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[hist] implement new POLF and POLN draw options #22913

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c94ac52
[hist] use internal variable to preserve histogram draw range
linev Jul 24, 2026
5f5abb6
[hist] introduce POLF draw option
linev Jul 24, 2026
4015770
[hist] introduce POLN draw option
linev Jul 24, 2026
1c4cc61
[hist] mention POLN and POLF draw options in documentation
linev Jul 24, 2026
97f9697
[hist] shift angle range in polar coordinates
linev Jul 24, 2026
4b779d7
[hist] add new POLF/POLN draw options to release notes
linev Jul 24, 2026
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11 changes: 11 additions & 0 deletions README/ReleaseNotes/v642/index.md
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Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,17 @@ or read the bin count from the relevant histogram or plot frame instead.

## Graphics and GUI

### New POLF and POLN draw options for TH2

Since ROOT 6.36 implementation of "POL" draw option was changed. Angle and radius range automatically scaled to visible histogram range filling full 2*Pi angle and full radius range.
This let display TH2 in polar coordinates for any provided range settings, but produced plots are not intuitive. Therefore two new options for polar coordinates were introduced.

"POLF" - fixed polar coordinates. In such case full histogram X range mapped to -PI .. +Pi.
And Y axis mapped to radius. In case of histogram zooming angle and radius of each bin remains
the same (therefore name "fixed"), just number of displayed bins are reduced.

"POLN" - natural polar coordinates. In this case X axis directly represents angle value in radians (therefore name "natural") and Y axis is just radius.

### Store canvas as HTML file

Now canvas (or several canvases) can be stored in portable HTML file.
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1 change: 1 addition & 0 deletions hist/histpainter/inc/Hoption.h
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Expand Up @@ -41,6 +41,7 @@ typedef struct Hoption_t {
int Box; ///< <b>"BOX"</b> Draw 2D plot with proportional Boxes.
int Char; ///< <b>"CHAR"</b> Draw 2D plot with a character set.
int Color; ///< <b>"COL"</b> Draw 2D plot with Colored boxes.
int Polar; ///< <b>"POL"</b> Draw 2D plot with Polar coordinates.
int Contour; ///< <b>"CONTn"</b> Draw 2D plot as a Contour plot (0 <= n <= 5).
int Func; ///< <b>"FUNC"</b> Draw only the function (for example in case of fit).
int Hist; ///< <b>"HIST"</b> Draw only the histogram.
Expand Down
119 changes: 84 additions & 35 deletions hist/histpainter/src/THistPainter.cxx
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Expand Up @@ -309,7 +309,9 @@ using `TH1::GetOption`:
| "SAME0" | Same as "SAME" but do not use the z-axis range of the first plot. |
| "SAMES0" | Same as "SAMES" but do not use the z-axis range of the first plot. |
| "CYL" | Use Cylindrical coordinates. The X coordinate is mapped on the angle and the Y coordinate on the cylinder length.|
| "POL" | Use Polar coordinates. The X coordinate is mapped on the angle and the Y coordinate on the radius.|
| "POL" | Use Polar coordinates. The visible X range mapped on the angle and the visible Y coordinate on the radius.|
| "POLF" | Fixed Polar coordinates. The histogram X coordinate mapped on the angle and the Y coordinate on the radius.|
| "POLN" | Natural Polar coordinates. The X coordinate directly represent angle in radian and the Y coordinate is the radius.|
| "SPH" | Use Spherical coordinates. The X coordinate is mapped on the latitude and the Y coordinate on the longitude.|
| "PSR" | Use PseudoRapidity/Phi coordinates. The X coordinate is mapped on Phi.|
| "SURF" | Draw a surface plot with hidden line removal.|
Expand Down Expand Up @@ -4063,6 +4065,7 @@ Int_t THistPainter::MakeChopt(Option_t *choptin)
Hoption.Lego = Hoption.Surf = Hoption.Off = Hoption.Tri = 0;
Hoption.Proj = Hoption.AxisPos = Hoption.Spec = Hoption.Pie = 0;
Hoption.Candle = 0;
Hoption.Polar = 0;

