   line equation
  Hi!I'm new to gamedev and game programming.Can anybody give me equation of line basically x=y and z = 0 in 3d space.(This is same x=y in 2d).   
  In 3d you can only define surfaces with equations like z=... (if you use carthesian coordinates and no complex values).You can define a line by the combination of two planes: ax +by +cz +d=0 and ex + fy + gz + h =0. All points that are valid for both equations are on a line, the example you gave is also of this form.I find it easier this way:A line is defined by 2 points: (x1,y1,z1) and (x2, y2, z2)Or by 1 point and a direction: point(x1y1,z1) direction(x2-x1,y2-y1, z2-z1)then the line can be written as: (x1y1,z1)+k(x2-x1,y2-y1, z2-z1)where k is any value you want. If the direction is normalized, k is the distance from the point you mean to (x1y1,z1)