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| -rw-r--r-- | doc/api.texi | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/doc/api.texi b/doc/api.texi index 79b6dbd..47e16f5 100644 --- a/doc/api.texi +++ b/doc/api.texi @@ -366,6 +366,7 @@ detection. * Matrices:: Transformation matrices. * Quaternions:: Rotations about an arbitrary axis. * Easings:: Easing functions for interesting animations. +* Bezier Curves:: Cubic Bezier curves and paths in 2D space. @end menu @node Basics @@ -1016,6 +1017,66 @@ Return the identity quaternion. @deffn {Procedure} ease-in-out-sine @var{t} @end deffn +@node Bezier Curves +@subsection Bezier Curves + +The @code{(chickadee math bezier)} module provides an API for +describing cubic Bezier curves in 2D space. These curves are notably +used in font description, vector graphics programs, and when it comes +to games: path building. With Bezier curves, it's somewhat easy to +create a smooth looking path for an enemy to move along, for example. +Bezier curves become particularly interesting when they are chained +together to form a Bezier ``path'', where the end point of one curve +becomes the starting point of the next. + +Currently, the rendering of Bezier curves is rather crude and provided +mostly for visualizing and debugging curves that would be unseen in +the final game. See @xref{Lines and Shapes} for more information. + +@deffn {Procedure} make-bezier-curve @var{p0} @var{p1} @var{p2} @var{p3} +Return a new Bezier curve object whose starting point is @var{p0}, +ending point is @var{p3}, and control points are @var{p1} and +@var{p2}. All points are 2D vectors. +@end deffn + +@deffn {Procedure} bezier-curve? @var{obj} +Return @code{#t} if @var{obj} is a Bezier curve. +@end deffn + +@deffn {Procedure} bezier-curve-p0 @var{bezier} +Return the starting point of @var{bezier}. +@end deffn + +@deffn {Procedure} bezier-curve-p1 @var{bezier} +Return the first control point of @var{bezier}. +@end deffn + +@deffn {Procedure} bezier-curve-p2 @var{bezier} +Return the second control point of @var{bezier}. +@end deffn + +@deffn {Procedure} bezier-curve-p3 @var{bezier} +Return the end point of @var{bezier}. +@end deffn + +@deffn {Procedure} bezier-path . @var{control-points} +Return a list of connected bezier curves defined by +@var{control-points}. The first curve is defined by the first 4 +arguments and every additional curve thereafter requires 3 additional +arguments. +@end deffn + +@deffn {Procedure} bezier-curve-point-at @var{bezier} @var{t} +Return the coordinates for @var{bezier} at @var{t} (a value in the +range [0, 1] representing how far from the start of the curve to +check) as a 2D vector. +@end deffn + +@deffn {Procedure} bezier-curve-point-at! @var{dest} @var{bezier} @var{t} +Modify the 2D vector @var{dest} in-place to contain the coordinates +for @var{bezier} at @var{t}. +@end deffn + @node Graphics @section Graphics @@ -1297,6 +1358,42 @@ the @var{shader} argument to override the built-in line segment shader. @end deffn +@deffn {Procedure} draw-bezier-curve @var{bezier} [#:segments 32] @ + [#:control-points?] [#:tangents?] @ + [#:control-point-size 8] @ + [#:control-point-color yellow] @ + [#:tangent-color yellow] @ + [#:thickness 0.5] [#:feather 1.0] @ + [#:matrix] + +Draw the curve defined by @var{bezier} using a resolution of N +@var{segments}. When @var{control-points?} is @code{#t}, the control +points are rendered as squares of size @var{control-point-size} pixels +and a color of @var{control-point-color}. When @var{tangents?} is +@code{#t}, the tangent lines from terminal point to control point are +rendered using the color @var{tangent-color}. + +All line segments rendered use @code{draw-line}, and thus the +arguments @var{thickness} and @var{feather} have the same effect as in +that procedure. + +A custom @var{matrix} may be passed for applications that require more +control over the final output. +@end deffn + +@deffn {Procedure} draw-bezier-path @var{path} [#:segments 32] @ + [#:control-points?] [#:tangents?] @ + [#:control-point-size 8] @ + [#:control-point-color yellow] @ + [#:tangent-color yellow] @ + [#:thickness 0.5] [#:feather 1.0] @ + [#:matrix] + +Render @var{path}, a list of bezier curves. See the documentation for +@code{draw-bezier-curve} for an explanation of all the keyword +arguments. +@end deffn + @node Fonts @subsection Fonts |