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TITLE           Topology shader

OCCURRENCE      ARB_NT/Tree/Tree shading/Topology shader

DESCRIPTION     This shader uses the tree currently displayed in the main
                tree display as a reference to shade species.

                Species at the top of that tree will be shaded with the "low" color,
                species at the bottom with the "high" color of the active color-range.

                The intented purpose of this shader is comparing two tree topologies.
                To do that, display one of the trees in the main window, then open a
                second treeview using "File/New Window" and display a different tree
                in that window.

                  * The tree in the main window will always be shaded continuously.

                  * Shading of trees in other windows will be non-continuous where their
                    topology differs from the topology shown in the main window.
                    This facilitates the detection of topology differences.

                The granularity of topology shading depends on the size of the reference tree.
                Therefore modifying the settings in section 'Value phasing' is strongly
                recommended while comparing topologies:

                  * to detect local topology differences, increase the phasing frequency
                    until adjacent species are displayed in distinguishable colors.
                    Then use either of the phase-shift sliders to shift the shading.
                  * to detect global topology differences, decrease the phasing frequency.

NOTES           Whenever the tree in the main tree display changes, the shading is instantly
                updated and refreshed in all tree displays.

                You can use the logical zoom-mode in the main tree display while the
                topology shader is active, to shade only the zoomed part of the tree.

EXAMPLES        The range allowed for the phasing frequency is [0.01 .. 100].
                The number of colors available for shading is currently limited to 4096.

                When you compare trees with e.g. 500k Species,

                  * using a frequency of 1.0 will shade approx. 120 adjacent species with the same color,
                  * using a frequency of 0.1 will shade approx. 1200 adjacent species with the same color and
                  * using a frequency of 10 will shade approx. 12 adjacent species with the same color.

WARNINGS        This feature will cause frequent display updates. Using it while ARB is running
                over a remote connection may be dissatisfying.

BUGS            No bugs known