简单的透明度示例不适用于Java 3D

Question

我是j3d中的完整n00b(但是Java专家).刚刚开始,我遇到了一个透明度问题.我有一个简单的例子,绘制一个旋转的平面四边形(显示背面消失,因为我没有禁用背面剔除).

将Color3b和COLOR_3线取消注释(以及相应的Color4b和COLOR_4线注释),我看到旋转的四边形,红色.

但是,当我评论color-3线并取消注释color-4线时,我看到一个黑色正方形(相对于白色背景),即使alpha值设置为255(完全不透明).

我究竟做错了什么？谷歌没有帮助,甚至java.forums.net上的Java3D论坛都没有帮助.StackOverflow,救救我!您可以复制并通过以下程序,运行它,看看会发生什么.

这是我的规格:

OSX 10.5.5上的Java 6 J3D 1.5.2 JOGL 1.1.1

谢谢,

- 抢

这是代码:

import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.geometry.ColorCube;
import com.sun.j3d.utils.universe.SimpleUniverse;
import java.applet.Applet;
import java.awt.*;
import javax.media.j3d.*;
import javax.vecmath.*;

public class Hello extends Applet
{
 public Hello() throws Exception
 {
  setLayout(new BorderLayout());
  GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration();
  Canvas3D canvas3D = new Canvas3D(config);

  add("Center", canvas3D);

  BranchGroup scene = createSceneGraph();
  scene.compile();

  SimpleUniverse univ = new SimpleUniverse(canvas3D);

  univ.getViewingPlatform().setNominalViewingTransform();

  univ.addBranchGraph(scene);
 }

 public BranchGroup createSceneGraph() throws Exception
 {
  BranchGroup root = new BranchGroup();

  // A white background.

  Background bgd = new Background(1.0f, 1.0f, 1.0f);
  root.addChild(bgd);

  // This will spin the quad around

  TransformGroup spin = new TransformGroup();
  spin.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
  root.addChild(spin);

  // define the quad:

  Point3d p1 = new Point3d(-0.5, -0.5, 0);
  Point3d p2 = new Point3d(0.5, -0.5, 0);
  Point3d p3 = new Point3d(0.5, 0.5, 0);
  Point3d p4 = new Point3d(-0.5, 0.5, 0);

  // colors

  Color4b c = new Color4b((byte)255, (byte)0, (byte)0, (byte)255);
  //Color3b c = new Color3b((byte)255, (byte)0, (byte)0);

  QuadArray quads = new QuadArray(4,
    GeometryArray.COORDINATES | GeometryArray.COLOR_4);
    // GeometryArray.COORDINATES | GeometryArray.COLOR_3);

  quads.setCoordinate(0, p1);
  quads.setCoordinate(1, p2);
  quads.setCoordinate(2, p3);
  quads.setCoordinate(3, p4);
  quads.setColor(0, c);
  quads.setColor(1, c);
  quads.setColor(2, c);
  quads.setColor(3, c);

  // Not sure if I need this. Doesn't seem to make a difference.

  Appearance appearance = new Appearance();
  TransparencyAttributes trans = new TransparencyAttributes();
  trans.setTransparencyMode(TransparencyAttributes.BLENDED);
  appearance.setTransparencyAttributes(trans);

  // Create the shape...

  Shape3D shape = new Shape3D();
  shape.setGeometry(quads);
  shape.setAppearance(appearance);

  spin.addChild(shape);

  Alpha rotationAlpha = new Alpha(-1, 4000);
  RotationInterpolator rotator = new RotationInterpolator(rotationAlpha, spin);
  BoundingSphere bounds = new BoundingSphere();
  rotator.setSchedulingBounds(bounds);
  spin.addChild(rotator);

  return root;
 }

 public static void main(String[] args) throws Exception
 {
  Frame frame = new MainFrame(new Hello(), 256, 256);
 }
} 

Answer 1

用 Color4f 替换 Color4b 对我有用。将代码中的相应行替换为以下行，

Color color = new Color(255, 0, 0, 50);

Color4f c = new Color4f(color);
QuadArray quads = new QuadArray(4, 
           GeometryArray.COORDINATES | GeometryArray.COLOR_4);

我使用 AWT Color，发现更容易传递所有 ColorNx() 构造函数，即 Color3b()、Color4b() 和 Color4f() 等。如果您觉得自然，您可以直接使用浮点参数。实际的修复是使用 Color4f，而不是 AWT。即使使用 AWT Color 也无法解决 Color4b 的问题。就用Color4f吧，我没有发现任何问题。

我的平台： Java 版本“1.6.0_10”、Java 3D 1.5.2、Core2 Duo、OpenSUSE 11.0、Intel G33 Graphics。