Circumcicle of a triangle
Blitz3D Forums/Blitz3D Beginners Area/Circumcicle of a triangle
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| Hi everyone! I wanted to try out the Delaunay-Triangulation. In the first step I have to create a circumcicle, defined by 3 vertices. But my problem starts already here. I didn't find any useful help in the net how to calculate the coordinates from the circumcicle-center. Can anyone help me please? greetings, Christoph (german-speaking. That's why this post may be full of bad english :-) ) PS: I know how to draw the circumcicle on a piece of paper but I'm not able to do this in Blitz. And I'm at the very beginning of vector-calculation :-( |
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| I not sure what a circumcicle is :o) |
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| There are delaunay examples in the code archives under 3d Graphics / mesh. |
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| Ah, a circumCIRCLE. Can't believe you spelt it wrong 3 times :D Ok, i've had a look and it appears to me like you find the centre point of each of the triangles sides. Then outwardly project a line from each of these until they collide. Now, creating a perpendicular vector should be easy enough. For the centre point, i suggest doing a line intersection equation using 2 of the lines. That should give you your centre point :o) |
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| Thanks! I will look for the examples. In the meantime I found an C-Code and convert it to BB: Global xc#,yc#,r# ;Kreismittelunktkoordinaten und-Radius Const EPSILON#=0.000001 Function CircumCircle(xp#,yp#,x1#,y1#,x2#,y2#,x3#,y3#) Local m1#,m2#,mx1#,mx2#,my1#,my2# Local dx#,dy#,rsqr#,drsqr# If (Abs(y1-y2)<EPSILON And Abs(y2-y3)<EPSILON) Then Return False ElseIf(Abs(y2-y1)<EPSILON)Then m2=-(x3-x2)/(y3-y2) mx2=(x2+x3)/2.0 my2=(y2+y3)/2.0 xc=(x2+x1)/2.0 yc=m2*(xc-mx2)+my2 ElseIf Abs(y3-y2)<EPSILON Then m1=-(x2-x1)/(y2-y1) mx1=(x1+x2)/2.0 my1=(y1+y2)/2.0 xc=(x3+x2)/2.0 yc=m1*(xc-mx1)+my1 Else m1=-(x2-x1)/(y2-y1) m2=-(x3-x2)/(y3-y2) mx1=(x1+x2)/2.0 mx2=(x2+x3)/2.0 my1=(y1+y2)/2.0 my2=(y2+y3)/2.0 xc=(m1*mx1-m2*mx2+my2-my1)/(m1-m2) yc=m1*(xc-mx1)+my1 EndIf dx=x2-xc dy=y2-yc rsqr=dx*dx+dy*dy r=Sqr(rsqr) dx=xp-xc dy=yp-yc drsqr=dx*dx+dy*dy Return (drsqr<=rsqr) End Function But it's only for 2D. best wishes, Christoph PS: Yes, its circumcircle, sorry :-) |
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| i thought the circumference of a triangle is 1/2 B x H...no wait, that's area. ___________________________________________________________ |
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