Hello Rooters, If you create a Arc with: TArc *Arc = new TArc (0,0,1,90,180); Arc->Draw(); you should obtain a quarter of circle in the upper-left corner of the picture, but you obtain it on the upper-RIGHT corner. It seems to me that this bug is in the function TEllipse::PaintEllipse: the rotation angle theta is taken into account, but not the first angle phimin: void TEllipse::PaintEllipse(Float_t, Float_t, Float_t, Float_t, Float_t phimin,Float_t phimax, Float_t theta) { //*-*-*-*-*-*-*-*-*-*-*Draw this ellipse with new coordinates*-*-*-*-*-*-*-*-* //*-* ====================================== const Int_t np = 40; const Float_t PI = 3.141592; static Float_t x[np+2], y[np+2]; TAttLine::Modify(); //Change line attributes only if necessary TAttFill::Modify(); //Change fill attributes only if necessary Float_t angle,dx,dy; Float_t dphi = (phimax-phimin)*PI/(180*np); Float_t ct = TMath::Cos(PI*theta/180); Float_t st = TMath::Sin(PI*theta/180); for (Int_t i=0;i<np;i++) { angle = Float_t(i)*dphi; ---------> I think, one must add 'phimin' to this 'angle'! dx = fR1*TMath::Cos(angle); dy = fR2*TMath::Sin(angle); x[i] = fX1 + dx*ct - dy*st; y[i] = fY1 + dx*st + dy*ct; } if (phimax-phimin >= 360 ) { x[np] = x[0]; y[np] = y[0]; if (GetFillColor()) gPad->PaintFillArea(np,x,y); if (GetLineStyle()) gPad->PaintPolyLine(np+1,x,y); } else { x[np] = fX1; y[np] = fY1; x[np+1] = x[0]; y[np+1] = y[0]; if (GetFillColor()) gPad->PaintFillArea(np+1,x,y); if (GetLineStyle()) gPad->PaintPolyLine(np+2,x,y); } } -------------------------------------------- A suggestion: Would it be possible to provide an option to draw only the contour of the ellipse, without the lines joining the center? Thank you -------------------------------------------- Mathieu de Naurois LPNHE Ecole Polytechnique denauroi@polhp1.inp3.fr
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