已知三维点p1,p2,p3,求p4.

Question

p1、p2、p4在同一条真线上
p3不在p1、p2上
p1p2垂直于p3p4
谁有现成的开发包或计算公式

Answer 1

                               ·P3
                               |
                               |
                               |
                               |
——·—————·—————————·P4
    P1         P2              或者
                               ·P3
                               |
                               |
                               |
                               |
——·—————·—————————·P4
    P1         P2              |
                               |
                               |
                               |

Answer 2

上面的显示不好                              ·P3 
                              | 
                              | 
                              | 
                              | 
——·—————·——————·P4 
    P1        P2              或者 
                              ·P3 
                              | 
                              | 
                              | 
                              | 
——·—————·——————·P4 
    P1        P2              | 
                              | 
                              | 
                              |

Answer 3

就是求p3在直线p1p2上面的投影坐标p4吧。 float len = ((x3 - x1)*(x2-x1) + (y3 - y1)*(y2-y1) + (z3 - z1)*(z2-z1))
/ ((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) + (z2-z1)*(z2-z1)); x4 = x1 + (x2 - x1)*len;
y4 = y1 + (y2 - y1)*len;
z4 = z1 + (z2 - z1)*len;如果是二维的，请将z设置为0。

Answer 4

http://www.cnblogs.com/microsoftxiao/archive/2007/03/03/662837.html