extract fovy and aspect for perpective matrix

include/cglm/cam.h

@@ -426,6 +426,31 @@ glm_persp_decomp_near(mat4 proj, float * __restrict nearVal) {
   *nearVal = proj[3][2] / (proj[2][2] - 1);
 }
 
+/*!
+ * @brief returns field of view angle along the Y-axis (in radians)
+ *
+ * if you need to degrees, use glm_deg to convert it or use this:
+ * fovy_deg = glm_deg(glm_persp_fovy(projMatrix))
+ *
+ * @param[in] proj perspective projection matrix
+ */
+CGLM_INLINE
+float
+glm_persp_fovy(mat4 proj) {
+  return 2.0 * atan(1.0 / proj[1][1]);
+}
+
+/*!
+ * @brief returns aspect ratio of perspective projection
+ *
+ * @param[in] proj perspective projection matrix
+ */
+CGLM_INLINE
+float
+glm_persp_aspect(mat4 proj) {
+  return proj[1][1] / proj[0][0];
+}
+
 /*!
  * @brief extracts view frustum planes
  *

makefile.am

@@ -93,7 +93,8 @@ libcglm_la_SOURCES=\
 test_tests_SOURCES=\
     test/src/test_common.c \
     test/src/test_main.c \
-    test/src/test_mat4.c
+    test/src/test_mat4.c \
+    test/src/test_cam.c
 
 all-local:
 	sh ./post-build.sh

test/src/test_cam.c

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c), Recep Aslantas.
+ *
+ * MIT License (MIT), http://opensource.org/licenses/MIT
+ * Full license can be found in the LICENSE file
+ */
+
+#include "test_common.h"
+
+void
+test_camera_decomp(void **state) {
+  mat4  proj;
+  float aspect, fovy, nearVal, farVal;
+
+  aspect  = 0.782f;
+  fovy    = glm_rad(49.984f);
+  nearVal = 0.1f;
+  farVal  = 100.0f;
+
+  glm_perspective(fovy, aspect, nearVal, farVal, proj);
+  assert_true(fabsf(aspect  - glm_persp_aspect(proj)) < FLT_EPSILON);
+  assert_true(fabsf(fovy    - glm_persp_fovy(proj))   < FLT_EPSILON);
+  assert_true(fabsf(49.984f - glm_deg(glm_persp_fovy(proj))) < FLT_EPSILON);
+}
+

test/src/test_main.c

@@ -11,6 +11,9 @@ main(int argc, const char * argv[]) {
   const struct CMUnitTest tests[] = {
     /* mat4 */
     cmocka_unit_test(test_mat4),
+
+    /* camera */
+    cmocka_unit_test(test_camera_decomp)
   };
 
   return cmocka_run_group_tests(tests,

test/src/test_tests.h

@@ -9,4 +9,8 @@
 /* mat4 */
 void test_mat4(void **state);
 
+/* camera */
+void
+test_camera_decomp(void **state);
+
 #endif /* test_tests_h */