Pierre did an excellent work on having gradient lines.

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| v elem1 elem2 edge |
v := RTView new.

elem1 := (RTEllipse new color: (Color blue alpha:0.3); size:20) elementOn: 1.
elem2 := (RTEllipse new color: (Color red alpha:0.9); size:20) elementOn: 2.
elem2 translateBy: 300@0.
v add: elem1.
v add: elem2.

edge := RTEdge from:elem1 to:elem2.
v add: (edge + (RTGradientColoredLine new colors: (Array with: (elem1 color) with: (elem2 color)); precision: 100; gradientColorShape)).
v open

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| v elem1 elem2 edge |
v := RTView new.

elem1 := (RTEllipse new color: (Color red alpha:0.3); size:20) elementOn: 1.
elem2 := (RTEllipse new color: (Color red alpha:0.9); size:20) elementOn: 2.
elem2 translateBy: 300@0.
v add: elem1.
v add: elem2.

edge := RTEdge from:elem1 to:elem2.
v add: (edge + (RTGradientColoredLine new colors: (Array with: (elem1 color) with: (elem2 color)); precision: 100; gradientColorShape)).
v open

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Feedback are welcomed!

Pierre & Alexandre