3D Colormaps

Applies to: 3D and Studio.

Two colormaps, RYC 3-zone and CYR 3-zone, replaced two older narrow-hue ramps (Dark Red to Light Red to Magenta, and Dark Blue to Light Blue to Magenta) in 2026. The old ramps worked well enough over a shaded surface, where the shading carries the shape and the colour only has to stay out of the way -- but as a gradient, where colour is the only channel carrying z, a map that spends its whole length inside one hue family says almost nothing: a reader can see that one region is lighter than another and cannot say by how much or where a boundary lies.

What a Zone Map Is

TableCurve has offered RYGC 4-zone and CGYR 4-zone for many years, and RYC and CYR are built the same way, with three bands instead of four. Each band is a full dark-to-bright ramp in one hue, and the hue changes abruptly at the band boundary -- that discontinuity is the entire point.

A ramp answers "how much?". A zone map answers "which band?". The eye reads a hue change instantly and without a legend; it reads a lightness change slowly and only by comparison. A zone map converts the z axis from a quantity into a classification, at the boundaries you choose rather than the ones the data happens to produce.

Zone maps suit:

·    A surface where the real question is which region is above threshold.

·    A residual or confidence surface where the levels have an agreed meaning.

·    Any map where you would otherwise draw contour lines at three or four fixed values.

Three Zones, Not Only Four

The common probability bounds are 90/95/99, so three regimes is the more frequent question than four. Four bands ask the reader to hold four boundaries in mind; three map onto the interval structure that statistical work actually uses. RYGC was never wrong -- it was simply the only zone map available, so it got used for three-regime questions too, with one band doing nothing.

RYC and CYR: a Pair, Not Two Options

RYC runs red to yellow to cyan; CYR runs cyan to yellow to red. They are the same map in opposite directions, exactly as RYGC and CGYR are -- and the direction decides which end of z is the alarming one:

·    RYC -- red at the bottom. Use it when low z is the bad news: a coverage surface, a yield, a goodness statistic.

·    CYR -- red at the top. Use it when high z is the bad news: a residual magnitude, an error, a cost.

Using Them

RYC and CYR are ordinary view types. They appear in the 3D Graph Type dialog's left column with the other TableCurve maps, they work as a gradient and as a contour palette, and nothing about them is special-cased.

The bands are equal width in z, always -- they divide the rendered z range into three equal parts. They do not know where 90/95/99 fall in your data. Three bands is the useful count for that kind of question; the boundaries are not computed from a probability. If the boundaries must land on particular values, set the z range so they do.