// special 2D options
Hoption.List = 0;
Expand Down Expand Up @@ -4334,7 +4337,9 @@ Int_t THistPainter::MakeChopt(Option_t *choptin)
l = strstr(chopt,"AXIS"); if (l) { Hoption.Axis = 1; memcpy(l," ",4); }
l = strstr(chopt,"AXIG"); if (l) { Hoption.Axis = 2; memcpy(l," ",4); }
l = strstr(chopt,"SCAT"); if (l) { Hoption.Scat = 1; memcpy(l," ",4); }
l = strstr(chopt,"POL"); if (l) { Hoption.System = kPOLAR; memcpy(l," ",3); }
l = strstr(chopt,"POLN"); if (l) { Hoption.System = kPOLAR; Hoption.Polar = 3; memcpy(l," ",4); }
l = strstr(chopt,"POLF"); if (l) { Hoption.System = kPOLAR; Hoption.Polar = 2; memcpy(l," ",4); }
l = strstr(chopt,"POL"); if (l) { Hoption.System = kPOLAR; Hoption.Polar = 1; memcpy(l," ",3); }
l = strstr(chopt,"CYL"); if (l) { Hoption.System = kCYLINDRICAL; memcpy(l," ",3); }
l = strstr(chopt,"SPH"); if (l) { Hoption.System = kSPHERICAL; memcpy(l," ",3); }
l = strstr(chopt,"PSR"); if (l) { Hoption.System = kRAPIDITY; memcpy(l," ",3); }
Expand Down Expand Up @@ -5838,15 +5843,50 @@ void THistPainter::PaintColorLevels(Option_t*)

// Initialize the levels on the Z axis
Int_t ncolors = gStyle->GetNumberOfColors();
Int_t ndiv = fH->GetContour();
if (ndiv == 0 ) {
Int_t ndiv = fH->GetContour();
if (ndiv == 0) {
ndiv = gStyle->GetNumberContours();
fH->SetContour(ndiv);
}
Int_t ndivz = TMath::Abs(ndiv);
if (!fH->TestBit(TH1::kUserContour)) fH->SetContour(ndiv);
Double_t scale = (dz ? ndivz / dz : 1.0);

Double_t xmin = gPad->GetUxmin();
Double_t xmax = gPad->GetUxmax();
Double_t ymin = gPad->GetUymin();
Double_t ymax = gPad->GetUymax();

// range used for polar coordinates
Double_t pxmin = xmin, pxmax = xmax, pymin = ymin, pymax = ymax;
if ((Hoption.System == kPOLAR) && (Hoption.Polar > 1)) {
pxmin = fXaxis->GetXmin();
pxmax = fXaxis->GetXmax();
if (Hoption.Logx) {
if (pxmax <= 0)
return;
pxmax = TMath::Log10(pxmax);
if (pxmin <= 0)
pxmin = pxmax - 5;
else
pxmin = TMath::Log10(pxmin);
}
pymin = fYaxis->GetXmin();
pymax = fYaxis->GetXmax();
if (Hoption.Logy) {
if (pymax <= 0)
return;
pymax = TMath::Log10(pymax);
if (pymin <= 0)
pymin = pymax - 5;
else
pymin = TMath::Log10(pymin);
} else if ((pymax > 0) && (pymin >= 0)) {
// force minimal radius to 0 to display natural polar graphics
pymin = 0;
}
}

Int_t color;
TProfile2D* prof2d = dynamic_cast<TProfile2D*>(fH);
for (Int_t j=Hparam.yfirst; j<=Hparam.ylast;j++) {
Expand All @@ -5873,35 +5913,36 @@ void THistPainter::PaintColorLevels(Option_t*)
}
}

