From 6635fdd7c1e612ebc858f4c275dd9986b6cd441d Mon Sep 17 00:00:00 2001
From: Recep Aslantas <info@recp.me>
Date: Sun, 11 Sep 2016 23:11:24 +0300
Subject: [PATCH] lookat

---
 include/cglm-cam.h | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 include/cglm-vec.h | 25 ++++++++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 include/cglm-cam.h

diff --git a/include/cglm-cam.h b/include/cglm-cam.h
new file mode 100644
index 0000000..58403cd
--- /dev/null
+++ b/include/cglm-cam.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c), Recep Aslantas.
+ *
+ * MIT License (MIT), http://opensource.org/licenses/MIT
+ * Full license can be found in the LICENSE file
+ */
+
+#ifndef glm_vcam_h
+#define glm_vcam_h
+
+#include "cglm.h"
+
+CGLM_INLINE
+void
+glm_lookat(vec3 eye,
+           vec3 center,
+           vec3 up,
+           mat4 dest) {
+  vec3 f, u, s;
+
+  glm_vec_sub3(center, eye, f);
+  glm_vec_normalize_self(f);
+
+  glm_vec_cross(f, up, s);
+  glm_vec_normalize_self(s);
+
+  glm_vec_cross(s, f, u);
+
+  dest[0][0] = s[0];
+  dest[1][0] = s[1];
+  dest[2][0] = s[2];
+  dest[0][1] = u[0];
+  dest[1][1] = u[1];
+  dest[2][1] = u[2];
+  dest[0][2] =-f[0];
+  dest[1][2] =-f[1];
+  dest[2][2] =-f[2];
+  dest[3][0] =-glm_vec_dot(s, eye);
+  dest[3][1] =-glm_vec_dot(u, eye);
+  dest[3][2] = glm_vec_dot(f, eye);
+  dest[0][3] = 0;
+  dest[1][3] = 0;
+  dest[2][3] = 0;
+  dest[3][3] = 1;
+}
+
+#endif /* glm_vcam_h */
diff --git a/include/cglm-vec.h b/include/cglm-vec.h
index 38e68f3..2d79361 100644
--- a/include/cglm-vec.h
+++ b/include/cglm-vec.h
@@ -54,4 +54,29 @@ glm_vec_normalize(vec3 vec, vec3 dest) {
   dest[2] = vec[2] / norm;
 }
 
+CGLM_INLINE
+void
+glm_vec_normalize_self(vec3 v) {
+  float norm;
+
+  norm = glm_vec_norm(v);
+
+  if (norm == 0.0f) {
+    v[0] = v[1] = v[2] = 0.0f;
+    return;
+  }
+
+  v[0] = v[0] / norm;
+  v[1] = v[1] / norm;
+  v[2] = v[2] / norm;
+}
+
+CGLM_INLINE
+void
+glm_vec_sub3(vec3 v1, vec3 v2, vec3 dest) {
+  dest[0] = v1[0] - v2[0];
+  dest[1] = v1[1] - v2[1];
+  dest[2] = v1[2] - v2[2];
+}
+
 #endif /* cglm_vec_h */