Java3d offsecreen渲染与屏幕不同

Question

我有java3d的以下程序。我使用的是http://jogamp.org/wiki/index.php/Downloading_and_installing_Java3D

的最新版本

当我渲染显示（justDisplay = true）时，它看起来像那样

Whan我渲染到文件（justDisplay = false）它看起来像

渲染到文件时，为什么侧面不是蓝色？

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.media.j3d.Appearance;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.ColoringAttributes;
import javax.media.j3d.DirectionalLight;
import javax.media.j3d.ImageComponent;
import javax.media.j3d.ImageComponent2D;
import javax.media.j3d.LineArray;
import javax.media.j3d.Material;
import javax.media.j3d.PointLight;
import javax.media.j3d.Screen3D;
import javax.media.j3d.ShaderAppearance;
import javax.media.j3d.Shape3D;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.swing.JFrame;
import javax.vecmath.Color3f;
import javax.vecmath.Point3d;
import javax.vecmath.Point3f;
import javax.vecmath.Vector3f;

import com.sun.j3d.utils.geometry.Box;
import com.sun.j3d.utils.universe.SimpleUniverse;

public class HelloJava3Db {

    public static void main(String[] args) {

        boolean justDisplay = true;

        // create canvas
        GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration();
        Canvas3D canvas3D = new Canvas3D(config, !justDisplay);

        if (justDisplay) {
            JFrame jFrame = new JFrame("huhu");
            jFrame.setVisible(true);
            jFrame.setSize(1000, 1000);
            jFrame.add(canvas3D);
        }

        // create universe
        SimpleUniverse simpleU = new SimpleUniverse(canvas3D);
        simpleU.getViewingPlatform().setNominalViewingTransform();

        // create scene
        BranchGroup scene = new BranchGroup();

        Transform3D drehungX = new Transform3D();
        Transform3D drehungY = new Transform3D();
        drehungX.rotX(Math.toRadians(30));
        drehungY.rotY(Math.toRadians(20));
        drehungX.mul(drehungY);
        TransformGroup objDreh = new TransformGroup(drehungX);

        Appearance a = new ShaderAppearance();
        Material material = new Material(new Color3f(Color.BLUE), new Color3f(Color.RED), new Color3f(Color.YELLOW), new Color3f(Color.GREEN), 10f);
        material.setLightingEnable(true);
        material.setEmissiveColor(0, 0, 0);
        a.setMaterial(material);
        Box upperBox = new Box(0.1f, 0.1f, 0.1f, a);
        objDreh.addChild(upperBox);
        scene.addChild(objDreh);

        Transform3D unten = new Transform3D();
        unten.setTranslation(new Vector3f(0, -0.5f, 0));
        TransformGroup untenGroup = new TransformGroup(unten);
        untenGroup.addChild(new Box(0.5f, 0.01f, 0.5f, a));
        scene.addChild(untenGroup);

        PointLight pl = new PointLight(new Color3f(Color.WHITE), new Point3f(0, 0.5f, 0), new Point3f(0.0f, 0.0f, 0.2f));
        pl.setInfluencingBounds(new BoundingSphere());
        scene.addChild(pl);

        Color3f light1Color = new Color3f(1.0f, 0.0f, 0.0f);
        BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 100000.0);
        Vector3f light1Direction = new Vector3f(0.0f, -1.0f, 0.0f);
        DirectionalLight light1 = new DirectionalLight(light1Color, light1Direction);
        light1.setInfluencingBounds(bounds);
        // scene.addChild(light1);

        // AXIS
        // X
        LineArray lineX = new LineArray(2, LineArray.COORDINATES);
        lineX.setCoordinate(0, new Point3f(-1000.0f, 0.0f, 0.0f));
        lineX.setCoordinate(1, new Point3f(1000.0f, 0.0f, 0.0f));
        Appearance appearanceGreen = new Appearance();
        ColoringAttributes coloringAttributesGreen = new ColoringAttributes();
        coloringAttributesGreen.setColor(new Color3f(Color.green));
        appearanceGreen.setColoringAttributes(coloringAttributesGreen);
        Shape3D shapeLine = new Shape3D(lineX, appearanceGreen);
        scene.addChild(shapeLine);

        // Y
        LineArray lineY = new LineArray(2, LineArray.COORDINATES);
        lineY.setCoordinate(0, new Point3f(0.0f, -1000.0f, 0.0f));
        lineY.setCoordinate(1, new Point3f(0.0f, 1000.0f, 0.0f));
        scene.addChild(new Shape3D(lineY));

        // Z
        LineArray lineZ = new LineArray(2, LineArray.COORDINATES);
        lineZ.setCoordinate(0, new Point3f(0.0f, 0.0f, -1000.0f));
        lineZ.setCoordinate(1, new Point3f(0.0f, 0.0f, 1000.0f));
        scene.addChild(new Shape3D(lineZ));

        scene.compile();
        simpleU.addBranchGraph(scene);

        if (!justDisplay) {
            // set off screen size
            Screen3D sOff = canvas3D.getScreen3D();
            sOff.setSize(new Dimension(1000, 1000));
            sOff.setPhysicalScreenWidth(3);
            sOff.setPhysicalScreenHeight(3);

            // render to off screen
            BufferedImage bImage = new BufferedImage(1000, 1000, BufferedImage.TYPE_INT_ARGB);
            ImageComponent2D buffer = new ImageComponent2D(ImageComponent.FORMAT_RGBA, bImage);
            buffer.setCapability(ImageComponent2D.ALLOW_IMAGE_READ);
            canvas3D.setOffScreenBuffer(buffer);
            canvas3D.renderOffScreenBuffer();
            canvas3D.waitForOffScreenRendering();

            // write to file
            File output = new File("img.png");
            try {
                ImageIO.write(canvas3D.getOffScreenBuffer().getRenderedImage(), "png", output);
            } catch (IOException e) {
                e.printStackTrace();
            }
            System.out.println(output.getAbsolutePath());
        }
        // System.exit(0);
    }

}