- 前言
- 坐标对应关系
- 加一个面
鉴于许多同学对计算机图形学设计作品无法下手，特此推出Java3D设计作品入门级教程，可以给予毫无头绪的你一点思路。本文仅起到抛砖引玉的作用，并不提供现成的作品。
坐标对应关系首先我们要理解java3d中的坐标轴，这个坐标轴与我们平常摆的位置的不太一样，所以要做下区分
然后我们把这个坐标轴代入到我们真实的环境中，代码及运行结果如下：
package com.test.demo01;
import java.applet.Applet;
import java.awt.*;
import com.sun.j3d.utils.applet.Mainframe;
import com.sun.j3d.utils.geometry.*;
import com.sun.j3d.utils.universe.*;
import javax.media.j3d.*;
import javax.vecmath.*;
import com.sun.j3d.utils.behaviors.mouse.*;
public class BezierSurfaceMerging extends Applet
{public BranchGroup createBranchGroupSceneGraph()
{BranchGroup BranchGroupRoot =new BranchGroup();
BoundingSphere bounds=new BoundingSphere(new Point3d(0.0,0.0,0.0),100.0);
Color3f bgColor=new Color3f(0f,1.0f,1.0f);
Background bg=new Background(bgColor);
bg.setApplicationBounds(bounds);
BranchGroupRoot.addChild(bg);
Color3f directionalColor=new Color3f(1.f,0.f,0.f);
Vector3f vec=new Vector3f(0.f,0.f,-1.0f);
DirectionalLight directionalLight=new DirectionalLight(directionalColor,vec);
directionalLight.setInfluencingBounds(bounds);
BranchGroupRoot.addChild(directionalLight);
Transform3D tr=new Transform3D();
tr.setScale(0.85);
TransformGroup transformgroup=new TransformGroup(tr);
transformgroup.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
transformgroup.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
BranchGroupRoot.addChild(transformgroup);
MouseRotate mouserotate = new MouseRotate();
mouserotate.setTransformGroup(transformgroup);
BranchGroupRoot.addChild(mouserotate);
mouserotate.setSchedulingBounds(bounds);
MouseZoom mousezoom = new MouseZoom();
mousezoom.setTransformGroup(transformgroup);
BranchGroupRoot.addChild(mousezoom);
mousezoom.setSchedulingBounds(bounds);
MouseTranslate mousetranslate = new MouseTranslate();
mousetranslate.setTransformGroup(transformgroup);
BranchGroupRoot.addChild(mousetranslate);
mousetranslate.setSchedulingBounds(bounds);
//定义第一个Bezier曲面的16个控制顶点
float[][][] P1={{{-0.8f,0.9f,-0.4f,1.f},
{-0.2f,0.8f,-0.5f,1.f},
{0.2f,0.9f,-0.4f,1.f},
{0.8f,0.8f,-0.5f,1.f} },
{ {-0.8f,0.7f,-0.4f,1.f},
{-0.2f,0.6f,0.9f,1.f},
{0.2f,0.7f,0.8f,1.f},
{0.8f,0.6f,-0.4f,1.f} },
{{-0.8f,0.4f,-0.4f,1.f},
{-0.2f,0.5f,0.8f,1.f},
{0.2f,0.3f,0.7f,1.f},
{0.8f,0.4f,-0.5f,1.f} },
{ {-0.8f,0.f,-0.8f,1.f},
{-0.2f,0.1f,0.9f,1.f},
{0.2f,0.f,-0.8f,1.f},
{0.8f,0.1f,0.9f,1.f} } };
//定义第一个Bezier曲面外观属性
