5c1a3615e9fc

--- a/package.lisp	Sun Apr 10 23:13:35 2016 +0000
+++ b/package.lisp	Tue Apr 12 22:05:57 2016 +0000
@@ -7,4 +7,6 @@
   (:use #:cl
         #:sketch
         #:coding-math.quickutils
-        #:coding-math.utils))
+        #:coding-math.utils)
+  (:shadow
+    #:normalize))

--- a/src/main.lisp	Sun Apr 10 23:13:35 2016 +0000
+++ b/src/main.lisp	Tue Apr 12 22:05:57 2016 +0000
@@ -47,7 +47,7 @@
     (rotate (degrees angle))
     (when thrustingp
       (with-pen (make-pen :fill (rgb 1.0 0.0 0.0))
-        (ngon 3 -15 0 10 6))) ; fire 
+        (ngon 3 -15 0 10 6))) ; fire
     (with-pen (make-pen :stroke (gray 0) :fill (gray 0.5))
       (rect -10 -3 10 6) ; engine
       (ngon 3 0 0 10 10) ; hull
@@ -60,22 +60,13 @@
     ((mx 0)
      (my 0)
      (frame 1)
-     (sun (make-particle center-x center-y
-                         :mass 2000.0))
-     (planet (make-particle (+ center-x 200) center-y
-                            :speed 3.0
-                            :direction (- (/ tau 4))
-                            ))
      )
   (background (gray 1))
   (incf frame)
   ;;
-  (particle-gravitate-to! planet sun)
-  (particle-update! planet)
-  (with-pen (make-pen :stroke (gray 0) :fill (rgb 1.0 1.0 0.0))
-    (circle (particle-x sun) (particle-y sun) 50))
   (with-pen (make-pen :stroke (gray 0) :fill (rgb 0.0 1.0 0.0))
-    (circle (particle-x planet) (particle-y planet) 10))
+    (circle center-x center-y
+            (map-range 0 *height* 5 100 my)))
   ;;
   (when (zerop (mod frame 20))
     (calc-fps 20))
@@ -83,7 +74,7 @@
 
 
 ;;;; Mouse
-(defmethod mousemotion-event ((window cm) ts b x y xrel yrel)
+(defmethod kit.sdl2:mousemotion-event ((window cm) ts b x y xrel yrel)
   (declare (ignore ts b xrel yrel))
   (with-slots (mx my) window
     (setf mx x)

--- a/src/math.lisp	Sun Apr 10 23:13:35 2016 +0000
+++ b/src/math.lisp	Tue Apr 12 22:05:57 2016 +0000
@@ -1,14 +1,35 @@
 (in-package #:coding-math)
 
+;; Constants
 (defconstant tau (* pi 2))
 
 
-(defun normalize (n min max)
-  (/ (- n min)
+;; Number range mapping
+(defun normalize (min max val)
+  (/ (- val min)
      (- max min)))
 
+(defun lerp (from to n)
+  "Lerp together `from` and `to` by factor `n`.
 
-(defun lerp (from to n)
+  Note that you might want `precise-lerp` instead.
+
+  "
   (+ from
      (* n (- to from))))
 
+(defun precise-lerp (from to n)
+  "Lerp together `from` and `to` by factor `n`, precisely.
+
+  Vanilla lerp does not guarantee `(lerp from to 0.0)` will return exactly
+  `from` due to floating-point errors.  This version will return exactly `from`
+  when given a `n` of `0.0`, at the cost of an extra multiplication.
+
+  "
+  (+ (* (- 1 n) from)
+     (* n to)))
+
+(defun map-range (source-from source-to dest-from dest-to source-val)
+  "Map `source-val` from the source range to the destination range."
+  (lerp dest-from dest-to
+        (normalize source-from source-to source-val)))