verts[n]=bx; verts[n+1]=ay; verts[n+2]=az;
n=6; verts[n]=bx; verts[n+1]=by; verts[n+2]=az;
n=9; verts[n]=ax; verts[n+1]=by; verts[n+2]=az;
n=12; verts[n]=ax; verts[n+1]=ay; verts[n+2]=bz;
n=15; verts[n]=bx; verts[n+1]=ay; verts[n+2]=bz;
n=18; verts[n]=bx; verts[n+1]=by; verts[n+2]=bz;
n=21; verts[n]=ax; verts[n+1]=by; verts[n+2]=bz;
setCoordinates(0, verts);
setCoordinateIndices(0, faces);