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# Nurbs Equations/Algorithms

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Ok i have all i need to do just about anything i want to with NURBS using equations. The problem is that i dont understand the equations enough to convert them to code. I know my math up through lower calculus, but these equations are way up there. Ok here we go,   sum(i = 0, n){w_i * P_i * N_i,k(u)} C(u) = -------------------------------------   sum(i = 0, n){w_i * N_i,k(u)} This is a NURBS equation where w_i : weights P_i : control points (vector) N_i,k : normalized B-spline basis functions of degree k this is supposed to be an equation(or something) that projects a 4D point onto the plane w=1         { ( wx/w, wy/w, wz/w) if w !=0 H(wx,wy,wz,w)={         { ( direction(wx, wy) if w = 0 These variables are the part i dont get. I dont understand how to incorperate P_i as a vector I think w_i is a vector too but i dont know. Any help with these equations will be greatly apriciated. Any help on how to draw 2D NURBS curves, will work too. I can figure out how to convert to 3D later. Oh, and if any of you have any code for open GL that draws just pixels (as in PlotPixel(x,y,R,G,B) that would be nice too. thanks for you help. the alignment on the equations is alittle messed up on the seconed equation you need to line up the '{' to make it look right, by the way the '{' are really supposed to be one big '{'. The first equation looks ok but not perfect. Edited by - warpexplorer on 10/5/00 10:50:12 PM

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