This shows the sort of thing I want.
you can achieve this with the original FluxusMain.cpp. you just have to
simulate what fluxus does. don't use the (blur) command, don't clear the
screen. when everything is drawn set the blend mode and draw a
transparent plane over the screen using the clear colour and the blur
value for opacity.
(require racket/math)
(clear)
(clear-frame 0)
(colour (vector 0.2 0.03 0.015))
(blend-mode 'one 'one)
(define aplane (build-plane))
(every-frame
(begin
(with-primitive aplane
(identity)
(let ([t (* 0.4 (time))])
(translate (vector (sin t) (cos t) 7.7))
(rotate (vector 0 0 (/ (* 360 t) pi)))))
(with-state
(blend-mode 'src-alpha 'one-minus-src-alpha)
(scale (vector 20 16 1))
(colour (vector 0 0 0.01 0.005))
(draw-plane))))
best,
gabor