如何理解JavaFX三角网格？ [英] How to make sense of JavaFX triangle mesh?
问题描述
试图理解JavaFX文档重新三角形网格。
此代码可以工作并绘制一个矩形。
Just trying to make sense of JavaFX documentation re triangle mesh. This code works and draws a rectangle.
public class Shape3DRectangle extends TriangleMesh {
public Shape3DRectangle(float Width, float Height) {
float[] points = {
-Width/2, Height/2, 0, // idx p0
-Width/2, -Height/2, 0, // idx p1
Width/2, Height/2, 0, // idx p2
Width/2, -Height/2, 0 // idx p3
};
float[] texCoords = {
1, 1, // idx t0
1, 0, // idx t1
0, 1, // idx t2
0, 0 // idx t3
};
/**
* points:
* 1 3
* ------- texture:
* |\ | 1,1 1,0
* | \ | -------
* | \ | | |
* | \ | | |
* | \| -------
* ------- 0,1 0,0
* 0 2
*
* texture[3] 0,0 maps to vertex 2
* texture[2] 0,1 maps to vertex 0
* texture[0] 1,1 maps to vertex 1
* texture[1] 1,0 maps to vertex 3
*
* Two triangles define rectangular faces:
* p0, t0, p1, t1, p2, t2 // First triangle of a textured rectangle
* p0, t0, p2, t2, p3, t3 // Second triangle of a textured rectangle
*/
int[] faces = {
2, 2, 1, 1, 0, 0,
2, 2, 3, 3, 1, 1
};
this.getPoints().setAll(points);
this.getTexCoords().setAll(texCoords);
this.getFaces().setAll(faces);
}
}
评论的最后3行来自 Class TriangleMesh 。我的问题是我没有看到faces数组的定义和代码中的faces数组之间的匹配。因此，对于其他情况，一般不了解如何使用faces数组。不应该是这样：
The last 3 lines of the comment come from Class TriangleMesh. My problem is that I do not see a match between their definition of the faces array and the faces array in the code. Thus don't understand how to use faces array in general for other cases. Should it not be this instead:
int[] faces = {
2, 3, 0, 2, 1, 0,
2, 3, 1, 0, 3, 1
};
然后没有渲染矩形。
我缺少什么，一般应该进入faces数组？
But then nothing renders of the rectangle. What am I missing and what should go into the faces array in general?
推荐答案
如何解释面部方向有效
定义面部的方向很重要。在工作样本中，第一面的点是2,1,0（即，三角形以逆时针顺序定义）。在你建议的faces数组中，第一个面是2,0,1（顺时针）。以顺时针方式限定的面背向观察者。以逆时针方式限定的面朝向观察者。
The direction in which the face is defined is important. In the working sample, the point of the first face is 2, 1, 0 (i.e. the triangle is defined in a counter-clockwise order). In the faces array you suggest, the first face is 2, 0, 1 (clockwise). A face which is defined in a clockwise manner faces away from the viewer. A face which is defined in a counter-clockwise manner faces toward the viewer.
如何使网格可见
如果您采用建议的面部定义并围绕Y轴旋转网格180度，您将看到面部。如果没有网格的旋转，您将默认查看面部的背面，并且网格的背面将被剔除（即不可见）。
If you take your suggested face definition and rotate the mesh 180 degrees round the Y axis, you will see the face. Without rotation of the mesh, you will by default be looking at the back of the face, and the back of the mesh will be culled (i.e. not visible).
另一种无需旋转即可看到网格的方法是将网格的剔除面设置为 CullFace.NONE ，然后网格的背面将显示（虽然它只显示为黑色而不是阴影区域）。
Another way to see your mesh without rotation is to set the cull face of the Mesh to CullFace.NONE, then the back of the mesh will show (though as it will just show as black rather than a shaded region).
关于您提供的代码中的注释的说明
您的代码示例中的注释略有误导，它应该反映实际的面部定义而不是实际上没有按预期工作的面部定义。
The comment in your code sample is slightly misleading, it should reflect the the actual face definition rather than a face definition which doesn't really work as expected.
文档请求更改建议
IMO， TriangleMesh 文档，我在<啊记录了一个更改请求ref =https://javafx-jira.kenai.com =noreferrer>针对运行时项目的JavaFX问题跟踪器以请求此增强功能。
IMO, the TriangleMesh documentation should be enhanced, I logged a change request in the JavaFX issue tracker against the runtime project to request this enhancement.
