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[graph2d] avoid float arithmetic uncertainties in exclusion plots #20144

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Merged
merged 2 commits into from
Oct 23, 2025
+13 −12
Merged

[graph2d] avoid float arithmetic uncertainties in exclusion plots #20144

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2526f65
[graf2d] use Pi constants for exclusion area painting
linev Oct 20, 2025
20003a3
[graf2d] Use epsilon for exclusion points optimization
linev Oct 20, 2025
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25 changes: 13 additions & 12 deletions hist/histpainter/src/TGraphPainter.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -4696,13 +4696,13 @@ void TGraphPainter::PaintPolyLineHatches(TGraph *theGraph, Int_t n, const Double
} else {
a1 = TMath::ATan((yi1-yi0)/(xi1-xi0));
}
if (xi1<xi0) a1 = a1+3.14159;
if (xi1<xi0) a1 = a1+TMath::Pi();
if (xi2==xi0) {
a2 = TMath::PiOver2();
} else {
a2 = TMath::ATan((yi0-yi2)/(xi0-xi2));
}
if (xi0<xi2) a2 = a2+3.14159;
if (xi0<xi2) a2 = a2+TMath::Pi();
x1 = xi0-w*TMath::Sin(a1);
y1 = yi0+w*TMath::Cos(a1);
x2 = xi0-w*TMath::Sin(a2);
Expand All @@ -4714,8 +4714,8 @@ void TGraphPainter::PaintPolyLineHatches(TGraph *theGraph, Int_t n, const Double
} else {
a3 = TMath::ATan((ym-yi0)/(xm-xi0));
}
x3 = xi0-w*TMath::Sin(a3+1.57079);
y3 = yi0+w*TMath::Cos(a3+1.57079);
x3 = xi0-w*TMath::Sin(a3+TMath::PiOver2());
y3 = yi0+w*TMath::Cos(a3+TMath::PiOver2());
// Rotate (x3,y3) by PI around (xi0,yi0) if it is not on the (xm,ym) side.
if ((xm-xi0)*(x3-xi0)<0 && (ym-yi0)*(y3-yi0)<0) {
x3 = 2*xi0-x3;
Expand All @@ -4738,8 +4738,8 @@ void TGraphPainter::PaintPolyLineHatches(TGraph *theGraph, Int_t n, const Double
} else {
a3 = TMath::ATan((ym-yf[0])/(xm-xf[0]));
}
x3 = xf[0]+w*TMath::Sin(a3+1.57079);
y3 = yf[0]-w*TMath::Cos(a3+1.57079);
x3 = xf[0]+w*TMath::Sin(a3+TMath::PiOver2());
y3 = yf[0]-w*TMath::Cos(a3+TMath::PiOver2());
if ((xm-xf[0])*(x3-xf[0])<0 && (ym-yf[0])*(y3-yf[0])<0) {
x3 = 2*xf[0]-x3;
y3 = 2*yf[0]-y3;
Expand All @@ -4754,20 +4754,21 @@ void TGraphPainter::PaintPolyLineHatches(TGraph *theGraph, Int_t n, const Double
Double_t xc, yc, c1, b1, c2, b2;
Bool_t cross = kFALSE;
Int_t nf2 = nf;
const Double_t eps = 1e-12; // float precision
for (i=nf2; i>0; i--) {
for (j=i-1; j>0; j--) {
if (xt[i-1]==xt[i] || xt[j-1]==xt[j]) continue;
if (TMath::Abs(xt[i-1]-xt[i]) < eps || TMath::Abs(xt[j-1]-xt[j]) < eps) continue;
c1 = (yt[i-1]-yt[i])/(xt[i-1]-xt[i]);
b1 = yt[i]-c1*xt[i];
c2 = (yt[j-1]-yt[j])/(xt[j-1]-xt[j]);
b2 = yt[j]-c2*xt[j];
if (c1 != c2) {
if (TMath::Abs(c1 - c2) > eps) {
xc = (b2-b1)/(c1-c2);
yc = c1*xc+b1;
if (xc>TMath::Min(xt[i],xt[i-1]) && xc<TMath::Max(xt[i],xt[i-1]) &&
xc>TMath::Min(xt[j],xt[j-1]) && xc<TMath::Max(xt[j],xt[j-1]) &&
yc>TMath::Min(yt[i],yt[i-1]) && yc<TMath::Max(yt[i],yt[i-1]) &&
yc>TMath::Min(yt[j],yt[j-1]) && yc<TMath::Max(yt[j],yt[j-1])) {
if (xc>TMath::Min(xt[i],xt[i-1])+eps && xc<TMath::Max(xt[i],xt[i-1])-eps &&
xc>TMath::Min(xt[j],xt[j-1])+eps && xc<TMath::Max(xt[j],xt[j-1])-eps &&
yc>TMath::Min(yt[i],yt[i-1])+eps && yc<TMath::Max(yt[i],yt[i-1])-eps &&
yc>TMath::Min(yt[j],yt[j-1])+eps && yc<TMath::Max(yt[j],yt[j-1])-eps) {
nf++; xf[nf] = xt[i]; yf[nf] = yt[i];
nf++; xf[nf] = xc ; yf[nf] = yc;
i = j;
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