Changing the Color Ramp of a 3D Graph Programmatically

[Cavarval]

Overview

This VI is an example of how to modify the Color Ramp of a 3D Graph programmatically in LabVIEW.

Requirements

LabVIEW 2015.

If you need the VI for a previous version either ask in the comments or post in the Version Conversion Forum (probably faster).

Description

The VI generates and plots data on a 3D Surface Graph. Then, it demonstrates how how to modify the Color Ramp settings programmatically using the Surface Color Ramp property from the Graph.

This example is based on the 3D Surface Graph.vi example from LabVIEW and it applies for the following 3D Graph types:

• 3D Contour
• 3D Mesh
• 3D Ribbon
• 3D Scatter
• 3D Stem
• 3D Surface
• 3D Quiver
• 3D Waterfall

To find the example for each 3D Graph type, open the NI Example Finder from LabVIEW going to Help > Find Examples..., select Browse according to Directory Structure and expand Controls and Indicators > Graphs and Charts > Math Plots - 3D.

Note: This example is limited to modifying the color ramp settings from the graph. Note that since the values from the color ramp itself are independent from the axis values, the only way to change the color of the maximum and minimum values from the plotted data, is programmatically defining different Color Ramp Array / Color Ramp Index combinations to adapt to the plotted data limits. There is an example of how to do that attached to the KnowledgeBase 5PJ874JK: How to Set a Fixed Color Ramp in 3D Graph?

Steps to Implement or Execute Code

You just need to run the VI and play around with the Modify Color Ramp control. However, there are a few observations you need to have in mind.

• Changes in the Modify Color Ramp control will not take effect unless Color Ramp Style is set to Custom.
• Color Ramp Array defines the number of steps (colors) in the ramp.
• Color Ramp Index defines the color transition positions. The number of elements in Color Ramp Index will be N-1, where N is the number of elements in Color Ramp Array.
• The index values from the Color Ramp Index array are relative positions. An index of 0 corresponds to the position of the minimum value in the graph data and an index of 255 corresponds to the position of the maximum value. Consequently, an index of 127 will correspond to the middle value. These position values are 100% independent from the axis scale values.
• The element i from the Color Ramp Array corresponds to element i-1 from the Color Ramp Index (the misalignment in the arrays is intentional). The index value from the first element in Color Ramp Array is 0 and cannot be changed.
• To increase or decrease the number of colors you just need to add or delete elements in both arrays.

The Modify Color Ramp control does not include the Logarithm? element from the property. If you try to change this setting from the front panel of a VI simply using the value from the Surface Color Ramp property you will either see no change or have an undesired result. This happens becsue since the 3D Graph is an XControl, whenever the Logarithm? setting is changed on the 3D Plot Properties > Surface > (Color Ramp) Edit window, the graph processes the change and updates the values from all the elements in Color Ramp Index in a logarithmic way, but if you just send a True value to the element through the property, this does not happen. This VI however, allows changing the graph both in the Front Panel or in the 3D Plot Properties window without conflict (see note in the Block Diagram).

Block Diagram of the VI