更改文档请求以突出显示网格面中点的顺序为：
Change request for documentation to highlight ordering of points in mesh faces is:
RT-34292文件TriangleMesh元素顺序的重要性
Java 8 3D API文档的伞更改请求是：
Umbrella change request for documentation of the Java 8 3D API is:
RT-26385完成适用于FX 8 3D API的javadoc
演示
这是您可以使用示例测试工具来更好地理解它们。
Here is a sample test harness you can use for playing around with this concepts in order to understand them better.
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.*;
import javafx.scene.input.MouseEvent;
import javafx.scene.paint.*;
import javafx.scene.shape.*;
import javafx.scene.transform.Rotate;
import javafx.stage.Stage;
// drag the mouse over the rectangle to rotate it.
public class RectangleViewer extends Application {
double anchorX, anchorY, anchorAngle;
private PerspectiveCamera addCamera(Scene scene) {
PerspectiveCamera perspectiveCamera = new PerspectiveCamera(false);
scene.setCamera(perspectiveCamera);
return perspectiveCamera;
}
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) {
final MeshView rect = new MeshView(
new Shape3DRectangle(200, 200)
);
rect.setMaterial(new PhongMaterial(Color.DARKGREEN));
rect.setRotationAxis(Rotate.Y_AXIS);
rect.setTranslateX(250);
rect.setTranslateY(250);
// try commenting this line out to see what it's effect is . . .
rect.setCullFace(CullFace.NONE);
final Group root = new Group(rect);
final Scene scene = new Scene(root, 500, 500, true);
scene.setOnMousePressed(new EventHandler<MouseEvent>() {
@Override public void handle(MouseEvent event) {
anchorX = event.getSceneX();
anchorY = event.getSceneY();
anchorAngle = rect.getRotate();
}
});
scene.setOnMouseDragged(new EventHandler<MouseEvent>() {
@Override public void handle(MouseEvent event) {
rect.setRotate(anchorAngle + anchorX - event.getSceneX());
}
});
addCamera(scene);
primaryStage.setScene(scene);
primaryStage.show();
}
public class Shape3DRectangle extends TriangleMesh {
public Shape3DRectangle(float Width, float Height) {
float[] points = {
-Width/2, Height/2, 0, // idx p0
-Width/2, -Height/2, 0, // idx p1
Width/2, Height/2, 0, // idx p2
Width/2, -Height/2, 0 // idx p3
};
float[] texCoords = {
1, 1, // idx t0
1, 0, // idx t1
0, 1, // idx t2
0, 0 // idx t3
};
/**
* points:
* 1 3
* ------- texture:
* |\ | 1,1 1,0
* | \ | -------
* | \ | | |
* | \ | | |
* | \| -------
* ------- 0,1 0,0
* 0 2
*
* texture[3] 0,0 maps to vertex 2
* texture[2] 0,1 maps to vertex 0
* texture[0] 1,1 maps to vertex 1
* texture[1] 1,0 maps to vertex 3
*
* Two triangles define rectangular faces:
* p0, t0, p1, t1, p2, t2 // First triangle of a textured rectangle
* p0, t0, p2, t2, p3, t3 // Second triangle of a textured rectangle
*/
// if you use the co-ordinates as defined in the above comment, it will be all messed up
// int[] faces = {
// 0, 0, 1, 1, 2, 2,
// 0, 0, 2, 2, 3, 3
// };
// try defining faces in a counter-clockwise order to see what the difference is.
// int[] faces = {
// 2, 2, 1, 1, 0, 0,
// 2, 2, 3, 3, 1, 1
// };
// try defining faces in a clockwise order to see what the difference is.
int[] faces = {
2, 3, 0, 2, 1, 0,
2, 3, 1, 0, 3, 1
};
this.getPoints().setAll(points);
this.getTexCoords().setAll(texCoords);
this.getFaces().setAll(faces);
}
}
}
演示输出
当绘制矩形时，矩形网格的正面和背面默认面向观察者（通过沿顺时针方向定义面）和使用CullFace.NONE设置（win7 jdkb115）。
Front and back faces of the rectangle mesh when the rectangle is drawn to be by default facing away the viewer (by defining a face in a clockwise direction) and with a CullFace.NONE setting (win7 jdkb115).
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