In case did you see we have a manual:
” After application of RE:Flex Warp, each pair of successive splines specify a “from” geometry and a “to” geometry correspondence. The first of a pair is the “from” geometry and the second of the pair is the corresponding “to” geometry ”
Manual lives here:
combustion 4\Plugins\REVisionEffects\REFlex\REFlexManual\REFlex3ManualCombustion.htm
RE:Flex Warp and Motion Morph require you think in terms of you have one source spline and one destination spline. For warp
1) Apply Operator
2) In Workspace view click on Operator so that a grey rectangle shows up beside it
3) Set Control Display to UnWarp Image
4) Switch to toolbar view and select the spline drawing icon
5) Draw a spline
6) then one way to do it simply is just to select Polygon in the Timeline view and CTRL-ALT-D duplicate each time you add a spline. So now you have Polygon 2.
7) Check AutoHide Splines
8) Move the spline vertices
9) Now change between Warped and Unwarped view and you should see the two splines are in different position, when in Warped view the image is warped
If something is still unclear ask again
Pierre