Appearance app1 = new Appearance();
PolygonAttributes polygona1=new PolygonAttributes();
polygona1.setBackFaceNormalFlip(true);
polygona1.setCullFace(PolygonAttributes.CULL_NONE);
// polygona1.setPolygonMode(PolygonAttributes.POLYGON_LINE);
app1.setPolygonAttributes(polygona1);
ColoringAttributes color1=new ColoringAttributes();
color1.setColor(1.f,0.f,0.f);
app1.setColoringAttributes(color1);
Shape3D BezierSurfaceface1=new BezierThreeOrderSurfaceface(P1,app1);
transformgroup.addChild(BezierSurfaceface1);
BranchGroupRoot.compile();
return BranchGroupRoot;
}
public BezierSurfaceMerging()
{setLayout(new BorderLayout());
GraphicsConfiguration gc = SimpleUniverse.getPreferredConfiguration();
Canvas3D c=new Canvas3D(gc);
add("Center",c);
BranchGroup BranchGroupScene=createBranchGroupSceneGraph();
SimpleUniverse u=new SimpleUniverse(c);
u.getViewingPlatform().setNominalViewingTransform();
u.addBranchGraph(BranchGroupScene);
}
public static void main(String[] args)
{new Mainframe(new BezierSurfaceMerging(),400,400); }
}
class BezierThreeOrderSurfaceface extends Shape3D
{public BezierThreeOrderSurfaceface(float[][][] P,Appearance app)
{int i,j,k;
int n0;//定义对参数u、v在[0，1]区间的等分点数
float division;//参数u在[0，1]区间的等分线段长度
n0=50;division=1.f/n0;
//分别定义存放控制顶点x、y、z坐标与第四维坐标的数组
float[][] PX=new float[4][4];
float[][] PY=new float[4][4];
float[][] PZ=new float[4][4];
float[][] P4=new float[4][4];
//定义系数矩阵及其转置矩阵
float[][] M1={{1.f,0.f,0.f,0.f},
{-3.f,3.f,0.f,0.f},
{3.f,-6.f,3.f,0.f},
{-1.f,3.f,-3.f,1.f}};
float[][] M2={{1.f,-3.f,3.f,-1.f},
{0.f,3.f,-6.f,3.f},
{0.f,0.f,3.f,-3.f},
{0.f,0.f,0.f,1.f}};
//定义Bezier曲面的u、v参数分割点坐标数组
float[][][] UV=new float[n0+1][n0+1][2];
//定义U、V矩阵数组
float[][] UU=new float[1][4];
float[][] VV=new float[4][1];
//定义存放曲面上点的坐标的数组
float[][][] SurfaceXYZ=new float[n0+1][n0+1][4];
for(i=0;i
在这一长段代码中，只有P1的这16个坐标是我们要改动的地方，这16个的坐标共同组成了一个曲面。每个点包含了4个坐标，但其中的1.f我们是不需要去动的，因此真正有用的是前三个
{X, Y, Z, 1.f}
这里的XYZ就分别对应到上述提到的坐标轴中，那么理解了坐标是怎么使用后，还要将坐标对应到曲面中。
为了方便演示，我们将P1中的坐标改成如下：
float[][][] P1={
{{-0.8f, -1.2f, -0.8f, 1.f}, {-0.2f, 0.2f, -0.5f, 1.f},
{0.2f, 0.3f, -0.5f, 1.f}, {0.8f, -1.2f, -0.8f, 1.f}},
{{-0.8f, -0.1f, -0.2f, 1.f}, {-0.2f, 0.9f, -0.2f, 1.f},
{0.2f, 0.9f, -0.2f, 1.f}, {0.8f, -0.1f, -0.2f, 1.f}},
{{-0.8f, -0.1f, 0.2f, 1.f}, {-0.2f, 0.9f, 0.2f, 1.f},
{0.2f, 0.9f, 0.2f, 1.f}, {0.8f, -0.1f, 0.2f, 1.f}},
