java 游戏编程 (十)

这篇主要说纹理贴图问题
纹理中的像素为图素 texeture element 纹理是根据镜头与多边形的距离缩放，图素也会缩放。

将每个像素贴图一个图素，就可以贴图。就是说读取一个图，获取这个图的每个点的像素，然后贴到视图窗口的每个像素。

计算方法：
纹理贴图的计算方程

x=U·(P-0)  Y=V·(P-0)
视图窗口中的一个点在多边形上的具体点P

z/x=pz/px 顶点用W表示的话，W=(d/pz)/p
要找到点P，就要找到PZ，平面的发现N和平面上的直线是正交
N·(P-0)=0
N·0=N·P
推导过程我就不写了
最后
x=(-v*w·0)/(u*v·w)
用类描述纹理,纹理是三维空间中的矩形
Rectangle3D

package com.jsheng.game.util.java3d.texture;

import com.jsheng.game.util.java3d.Transform3D;
import com.jsheng.game.util.java3d.Vector3D;

public class Rectangle3D {
	private Vector3D origin;		//原点
	private Vector3D directionU;	//方程中的U
	private Vector3D directionV;	//方程中的V
	private Vector3D normal;		//法线
	private float width;
	private float height;

	public Rectangle3D() {
		origin = new Vector3D();
		directionU = new Vector3D(1, 0, 0);
		directionV = new Vector3D(0, 1, 0);
		width = 0;
		height = 0;
	}

	public Rectangle3D(Vector3D origin, Vector3D directionU,
			Vector3D directionV, float width, float height) {
		this.origin = new Vector3D(origin);
		this.directionU = new Vector3D(directionU);
		this.directionU.normalize();
		this.directionV = new Vector3D(directionV);
		this.directionV.normalize();
		this.width = width;
		this.height = height;
	}

	public void setTo(Rectangle3D rect) {
		origin.setTo(rect.origin);
		directionU.setTo(rect.directionU);
		directionV.setTo(rect.directionV);
		width = rect.width;
		height = rect.height;
	}

	protected Vector3D calcNormal() {
		if (normal == null) {
			normal = new Vector3D();
		}
		normal.setToCrossProduct(directionU, directionV);
		normal.normalize();
		return normal;
	}

	public Vector3D getOrigin() {
		return origin;
	}

	public void setOrigin(Vector3D origin) {
		this.origin = origin;
	}

	public Vector3D getDirectionU() {
		return directionU;
	}

	public void setDirectionU(Vector3D directionU) {
		this.directionU = directionU;
	}

	public Vector3D getDirectionV() {
		return directionV;
	}

	public void setDirectionV(Vector3D directionV) {
		this.directionV = directionV;
	}

	public Vector3D getNormal() {
		if (normal == null) {
			calcNormal();
		}
		return normal;
	}

	public void setNormal(Vector3D normal) {
		if (normal == null) {
			normal = new Vector3D(normal);
		} else {
			normal.setTo(normal);
		}
	}

	public float getWidth() {
		return width;
	}

	public void setWidth(float width) {
		this.width = width;
	}

	public float getHeight() {
		return height;
	}

	public void setHeight(float height) {
		this.height = height;
	}

	public void add(Transform3D xform) {
		addRotation(xform);
		add(xform.getLocation());
	}

	public void subtract(Transform3D xform) {
		subtract(xform.getLocation());
		subtractRotation(xform);
	}

	public void add(Vector3D u) {
		origin.add(u);
	}

	public void subtract(Vector3D u) {
		origin.subtract(u);
	}

	public void addRotation(Transform3D myForm) {
		origin.addRotation(myForm);
		directionU.addRotation(myForm);
		directionV.addRotation(myForm);
	}

	public void subtractRotation(Transform3D xform) {
		origin.subtractRotation(xform);
		directionU.subtractRotation(xform);
		directionV.subtractRotation(xform);
	}
}

先到这里，明天修改。