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geometric

Some geometric calculations

Representation

2D

  • Line

    • [a, b, c] for $$ax+by+c=0$$, where $$\sqrt{a^2+b^2}=1$$
  • Circle

    • [[a, b], r, [0.0, 0.0, 1.0, 0.0]] for $$(x-a)^2+(y-b)^2=r^2$$
    • The last term, [0.0, 0.0, 1.0, 0.0]], means that the circle lies in the plane $$z=0$$, which is ignorable

3D

  • Line
    • [[a, b, c], [r, s, t]] for $$x=a+rk$$ $$y=b+sk$$ $$z=c+tk$$, where $$\sqrt{r^2+s^2+t^2}=1,k\in\mathbb{R}$$
  • Plane
    • [a, b, c, d] for $$ax+by+cz+d=0$$, where $$\sqrt{a^2+b^2+c^2}=1$$
  • Circle
    • [[x_c, y_c, z_c], r, [a, b, c, d]] for circle lies in plane [a, b, c, d], center at [x_c, y_c, z_c] and with radius r
  • Sphere
    • [[a, b, c], r] for sphere center at [a, b, c] and with radius r
  • Cylinder
    • [[a, b, c], h, r, [nx, ny, nz]] where
      • [a, b, c] is the center of the base circle in 3D space
      • h and r are the height and the radius of the cylinder, respectively
      • [nx, ny, nz] is the direction vector of the cylinder's direction axis