From b973df588b129467bc81fa633ab4173de7f0d408 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miloslav=20=C4=8C=C3=AD=C5=BE?= <tastyfish@seznam.cz>
Date: Thu, 23 Aug 2018 09:25:34 +0200
Subject: [PATCH] Add sin and cos

---
 raycastlib.h | 35 ++++++++++++++++++++++++++++++++++-
 test.c       | 16 ++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/raycastlib.h b/raycastlib.h
index dd178ad..4aa24ee 100644
--- a/raycastlib.h
+++ b/raycastlib.h
@@ -11,7 +11,6 @@
   - X axis goes right.
   - Y axis goes up.
   - Each game square is UNITS_PER_SQUARE * UNITS_PER_SQUARE.
-
   */
 
 #define UNITS_PER_SQUARE 1024
@@ -84,6 +83,11 @@ void castRayMultiHit(Ray ray, int16_t (*arrayFunc)(int16_t, int16_t),
   uint16_t maxSteps, HitResult *hitResults, uint16_t *hitResultsLen,
   uint16_t maxHits);
 
+Unit cosInt(Unit input);
+Unit sinInt(Unit input);
+uint16_t sqrtInt(uint32_t value);
+Unit dist(Vector2D p1, Vector2D p2);
+
 //=============================================================================
 // privates
 
@@ -98,6 +102,35 @@ Unit clamp(Unit value, Unit valueMin, Unit valueMax)
   return value;
 }
 
+// Bhaskara's cosine approximation formula
+#define trigHelper(x) (UNITS_PER_SQUARE *\
+  (UNITS_PER_SQUARE / 2 * UNITS_PER_SQUARE / 2 - 4 * (x) * (x)) /\
+  (UNITS_PER_SQUARE / 2 * UNITS_PER_SQUARE / 2 + (x) * (x)))
+
+Unit cosInt(Unit input)
+{
+  input = input % UNITS_PER_SQUARE;
+
+  if (input < 0)
+    input = UNITS_PER_SQUARE + input;
+
+  if (input < UNITS_PER_SQUARE / 4)
+    return trigHelper(input);
+  else if (input < UNITS_PER_SQUARE / 2)
+    return -1 * trigHelper(UNITS_PER_SQUARE / 2 - input);
+  else if (input < 3 * UNITS_PER_SQUARE / 4)
+    return -1 * trigHelper(input - UNITS_PER_SQUARE / 2);
+  else
+    return trigHelper(UNITS_PER_SQUARE - input);
+}
+
+#undef trigHelper
+
+Unit sinInt(Unit input)
+{
+  return cosInt(input - UNITS_PER_SQUARE / 2);
+}
+
 uint16_t sqrtInt(uint32_t value)
 {
   uint32_t result = 0;
diff --git a/test.c b/test.c
index dfcecc2..e64b6e5 100644
--- a/test.c
+++ b/test.c
@@ -1,3 +1,9 @@
+/**
+  Tests for raycastlib.
+
+  license: CC0
+*/
+
 #include <stdio.h>
 #include "raycastlib.h"
 
@@ -70,5 +76,15 @@ int main()
     16))
     return 1; 
 
+  for (Unit i = -UNITS_PER_SQUARE; i <= UNITS_PER_SQUARE; i += 64)
+  {
+    Unit v = sinInt(i);
+
+    for (int j = 0; j < (v + UNITS_PER_SQUARE) / 64; ++j)
+      printf(".");
+
+    printf("\n");
+  }
+
   return 0;
 }