class TGLHistPainter: public TVirtualHistPainter

The histogram painter class using OpenGL

Histograms are, by default, drawn via the THistPainter class. TGLHistPainter allows to paint them using the OpenGL 3D graphics library. The plotting options provided by TGLHistPainter start with GL keyword.

General information: plot types and supported options

The following types of plots are provided:

• Lego - (TGLLegoPainter)
  The supported options are:
  • "GLLEGO" : Draw a lego plot.
  • "GLLEGO2" : Bins with color levels.
  • "GLLEGO3" : Cylindrical bars.
  Lego painter in cartesian supports logarithmic scales for X, Y, Z. In polar only Z axis can be logarithmic, in cylindrical only Y (if you see what it means).

• Surfaces (TF2 and TH2 with "GLSURF" options) - (TGLSurfacePainter)
  The supported options are:
  • "GLSURF" : Draw a surface.
  • "GLSURF1" : Surface with color levels
  • "GLSURF2" : The same as "GLSURF1" but without polygon outlines.
  • "GLSURF3" : Color level projection on top of plot (works only in cartesian coordinate system).
  • "GLSURF4" : Same as "GLSURF" but without polygon outlines.
  The surface painting in cartesian coordinates supports logarithmic scales along X, Y, Z axis. In polar coordinates only the Z axis can be logarithmic, in cylindrical coordinates only the Y axis.

• Additional options to SURF and LEGO - Coordinate systems:
  The supported options are:
  • " " : Default, cartesian coordinates system.
  • "POL" : Polar coordinates system.
  • "CYL" : Cylindrical coordinates system.
  • "SPH" : Spherical coordinates system.

• TH3 as boxes (spheres) - (TGLBoxPainter)
  The supported options are:
  • "GLBOX" : TH3 as a set of boxes, size of box is proportional to bin content.
  • "GLBOX1": the same as "glbox", but spheres are drawn instead of boxes.

• TH3 as iso-surface(s) - (TGLIsoPainter)
  The supported option is:
  • "GLISO" : TH3 is drawn using iso-surfaces.

• TH3 as color boxes - (TGLVoxelPainter)
  The supported option is:
  • "GLCOL" : TH3 is drawn using semi-transparent colored boxes.
    See $ROOTSYS/tutorials/gl/glvox1.C.

• TF3 (implicit function) - (TGLTF3Painter)
  The supported option is:
  • "GLTF3" : Draw a TF3.

• Parametric surfaces - (TGLParametricPlot)
  $ROOTSYS/tutorials/gl/glparametric.C shows how to create parametric equations and visualize the surface.

Interaction with the plots

• General information.
  All the interactions are implemented via standard methods DistancetoPrimitive and ExecuteEvent. That's why all the interactions with the OpenGL plots are possible i only when the mouse cursor is in the plot's area (the plot's area is the part of a the pad occupied by gl-produced picture). If the mouse cursor is not above gl-picture, the standard pad interaction is performed.

• Selectable parts.
  Different parts of the plot can be selected:
  • xoz, yoz, xoy back planes:
    When such a plane selected, it's highlighted in green if the dynamic slicing by this plane is supported, and it's highlighted in red, if the dynamic slicing is not supported.
  • The plot itself:
    On surfaces, the selected surface is outlined in red. (TF3 and ISO are not outlined). On lego plots, the selected bin is highlihted. The bin number and content are displayed in pad's status bar. In box plots, the box or sphere is highlighted and the bin info is displayed in pad's status bar.

• Rotation and zooming.
  
  • Rotation:
    When the plot is selected, it can be rotated by pressing and holding the left mouse button and move the cursor.
  • Zoom/Unzoom:
    Mouse wheel or 'j', 'J', 'k', 'K' keys.

• Panning.
  The selected plot can be moved in a pad's area by pressing and holding the left mouse button and the shift key.

Box cut

Surface, iso, box, TF3 and parametric painters support box cut by pressing the 'c' or 'C' key when the mouse cursor is in a plot's area. That will display a transparent box, cutting away part of the surface (or boxes) in order to show internal part of plot. This box can be moved inside the plot's area (the full size of the box is equal to the plot's surrounding box) by selecting one of the box cut axes and pressing the left mouse button to move it.

Plot specific interactions (dynamic slicing etc.)

Currently, all gl-plots support some form of slicing. When back plane is selected (and if it's highlighted in green) you can press and hold left mouse button and shift key and move this back plane inside plot's area, creating the slice. During this "slicing" plot becomes semi-transparent. To remove all slices (and projected curves for surfaces) - double click with left mouse button in a plot's area.

• Surface with option "GLSURF"
  The surface profile is displayed on the slicing plane. The profile projection is drawn on the back plane by pressing 'p' or 'P' key.

• TF3
  The contour plot is drawn on the slicing plane. For TF3 the color scheme can be changed by pressing 's' or 'S'.

• Box
  The contour plot corresponding to slice plane position is drawn in real time.

• Iso
  Slicing is similar to "GLBOX" option.

• Parametric plot
  No slicing. Additional keys: 's' or 'S' to change color scheme - about 20 color schemes supported ('s' for "scheme"); 'l' or 'L' to increase number of polygons ('l' for "level" of details), 'w' or 'W' to show outlines ('w' for "wireframe").