{{-0.6f, -0.6f, 0.9f, 1.f}, {-0.2f, 0.2f, 0.5f, 1.f},
{0.2f, 0.3f, 0.5f, 1.f}, {0.6f, -0.65f, 0.8f, 1.f}}};
运行我们的代码，得到如下结果：
到这步后，我们要把最前面提到的坐标轴，与这张图相结合。这里注意一下，为了避免把自己搞混乱，运行出结果后就不要随便去转动它！！！第一印象很重要。
这就是在这张图中代表的坐标系（上下位置不一定准确）
我们的重头戏要来了，这16个点分别代表图中的哪个位置，因为这个图像凹凸有致，我们很容易想到去调整它的Y坐标，来得到最佳的观察效果。
我们将这里的坐标分别4组，从上至下，从左至右，依次记为1，2，3……16
首先我们将第一个点的Y坐标改为0，观察效果
可以看到已经有了一定的变化，随后我们转动图像，以俯视的视角，也就是想象自己飞到了图像的上方。
可以看到图形的这一角比较特别，相比较原先有点翘起，归根结底就是我们把第一个点的纵坐标由-1.2f变为了0f，产生了这个效果。有兴趣的同学可以再把它改成-1.2f，就会得到如下 结果：
我们依葫芦画瓢，把这16个点都改一遍，也就是只把它们的Y坐标改为0，分别会得到以下结果（均采用了俯视的视角）：
到这里，我们第一组的坐标全部测试完毕了，相信大家一定对坐标和曲面之间的对应关系有了一定的了解。现在我们再测一下每组的第一个点，同样修改其Y坐标
自己都试一遍印象才能深刻噢！
接着我们看看把全部的Y坐标归0的结果
可以看到打开的时候已经变成了一个平面了，不再是曲面，这也给了 我们一个构造平面的思路，也就是把16个的坐标的XYZ任意一个全部设置为0，就可以得到平面。
当然学到这里，你已经掌握了一个曲面是如何运转的，然而我们的作品肯定不是只由一个曲面就能完成，除非你看开了。
加一个面
接下来我们将详细分析一下，自己如何再加一个曲面
添加如下代码， 这里的P2是由P1的Y坐标修改为0.5f得来，也就是把整个面往上抬了0.5f的距离，可以先在脑海中想想会是什么样子再往下滑，建立空间感
float[][][] P2={
{{-0.8f, 0.5f, -0.8f, 1.f}, {-0.2f, 0.5f, -0.5f, 1.f},
{0.2f, 0.5f, -0.5f, 1.f}, {0.8f, 0.5f, -0.8f, 1.f}},
{{-0.8f, 0.5f, -0.2f, 1.f}, {-0.2f, 0.5f, -0.2f, 1.f},
{0.2f, 0.5f, -0.2f, 1.f}, {0.8f, 0.5f, -0.2f, 1.f}},
{{-0.8f, 0.5f, 0.2f, 1.f}, {-0.2f, 0.5f, 0.2f, 1.f},
{0.2f, 0.5f, 0.2f, 1.f}, {0.8f, 0.5f, 0.2f, 1.f}},
{{-0.6f, 0.5f, 0.9f, 1.f}, {-0.2f, 0.5f, 0.5f, 1.f},
{0.2f, 0.5f, 0.5f, 1.f}, {0.6f, 0.5f, 0.8f, 1.f}}};
//定义第一个Bezier曲面外观属性
Appearance app2 = new Appearance();
PolygonAttributes polygona2=new PolygonAttributes();
polygona2.setBackFaceNormalFlip(true);
polygona2.setCullFace(PolygonAttributes.CULL_NONE);
polygona2.setPolygonMode(PolygonAttributes.POLYGON_LINE);
app2.setPolygonAttributes(polygona2);
ColoringAttributes color2=new ColoringAttributes();
color2.setColor(0.8f,0.f,0.f);
app2.setColoringAttributes(color2);
Shape3D BezierSurfaceface2=new BezierThreeOrderSurfaceface(P2,app2);
transformgroup.addChild(BezierSurfaceface2);
说说要改的地方，P2 app2 polygona2 color2 BezierSurfaceface2
这里都由原先的1改为了2，要是想添加3个，4个，10个，100个，也是以此类推。
效果如下：
看到这里，相信你一定已经会意了
小练习：可以先动手试试如何用6个曲面拼成一个方块
本次教程就到这里了，快去完成自己的设计作品吧！
4班冲！
package com.test.demo01;
import java.applet.Applet;
import java.awt.*;
import com.sun.j3d.utils.applet.Mainframe;
import com.sun.j3d.utils.geometry.*;
import com.sun.j3d.utils.universe.*;
import javax.media.j3d.*;
import javax.vecmath.*;
import com.sun.j3d.utils.behaviors.mouse.*;
public class BezierSurfaceMerging extends Applet
