在学习微分方程的时候，以前也写过类似的文章，可是效果不行，前几天写了一个，感觉不错，分享之。
先看效果（x*x -y -2）：
再来代码：
[java]
package com.math.slopfields;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;
public class SlopFields extends JFrame {
protected static final int WIDTH = 800;
protected static final int HEIGHT = 600;
private java.awt.Dimension dimension = java.awt.Toolkit.getDefaultToolkit().
getScreenSize();
public SlopFields(String title, Grid g) {
super(title);
this.setSize(WIDTH, HEIGHT);
this.setLocation((dimension.width - WIDTH) / 2,
(dimension.height - HEIGHT) / 2);
HeartCanvas panel = new HeartCanvas(g);
this.add(panel);
}
public static void main(String[] args) {
double scale = 80;
double aa = 3;
double dd = 0.15;
Area area = new Area(Vector.build(-aa, aa), Vector.build(aa, -aa));
Vector grid = Vector.build(dd, dd);
CanCalc c = new CanCalc(){
public double doCalc(Vector v) {
return v.x*v.x - v.y - 2;
}
};
Grid g = new Grid(area, grid, c, scale);
SlopFields hart = new SlopFields("向量场", g);
hart.setVisible(true);
hart.setDefaultCloseOperation(hart.EXIT_ON_CLOSE);
}
}
class HeartCanvas extends javax.swing.JPanel {
private Grid grid;
public HeartCanvas(Grid g) {
this.grid = g;
this.grid.calcGrids();
this.grid.preDraw();
}
public void paintComponent(Graphics g) {
setBackground(Color.BLACK);
super.paintComponent(g);
g.setColor(Color.GREEN);
this.grid.draw(g);
}
}
class Grid {
public double scale = 100;
public double padding = 0.2;
public Vector offect = Vector.build(0.25, 0.25);
public Area area;
public Area[][] areas;
public Vector grid;
public int nx, ny;
private CanCalc calc;
public Grid(Area _area, Vector _grid, CanCalc _calc, double _scale) {
this.area = _area;
this.grid = _grid;
this.calc = _calc;
this.scale = _scale;
}
public void draw(Graphics g) {
int x = (int)area.ld.x;
int y = (int)area.ld.y;
Vector t = area.ru.add(area.ld.neg());
int width = (int)t.x;
int height = (int)t.y;
g.drawRect(x, y, width, height);
g.drawLine(x, (int)offect.y, x+width, (int)offect.y);
g.drawLine((int)offect.x, y, (int)offect.x, y+height);
for(Area[] al : areas) {
for(Area a : al) {
g.drawLine((int)a.ld.x, (int)a.ld.y, (int)a.ru.x, (int)a.ru.y);
}
}
}
public void preDraw() {
offect = offect.dotMul(this.scale).add(Vector.build(-area.ld.x*scale, area.ru.y*scale));
area = new Area(Vector.build(area.ld.x, -area.ru.y).dotMul(this.scale).add(offect),
Vector.build(area.ru.x, -area.ld.x).dotMul(this.scale).add(offect));
for(int i=0; i
Vector va = Vector.build(tmp.ld.x, -tmp.ld.y).dotMul(this.scale).add(offect);