order-index-knot-constants ( curve order index -- knot-constants )

Vocabulary

nurbs

Inputs

curve	an object
order	an object
index	an object

Outputs

knot-constants

an object

Definition

USING: accessors math sequences
specialized-arrays.instances.alien.c-types.float ;

IN: nurbs

:: order-index-knot-constants
    ( curve order index -- knot-constants )
    curve knots>> :> knots index order 1 - + knots nth
    :> knot_i+k-1 index knots nth :> knot_i index order +
    knots nth :> knot_i+k index 1 + knots nth
    :> knot_i+1 knot_i+k-1 knot_i -
    ?recip :> c1 knot_i+1 knot_i+k - ?recip :> c2 knot_i c1 *
    neg :> c3 knot_i+k c2 * neg :> c4 c1 c2 c3 c4
    float-array{ } 4sequence ;