我正在尝试让一个物体在正方形中飞过我的场景(它做得正确),但我希望它也面向它要去的地方......
目前的问题是物体在飞行,并且在飞行时它会旋转(这是不自然的)。我希望它飞到一点,然后停下来旋转,然后飞到下一个点,然后再次旋转,依此类推。
我正在尝试使用 Java3D 函数来实现这一点: RotPosPathInterpolator
这就是我正在做的事情:
Alpha alphaNave = new Alpha( -1, Alpha.INCREASING_ENABLE, 0,0,6000,0,0,0,0,0 );
TransformGroup target = new TransformGroup();
Transform3D axisOfRotPos = new Transform3D();
float[] alphas = {0.0f, 0.25f, 0.50f, 0.75f, 1.0f};
Quat4f[] quats = new Quat4f[5];
Point3f[] positions = new Point3f[5];
target.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
quats[0] = new Quat4f(0.0f, 1.0f, 0.0f, (float) Math.toRadians(0));
quats[1] = new Quat4f(0.0f, 1.0f, 0.0f, (float) Math.toRadians(90));
quats[2] = new Quat4f(0.0f, 1.0f, 0.0f, (float) Math.toRadians(180));
quats[3] = new Quat4f(0.0f, 1.0f, 0.0f, (float) Math.toRadians(270));
quats[4] = quats[0];
positions[0]= new Point3f( -20.0f, 0.0f, 20.0f);
positions[1]= new Point3f( -20.0f, 0.0f, -20.0f);
positions[2]= new Point3f( 20.0f, 0.0f, -20.0f);
positions[3]= new Point3f( 20.0f, 0.0f, 20.0f);
positions[4]= positions[0];
RotPosPathInterpolator rotPosPath = new RotPosPathInterpolator(
alphaNave, target, axisOfRotPos, alphas, quats, positions);
最佳答案
首先是一个简短的旁注:创建四元数时,最后一个分量不仅仅是角度。为了创建一个描述围绕某个轴、某个角度旋转的四元数,最简单的方法是遍历 AxisAngle4f 类。
AxisAngle4f a = new AxisAngle4f(0.0f, 1.0f, 0.0f, angleInRadians);
Quat4f q = new Quat4f();
q.set(a);
(不幸的是,没有方便的构造函数。我建议将这 3 行代码包装在返回适当四元数的实用程序方法中)。
<小时/>关于实际问题:如果我理解正确的话,期望的行为是这样的:
(这是根据我在下面添加的 MCVE 创建的)。
如果您只想进行移动(不旋转),则必须在插值路径中插入两个点,其中仅位置发生变化,但旋转保持不变。同样,当您只需要旋转时,您必须创建两个点,其中仅旋转发生变化,但位置保持不变。当然,您始终必须相应地调整您的 alpha
值。
在此示例中,您的路径将由 9 个点组成。手动添加这些点并计算所需的 alpha 值很麻烦。我建议为此创建一个小型实用程序类。以下 MCVE 允许将点(每个点由一个位置和一个角度组成)添加到 InterpolatorData 类,该类随后为插值器提供数据。
import java.awt.GraphicsConfiguration;
import java.util.ArrayList;
import java.util.List;
import javax.media.j3d.Alpha;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.RotPosPathInterpolator;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.vecmath.AxisAngle4f;
import javax.vecmath.Point3d;
import javax.vecmath.Point3f;
import javax.vecmath.Quat4f;
import javax.vecmath.Vector3d;
import com.sun.j3d.utils.geometry.ColorCube;
import com.sun.j3d.utils.universe.SimpleUniverse;
public class RotPosPathInterpolatorTest
{
public static void main(String[] args)
{
System.setProperty("sun.awt.noerasebackground", "true");
SwingUtilities.invokeLater(new Runnable()
{
@Override
public void run()
{
createAndShowGUI();
}
});
}
private static void createAndShowGUI()
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);;
GraphicsConfiguration config =
SimpleUniverse.getPreferredConfiguration();
Canvas3D canvas = new Canvas3D(config);
frame.getContentPane().add(canvas);
SimpleUniverse simpleUniverse = new SimpleUniverse(canvas);
BranchGroup rootBranchGroup = new BranchGroup();
createContents(rootBranchGroup);
simpleUniverse.addBranchGraph(rootBranchGroup);
Transform3D t0 = new Transform3D();
t0.rotX(Math.toRadians(-45));
Transform3D t1 = new Transform3D();
t1.setTranslation(new Vector3d(0,0,10));
t0.mul(t1);
simpleUniverse.
getViewingPlatform().
getViewPlatformTransform().
setTransform(t0);
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private static class InterpolatorData
{
private final List<Point3f> positions = new ArrayList<Point3f>();
private final List<Quat4f> orientations = new ArrayList<Quat4f>();
void add(Point3f p, float angleDeg)
{
positions.add(p);
AxisAngle4f a = new AxisAngle4f(
0.0f, 1.0f, 0.0f, (float) Math.toRadians(angleDeg));
Quat4f q = new Quat4f();
q.set(a);
orientations.add(q);
}
Point3f[] getPositions()
{
return positions.toArray(new Point3f[0]);
}
Quat4f[] getOrientations()
{
return orientations.toArray(new Quat4f[0]);
}
float[] getAlphas()
{
float alphas[] = new float[positions.size()];
float delta = 1.0f / (alphas.length - 1);
for (int i=0; i<alphas.length; i++)
{
alphas[i] = i * delta;
}
return alphas;
}
}
private static void createContents(BranchGroup rootBranchGroup)
{
Alpha alpha = new Alpha(-1, Alpha.INCREASING_ENABLE,
0, 0, 6000, 0, 0, 0, 0, 0);
TransformGroup target = new TransformGroup();
target.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
Transform3D axisOfTransform = new Transform3D();
InterpolatorData i = new InterpolatorData();
i.add(new Point3f(-2.0f, 0.0f, 2.0f), 0.0f);
i.add(new Point3f(-2.0f, 0.0f, -2.0f), 0.0f);
i.add(new Point3f(-2.0f, 0.0f, -2.0f), 90.0f);
i.add(new Point3f( 2.0f, 0.0f, -2.0f), 90.0f);
i.add(new Point3f( 2.0f, 0.0f, -2.0f), 180.0f);
i.add(new Point3f( 2.0f, 0.0f, 2.0f), 180.0f);
i.add(new Point3f( 2.0f, 0.0f, 2.0f), 270.0f);
i.add(new Point3f(-2.0f, 0.0f, 2.0f), 270.0f);
i.add(new Point3f(-2.0f, 0.0f, 2.0f), 0.0f);
RotPosPathInterpolator interpolator = new RotPosPathInterpolator(
alpha, target, axisOfTransform,
i.getAlphas(), i.getOrientations(), i.getPositions());
interpolator.setSchedulingBounds(
new BoundingSphere(new Point3d(), 100.0));
rootBranchGroup.addChild(target);
target.addChild(interpolator);
target.addChild(new ColorCube(0.4));
}
}
<小时/>
另一条评论:使用这样的实用程序类,此解决方案可能没问题,但对于更复杂的路径和行为,可能会为路径处理创建专用的基础设施。
关于java - 使用 java3D 和 rotpospathInterpolator 制作正确的动画,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29609439/