8.5.3 Edge setup linear case8.5.3.1 Mathematical backgroundTo setup a linear edge you can look at the line equation in the classical form:bxay ~~ +=If you rewrite this you can write it as:cybxabyxayxf +⋅+⋅=+−⋅== ~~),(0with bcbaa ~,1,~ =−==This is a more general form. Lets look at a vector form withcnpcybxayxfbanyxp +⋅=+⋅+⋅=⇒== ),(,If a point 0p is on the line thennpccnpyxf ⋅−=⇒+⋅== 00),(0If you rewrite the constant the equation looks like this:( ) nppyxfnpc ⋅−=⇒⋅−= 00 ),(The vector n is called the normal vector and it is perpendicular to the line. Thesetup can be seen in the next image.nOp0p 0pp −dDrawing Engine Chapter 8Preliminary User's Manual S19203EE1V3UM00 227
