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 Original Message (ID '81794') By Paul: In Response To 'Re: Parametric regionfunction' --------- Hello Bill, thanks for replying to my question. I'll try to make my issue somewhat more understandable: This is the function I'm trying to give a region: ParametricPlot3D[{{uvlak, vvlak, 100 - 0.00222222 uvlak^2 + 0.00636667 vvlak^2 + 0.000027037 vvlak^3 - 5.46296*10^-7 vvlak^4}}, {uvlak, 0, 150}, {vvlak, -100, 0}]] The region itself I've got too. This is a parametric function: x1 = ( (1 - u2 )^2*0 + 2 (u2) (1 - u2)*(150) + (u2 )^2*(150)) y1 = ( (1 - u2)^2*-(100) + 2 (u2) (1 - u2)*-(100) + (u2)^2*0) (or: b8 = ParametricPlot3D[{{x1, y1, 0}}, {u2, 0, 1}] When I'm applying this region to my function, it seems like I can't get my region parametric. I think this means I can't get a maximum x(u) at y(u), but a the maximum u at y(u). The same goes for the other orientation. Below is the code that illustrates this problem. I plotted two Parametric3D plots, each with one part of the region and the region itself (as a line). When the regions are combined in one Plot, it cuts off too much (because of the reason above I think). b10 = ParametricPlot3D[{{uvlak, vvlak, 100 - 0.00222222 uvlak^2 + 0.00636667 vvlak^2 + 0.000027037 vvlak^3 - 5.46296*10^-7 vvlak^4}}, {uvlak, 0, 150}, {vvlak, -100, 0}, RegionFunction -> Function[{uvlak, vvlak, zed}, uvlak < (((1 - vvlak + 100)/100)^2*0 + 2 ((1 - vvlak + 100)/100) (1 - (1 - vvlak + 100)/100)*(150) + ((1 - vvlak + 100)/100)^2*(150)) ]] b11 = ParametricPlot3D[{{uvlak, vvlak, 100 - 0.00222222 uvlak^2 + 0.00636667 vvlak^2 + 0.000027037 vvlak^3 - 5.46296*10^-7 vvlak^4}}, {uvlak, 0, 150}, {vvlak, -100, 0}, RegionFunction -> Function[{uvlak, vvlak, zed}, vvlak > ((1 - (uvlak)/150)^2*-(100) + 2 ((uvlak)/ 150) (1 - (uvlak)/150)*-(100) + ((uvlak)/150)^2*0)]] x1 = ( (1 - u2 )^2*0 + 2 (u2) (1 - u2)*(150) + (u2 )^2*(150)) y1 = ( (1 - u2)^2*-(100) + 2 (u2) (1 - u2)*-(100) + (u2)^2*0) b8 = ParametricPlot3D[{{x1, y1, 0}}, {u2, 0, 1}] Show[{b10, b8}, PlotRange -> All] Show[{b11, b8}, PlotRange -> All] So I think the mean problem is that I can't get to work my region like a parametric function. Maybe there's a way to get it working like such.