问题
Using java3d, how can I colorize not on a per vertex base but on a per face base?
I try to learn about java3d but what Shape3d I did produce does not look as expected. I want to colorize different triangles in different colors, but I don't see how to do it.
Texture looks like an overkill, and what's more, I haven't mastered this part at all. As far as I've seen Materials work on a complete GeometryArray, so are no good here. Per vertex colors won't do the trick.
回答1:
I fond the solution. "per vertex colors" really are per vertex reference, so each vertex can have a different color for each of its faces.
Here is a working example (regrettably not very small):
package examples;
import javax.media.j3d.Alpha;
import javax.media.j3d.AmbientLight;
import javax.media.j3d.Appearance;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.Bounds;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.DirectionalLight;
import javax.media.j3d.GeometryArray;
import javax.media.j3d.IndexedTriangleArray;
import javax.media.j3d.Node;
import javax.media.j3d.PolygonAttributes;
import javax.media.j3d.RotationInterpolator;
import javax.media.j3d.Shape3D;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.media.j3d.View;
import javax.media.j3d.ViewPlatform;
import javax.vecmath.Color3f;
import javax.vecmath.Point3d;
import javax.vecmath.Vector3f;
import com.sun.j3d.utils.geometry.GeometryInfo;
import com.sun.j3d.utils.geometry.NormalGenerator;
import com.sun.j3d.utils.universe.MultiTransformGroup;
import com.sun.j3d.utils.universe.SimpleUniverse;
import com.sun.j3d.utils.universe.ViewingPlatform;
public class Example {
public static void main(final String[] args) {
new Example();
}
public Example() {
final SimpleUniverse universe = new SimpleUniverse();
final BranchGroup group = new BranchGroup();
final TransformGroup tg = new TransformGroup();
final BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 100.0);
final Node blob = createMonster();
{ //to enable rotation
tg.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
tg.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
}
// Create rotation to see all sides of the object
final Transform3D btrans = new Transform3D();
btrans.rotX(1);
final Transform3D ztrans = new Transform3D();
ztrans.rotZ(-1);
btrans.mul(ztrans);
final RotationInterpolator ri = createRotation(tg, bounds, btrans, 7000);
tg.addChild(ri);
tg.addChild(blob);
//
group.addChild(tg);
//
addLight(group, new Color3f(1f, 1f, 0f), new Vector3f(4.0f, +7.0f, -12.0f));
addLight(group, new Color3f(1f, 1f, 1f));
//
final ViewingPlatform viewingPlatform = universe.getViewingPlatform();
final ViewPlatform view = viewingPlatform.getViewPlatform();
view.setViewAttachPolicy(View.NOMINAL_SCREEN);
viewingPlatform.setNominalViewingTransform();
final MultiTransformGroup mtg = viewingPlatform.getMultiTransformGroup();
final TransformGroup vtg = mtg.getTransformGroup(0);
final Transform3D t1 = btrans;
vtg.getTransform(t1);
t1.setScale(2);
vtg.setTransform(t1);
group.compile();
// add the group of objects to the Universe
universe.addBranchGraph(group);
}
private Node createMonster() {
final Shape3D child = createShape();
final Appearance fillAppNode = new Appearance();
final PolygonAttributes pAtt = new PolygonAttributes();
// avoid trouble with clockwise faces
pAtt.setCullFace(PolygonAttributes.CULL_NONE);
pAtt.setBackFaceNormalFlip(true);
fillAppNode.setPolygonAttributes(pAtt);
child.setAppearance(fillAppNode);
return child;
}
private Shape3D createShape() {
final Point3d[] points = new Point3d[] {//
new Point3d(-1, 1, 0), //
new Point3d(1, 1, 0), //
new Point3d(1, -1, 0), //
new Point3d(-1, -1, 0), //
new Point3d(0, 0, 1), //
};
final int[] idxs = new int[] {// the triangle faces
0, 1, 2,//
2, 3, 0,//
1, 0, 4,//
1, 2, 4,//
2, 3, 4,//
3, 0, 4 };
final IndexedTriangleArray ita = new IndexedTriangleArray(points.length, GeometryArray.COORDINATES
| GeometryArray.COLOR_3, idxs.length);
ita.setCoordinates(0, points);
ita.setCoordinateIndices(0, idxs);
//per vertex colors really are per vertex reference
//so each vertex can have a different color for each of its faces
final Color3f[] colors = new Color3f[] {//
new Color3f(1, 0, 1),//
new Color3f(0, 1, 0),//
new Color3f(0, 0, 1),//
new Color3f(1, 1, 0),//
new Color3f(1, 1, 1),//
};
ita.setColors(0, colors);
ita.setColorIndices(0, idxs);
ita.setColorIndices(0, new int[] { 0, 0, 0, 1, 1, 1 });
//
final GeometryInfo gi = new GeometryInfo(ita);
//also generate normal vectors so that the surface can be light
final NormalGenerator normalGenerator = new NormalGenerator();
normalGenerator.generateNormals(gi);
final GeometryArray geometryArray = gi.getGeometryArray();
return new Shape3D(geometryArray);
}
private RotationInterpolator createRotation(final TransformGroup objScale, final Bounds bounds,
final Transform3D btrans, final long milis) {
final Alpha alpha = new Alpha(-1, Alpha.INCREASING_ENABLE, 0, 0, milis, 0, 0, 0, 0, 0);
final RotationInterpolator ri = new RotationInterpolator(alpha, objScale, btrans, 0.0f, (float) Math.PI * 2.0f);
ri.setSchedulingBounds(bounds);
return ri;
}
private void addLight(final BranchGroup group, final Color3f light1Color, final Vector3f ligthDirection) {
{
final BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 100.0);
final DirectionalLight light1 = new DirectionalLight(light1Color, ligthDirection);
light1.setInfluencingBounds(bounds);
group.addChild(light1);
}
}
private void addLight(final BranchGroup group, final Color3f light1Color) {
{
final BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 100.0);
final AmbientLight light1 = new AmbientLight(light1Color);
light1.setInfluencingBounds(bounds);
group.addChild(light1);
}
}
}
回答2:
You will have to draw each face separately, assigning a color to each. For example:
Appearance polygon1Appearance = new Appearance();
// set your color here
QuadArray polygon1 = new QuadArray (4, QuadArray.COORDINATES);
polygon1.setCoordinate(0, new Point3f (0f, 0f, 0f));
polygon1.setCoordinate(1, new Point3f (2f, 0f, 0f));
polygon1.setCoordinate(2, new Point3f (2f, 3f, 0f));
polygon1.setCoordinate(3, new Point3f (0f, 3f, 0f));
objRoot.addChild(new Shape3D(polygon1, polygon1Appearance));
来源：https://stackoverflow.com/questions/26369331/face-coloring-in-java3d