{public BranchGroup createBranchGroupSceneGraph()
{BranchGroup BranchGroupRoot =new BranchGroup();
BoundingSphere bounds=new BoundingSphere(new Point3d(0.0,0.0,0.0),100.0);
Color3f bgColor=new Color3f(0f,1.0f,1.0f);
Background bg=new Background(bgColor);
bg.setApplicationBounds(bounds);
BranchGroupRoot.addChild(bg);
Color3f directionalColor=new Color3f(1.f,0.f,0.f);
Vector3f vec=new Vector3f(0.f,0.f,-1.0f);
DirectionalLight directionalLight=new DirectionalLight(directionalColor,vec);
directionalLight.setInfluencingBounds(bounds);
BranchGroupRoot.addChild(directionalLight);
Transform3D tr=new Transform3D();
tr.setScale(0.85);
TransformGroup transformgroup=new TransformGroup(tr);
transformgroup.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
transformgroup.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
BranchGroupRoot.addChild(transformgroup);
MouseRotate mouserotate = new MouseRotate();
mouserotate.setTransformGroup(transformgroup);
BranchGroupRoot.addChild(mouserotate);
mouserotate.setSchedulingBounds(bounds);
MouseZoom mousezoom = new MouseZoom();
mousezoom.setTransformGroup(transformgroup);
BranchGroupRoot.addChild(mousezoom);
mousezoom.setSchedulingBounds(bounds);
MouseTranslate mousetranslate = new MouseTranslate();
mousetranslate.setTransformGroup(transformgroup);
BranchGroupRoot.addChild(mousetranslate);
mousetranslate.setSchedulingBounds(bounds);
//定义第一个Bezier曲面的16个控制顶点
float[][][] P1={
{{-0.8f, 0f, -0.8f, 1.f}, {-0.2f, 0f, -0.5f, 1.f},
{0.2f, 0f, -0.5f, 1.f}, {0.8f, 0f, -0.8f, 1.f}},
{{-0.8f, 0f, -0.2f, 1.f}, {-0.2f, 0f, -0.2f, 1.f},
{0.2f, 0f, -0.2f, 1.f}, {0.8f, 0f, -0.2f, 1.f}},
{{-0.8f, 0f, 0.2f, 1.f}, {-0.2f, 0f, 0.2f, 1.f},
{0.2f, 0f, 0.2f, 1.f}, {0.8f, 0f, 0.2f, 1.f}},
{{-0.6f, 0f, 0.9f, 1.f}, {-0.2f, 0f, 0.5f, 1.f},
{0.2f, 0f, 0.5f, 1.f}, {0.6f, 0f, 0.8f, 1.f}}};
//定义第一个Bezier曲面外观属性
Appearance app1 = new Appearance();
PolygonAttributes polygona1=new PolygonAttributes();
polygona1.setBackFaceNormalFlip(true);
polygona1.setCullFace(PolygonAttributes.CULL_NONE);
polygona1.setPolygonMode(PolygonAttributes.POLYGON_LINE);
app1.setPolygonAttributes(polygona1);
ColoringAttributes color1=new ColoringAttributes();
color1.setColor(0.8f,0.f,0.f);
app1.setColoringAttributes(color1);
float[][][] P2={
{{-0.8f, 0.5f, -0.8f, 1.f}, {-0.2f, 0.5f, -0.5f, 1.f},
{0.2f, 0.5f, -0.5f, 1.f}, {0.8f, 0.5f, -0.8f, 1.f}},
