Graph Contour (2D)
This Select Color Gradient for Surface or Contour option is used to set the contour plot options in graphs. This option incorporates a copy of the current graph. All changes made in any of the contour options are immediately reflected in the graph.
The entry fields serve either the Y or Y2 axis, depending on whether Y Axis or Y2 Axis is selected. The Y2 options will not be available if the graph contains a single plot.
If there are multiple graphs present, the contour settings will apply to all of the graphs.
For the 2D graphing engine, only a square mesh is supported. The nX,nY item is used to set the x and y mesh count of the grid used to evaluate the parametric or non-parametric model interpolating or approximating the 3D surface. A mesh of 60x60 results in 3600 vertices where Z must be computed and a minimum of 3481 major polygons that must be filled. Note that the vertex count can be more than halved by dropping to a 40x40 mesh.
The maximum mesh supported of 300x300 produces 90,000 vertices and 89,401 major polygons. A high mesh offers the best possible resolution in high definition printer output. For such printing, it is recommended that the mesh count be adjusted just prior to printing, and reduced afterward. Very high mesh counts may also assist in revealing regions of the surface that are unstable or undefined. Right clicking the spin button or edit field will offer a menu of available mesh sizes.
A gradient plot will involve drawing some number of minor polygons with each major polygon where a gradient transition occurs. The total number of polygons that must be rendered in a gradient contour can be quite high, especially when using a 128 color gradient. Gradient plots are thus computationally demanding and rendering performance may suffer when a high mesh count is specified.
100 Spec R->B
100 Spec B->R
128 Spec Rev
Linear (user defined)
Spectral (user defined)
The best way to explore the various gradients is to select them in this option and see how well they serve the visualization desired.
Only the colors within the Linear and Spectral options are adjustable. The Linear option linearly interpolates between the boundary colors based upon their red, green, and blue (RGB) values. The Spec option linearly interpolates between the colors based upon their hue, saturation, and brightness values. To change the color on each bound of the adjustable gradients, click on the color shown to select the color desired.
With the large number of colors present in the gradient contours, it is possible that conflicts will arise with the various colors used in data points and other elements in the graphs. You should use the 2D Graph Customize Colors option to design graph elements that work well with the particular gradient of colors you choose for the contour.
The Reset button restores the program's default 128 Spectrum plot.