+! Copyright (C) 2007, 2008 Alex Chapman
+! See http://factorcode.org/license.txt for BSD license.
+USING: accessors arrays colors combinators float-arrays kernel
+locals math math.constants math.matrices math.order math.ranges
+math.vectors math.quadratic random sequences vectors jamshred.oint ;
+IN: jamshred.tunnel
+
+: n-segments ( -- n ) 5000 ; inline
+
+TUPLE: segment < oint number color radius ;
+C: <segment> segment
+
+: segment-number++ ( segment -- )
+ [ number>> 1+ ] keep (>>number) ;
+
+: random-color ( -- color )
+ { 100 100 100 } [ random 100 / >float ] map first3 1.0 <rgba> ;
+
+: tunnel-segment-distance ( -- n ) 0.4 ;
+: random-rotation-angle ( -- theta ) pi 20 / ;
+
+: random-segment ( previous-segment -- segment )
+ clone dup random-rotation-angle random-turn
+ tunnel-segment-distance over go-forward
+ random-color >>color dup segment-number++ ;
+
+: (random-segments) ( segments n -- segments )
+ dup 0 > [
+ >r dup peek random-segment over push r> 1- (random-segments)
+ ] [ drop ] if ;
+
+: default-segment-radius ( -- r ) 1 ;
+
+: initial-segment ( -- segment )
+ F{ 0 0 0 } F{ 0 0 -1 } F{ 0 1 0 } F{ -1 0 0 }
+ 0 random-color default-segment-radius <segment> ;
+
+: random-segments ( n -- segments )
+ initial-segment 1vector swap (random-segments) ;
+
+: simple-segment ( n -- segment )
+ [ F{ 0 0 -1 } n*v F{ 0 0 -1 } F{ 0 1 0 } F{ -1 0 0 } ] keep
+ random-color default-segment-radius <segment> ;
+
+: simple-segments ( n -- segments )
+ [ simple-segment ] map ;
+
+: <random-tunnel> ( -- segments )
+ n-segments random-segments ;
+
+: <straight-tunnel> ( -- segments )
+ n-segments simple-segments ;
+
+: sub-tunnel ( from to segments -- segments )
+ #! return segments between from and to, after clamping from and to to
+ #! valid values
+ [ sequence-index-range [ clamp-to-range ] curry bi@ ] keep <slice> ;
+
+: nearer-segment ( segment segment oint -- segment )
+ #! return whichever of the two segments is nearer to the oint
+ >r 2dup r> tuck distance >r distance r> < -rot ? ;
+
+: (find-nearest-segment) ( nearest next oint -- nearest ? )
+ #! find the nearest of 'next' and 'nearest' to 'oint', and return
+ #! t if the nearest hasn't changed
+ pick >r nearer-segment dup r> = ;
+
+: find-nearest-segment ( oint segments -- segment )
+ dup first swap rest-slice rot [ (find-nearest-segment) ] curry
+ find 2drop ;
+
+: nearest-segment-forward ( segments oint start -- segment )
+ rot dup length swap <slice> find-nearest-segment ;
+
+: nearest-segment-backward ( segments oint start -- segment )
+ swapd 1+ 0 spin <slice> <reversed> find-nearest-segment ;
+
+: nearest-segment ( segments oint start-segment -- segment )
+ #! find the segment nearest to 'oint', and return it.
+ #! start looking at segment 'start-segment'
+ number>> over >r
+ [ nearest-segment-forward ] 3keep
+ nearest-segment-backward r> nearer-segment ;
+
+: get-segment ( segments n -- segment )
+ over sequence-index-range clamp-to-range swap nth ;
+
+: next-segment ( segments current-segment -- segment )
+ number>> 1+ get-segment ;
+
+: previous-segment ( segments current-segment -- segment )
+ number>> 1- get-segment ;
+
+: heading-segment ( segments current-segment heading -- segment )
+ #! the next segment on the given heading
+ over forward>> v. 0 <=> {
+ { +gt+ [ next-segment ] }
+ { +lt+ [ previous-segment ] }
+ { +eq+ [ nip ] } ! current segment
+ } case ;
+
+:: distance-to-next-segment ( current next location heading -- distance )
+ [let | cf [ current forward>> ] |
+ cf next location>> v. cf location v. - cf heading v. / ] ;
+
+:: distance-to-next-segment-area ( current next location heading -- distance )
+ [let | cf [ current forward>> ]
+ h [ next current half-way-between-oints ] |
+ cf h v. cf location v. - cf heading v. / ] ;
+
+: vector-to-centre ( seg loc -- v )
+ over location>> swap v- swap forward>> proj-perp ;
+
+: distance-from-centre ( seg loc -- distance )
+ vector-to-centre norm ;
+
+: wall-normal ( seg oint -- n )
+ location>> vector-to-centre normalize ;
+
+: distant ( -- n ) 1000 ;
+
+: max-real ( a b -- c )
+ #! sometimes collision-coefficient yields complex roots, so we ignore these (hack)
+ dup real? [
+ over real? [ max ] [ nip ] if
+ ] [
+ drop dup real? [ drop distant ] unless
+ ] if ;
+
+:: collision-coefficient ( v w r -- c )
+ v norm 0 = [
+ distant
+ ] [
+ [let* | a [ v dup v. ]
+ b [ v w v. 2 * ]
+ c [ w dup v. r sq - ] |
+ c b a quadratic max-real ]
+ ] if ;
+
+: sideways-heading ( oint segment -- v )
+ [ forward>> ] bi@ proj-perp ;
+
+: sideways-relative-location ( oint segment -- loc )
+ [ [ location>> ] bi@ v- ] keep forward>> proj-perp ;
+
+: (distance-to-collision) ( oint segment -- distance )
+ [ sideways-heading ] [ sideways-relative-location ]
+ [ nip radius>> ] 2tri collision-coefficient ;
+
+: collision-vector ( oint segment -- v )
+ dupd (distance-to-collision) swap forward>> n*v ;
+
+: bounce-forward ( segment oint -- )
+ [ wall-normal ] [ forward>> swap reflect ] [ (>>forward) ] tri ;
+
+: bounce-left ( segment oint -- )
+ #! must be done after forward
+ [ forward>> vneg ] dip [ left>> swap reflect ]
+ [ forward>> proj-perp normalize ] [ (>>left) ] tri ;
+
+: bounce-up ( segment oint -- )
+ #! must be done after forward and left!
+ nip [ forward>> ] [ left>> cross ] [ (>>up) ] tri ;
+
+: bounce-off-wall ( oint segment -- )
+ swap [ bounce-forward ] [ bounce-left ] [ bounce-up ] 2tri ;
+