{{-0.8f, 0.5f, -0.2f, 1.f}, {-0.2f, 0.5f, -0.2f, 1.f},
{0.2f, 0.5f, -0.2f, 1.f}, {0.8f, 0.5f, -0.2f, 1.f}},
{{-0.8f, 0.5f, 0.2f, 1.f}, {-0.2f, 0.5f, 0.2f, 1.f},
{0.2f, 0.5f, 0.2f, 1.f}, {0.8f, 0.5f, 0.2f, 1.f}},
{{-0.6f, 0.5f, 0.9f, 1.f}, {-0.2f, 0.5f, 0.5f, 1.f},
{0.2f, 0.5f, 0.5f, 1.f}, {0.6f, 0.5f, 0.8f, 1.f}}};
//定义第一个Bezier曲面外观属性
Appearance app2 = new Appearance();
PolygonAttributes polygona2=new PolygonAttributes();
polygona2.setBackFaceNormalFlip(true);
polygona2.setCullFace(PolygonAttributes.CULL_NONE);
polygona2.setPolygonMode(PolygonAttributes.POLYGON_LINE);
app2.setPolygonAttributes(polygona2);
ColoringAttributes color2=new ColoringAttributes();
color2.setColor(0.8f,0.f,0.f);
app2.setColoringAttributes(color2);
Shape3D BezierSurfaceface2=new BezierThreeOrderSurfaceface(P2,app2);
transformgroup.addChild(BezierSurfaceface2);
Shape3D BezierSurfaceface1=new BezierThreeOrderSurfaceface(P1,app1);
transformgroup.addChild(BezierSurfaceface1);
BranchGroupRoot.compile();
return BranchGroupRoot;
}
public BezierSurfaceMerging()
{setLayout(new BorderLayout());
GraphicsConfiguration gc = SimpleUniverse.getPreferredConfiguration();
Canvas3D c=new Canvas3D(gc);
add("Center",c);
BranchGroup BranchGroupScene=createBranchGroupSceneGraph();
SimpleUniverse u=new SimpleUniverse(c);
u.getViewingPlatform().setNominalViewingTransform();
u.addBranchGraph(BranchGroupScene);
}
public static void main(String[] args)
{new Mainframe(new BezierSurfaceMerging(),400,400); }
}
class BezierThreeOrderSurfaceface extends Shape3D
{public BezierThreeOrderSurfaceface(float[][][] P,Appearance app)
{int i,j,k;
int n0;//定义对参数u、v在[0，1]区间的等分点数
float division;//参数u在[0，1]区间的等分线段长度
n0=50;division=1.f/n0;
//分别定义存放控制顶点x、y、z坐标与第四维坐标的数组
float[][] PX=new float[4][4];
float[][] PY=new float[4][4];
float[][] PZ=new float[4][4];
float[][] P4=new float[4][4];
//定义系数矩阵及其转置矩阵
float[][] M1={{1.f,0.f,0.f,0.f},
{-3.f,3.f,0.f,0.f},
{3.f,-6.f,3.f,0.f},
{-1.f,3.f,-3.f,1.f}};
float[][] M2={{1.f,-3.f,3.f,-1.f},
{0.f,3.f,-6.f,3.f},
{0.f,0.f,3.f,-3.f},
{0.f,0.f,0.f,1.f}};
//定义Bezier曲面的u、v参数分割点坐标数组
float[][][] UV=new float[n0+1][n0+1][2];
//定义U、V矩阵数组
float[][] UU=new float[1][4];
float[][] VV=new float[4][1];
//定义存放曲面上点的坐标的数组
float[][][] SurfaceXYZ=new float[n0+1][n0+1][4];
for(i=0;i
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