lovr.math.orientationToDirection;

src/api/math.c

@@ -54,6 +54,19 @@ int l_lovrMathLookAt(lua_State* L) {
   return 4;
 }
 
+int l_lovrMathOrientationToDirection(lua_State* L) {
+  float angle = luaL_checknumber(L, 1);
+  float ax = luaL_optnumber(L, 2, 0);
+  float ay = luaL_optnumber(L, 3, 1);
+  float az = luaL_optnumber(L, 4, 0);
+  float v[3];
+  lovrMathOrientationToDirection(angle, ax, ay, az, v);
+  lua_pushnumber(L, v[0]);
+  lua_pushnumber(L, v[1]);
+  lua_pushnumber(L, v[2]);
+  return 3;
+}
+
 int l_lovrMathRandom(lua_State* L) {
   luax_pushtype(L, RandomGenerator, lovrMathGetRandomGenerator());
   lua_insert(L, 1);
@@ -81,6 +94,7 @@ int l_lovrMathSetRandomSeed(lua_State* L) {
 const luaL_Reg lovrMath[] = {
   { "newRandomGenerator", l_lovrMathNewRandomGenerator },
   { "newTransform", l_lovrMathNewTransform },
+  { "orientationToDirection", l_lovrMathOrientationToDirection },
   { "lookAt", l_lovrMathLookAt },
   { "random", l_lovrMathRandom },
   { "randomNormal", l_lovrMathRandomNormal },

src/math/math.c

@@ -1,4 +1,6 @@
 #include "math.h"
+#include "math/vec3.h"
+#include <math.h>
 #include <stdlib.h>
 #include <time.h>
 
@@ -18,3 +20,11 @@ void lovrMathDestroy() {
 RandomGenerator* lovrMathGetRandomGenerator() {
   return generator;
 }
+
+void lovrMathOrientationToDirection(float angle, float ax, float ay, float az, vec3 v) {
+  float sinTheta = sin(angle);
+  float cosTheta = cos(angle);
+  v[0] = sinTheta * -ay + (1 - cosTheta) * -az * ax;
+  v[1] = sinTheta * ax + (1 - cosTheta) * -az * ay;
+  v[2] = -cosTheta + (1 - cosTheta) * -az * az;
+}

src/math/math.h

@@ -14,3 +14,4 @@ typedef vec_t(mat4) vec_mat4_t;
 void lovrMathInit();
 void lovrMathDestroy();
 RandomGenerator* lovrMathGetRandomGenerator();
+void lovrMathOrientationToDirection(float angle, float ax, float ay, float az, vec3 v);