if (Hoption.Logz) {
if (z > 0) z = TMath::Log10(z);
else z = zmin;
}
if (z < zmin && !Hoption.Zero) continue;
if (Hoption.Logz)
z = z > 0 ? TMath::Log10(z) : zmin;
if (z < zmin && !Hoption.Zero)
continue;
xup = xk + xstep;
xlow = xk;
if (Hoption.Logx) {
if (xup > 0) xup = TMath::Log10(xup);
else continue;
if (xlow > 0) xlow = TMath::Log10(xlow);
else continue;
if ((xup <= 0) || (xlow <= 0))
continue;
xup = TMath::Log10(xup);
xlow = TMath::Log10(xlow);
}
yup = yk + ystep;
ylow = yk;
if (Hoption.Logy) {
if (yup > 0) yup = TMath::Log10(yup);
else continue;
if (ylow > 0) ylow = TMath::Log10(ylow);
else continue;
}
if (xup < gPad->GetUxmin()) continue;
if (yup < gPad->GetUymin()) continue;
if (xlow > gPad->GetUxmax()) continue;
if (ylow > gPad->GetUymax()) continue;
if (xlow < gPad->GetUxmin()) xlow = gPad->GetUxmin();
if (ylow < gPad->GetUymin()) ylow = gPad->GetUymin();
if (xup > gPad->GetUxmax()) xup = gPad->GetUxmax();
if (yup > gPad->GetUymax()) yup = gPad->GetUymax();
if ((yup <= 0) || (ylow <= 0))
continue;
yup = TMath::Log10(yup);
ylow = TMath::Log10(ylow);
}
if ((xup < xmin) || (yup < ymin) || (xlow > xmax) || (ylow > ymax))
continue;
if (xlow < xmin)
xlow = xmin;
if (ylow < ymin)
ylow = ymin;
if (xup > xmax)
xup = xmax;
if (yup > ymax)
yup = ymax;

if (fH->TestBit(TH1::kUserContour)) {
zc = fH->GetContourLevelPad(0);
Expand All @@ -5920,21 +5961,29 @@ void THistPainter::PaintColorLevels(Option_t*)
}

Int_t theColor = Int_t((color+0.99)*Float_t(ncolors)/Float_t(ndivz));
if (theColor > ncolors-1) theColor = ncolors-1;
if (theColor > ncolors-1)
theColor = ncolors-1;
auto fillColor = gStyle->GetColorPalette(theColor);
if (Hoption.System != kPOLAR) {
fH->SetFillColor(fillColor);
fH->TAttFill::Modify();
gPad->PaintBox(xlow, ylow, xup, yup);
} else {
Double_t midx = (gPad->GetUxmin() + gPad->GetUxmax()) / 2,
midy = (gPad->GetUymin() + gPad->GetUymax()) / 2,
a1 = (xlow - gPad->GetUxmin()) / (gPad->GetUxmax() - gPad->GetUxmin()) * 360,
a2 = (xup - gPad->GetUxmin()) / (gPad->GetUxmax() - gPad->GetUxmin()) * 360,
rx = gPad->GetUxmax() - gPad->GetUxmin(),
ry = gPad->GetUymax() - gPad->GetUymin(),
r1 = (ylow - gPad->GetUymin()) / (gPad->GetUymax() - gPad->GetUymin()) * rx / 2,
r2 = (yup - gPad->GetUymin()) / (gPad->GetUymax() - gPad->GetUymin()) * rx / 2;
Double_t midx = (xmin + xmax) / 2;
Double_t midy = (ymin + ymax) / 2;
Double_t rx = xmax - xmin;
Double_t ry = ymax - ymin;
Double_t a1, a2;

if (Hoption.Polar == 3) {
a1 = xlow / TMath::Pi() * 180;
a2 = xup / TMath::Pi() * 180;
} else {
a1 = ((xlow - pxmin) / (pxmax - pxmin) - 0.5) * 360;
a2 = ((xup - pxmin) / (pxmax - pxmin) - 0.5) * 360;
}
Double_t r1 = (ylow - pymin) / (pymax - pymin) * rx / 2;
Double_t r2 = (yup - pymin) / (pymax - pymin) * rx / 2;

TCrown crown(midx, midy, r1, r2, a1, a2);
crown.SetYXRatio(rx > 0 ? ry / rx : 1);
Expand Down
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