partially done work on total source tree rework, separation of engine context and game context, generalization of renderer for different backends as well as web platform target

src/twn_camera.c

@@ -0,0 +1,52 @@
+#include "twn_camera.h"
+#include "twn_context.h"
+
+#include <math.h>
+
+
+#define CAMERA_NEAR_Z 0.1f
+#define CAMERA_FAR_Z 100.0f
+
+
+t_matrix4 camera_look_at(const t_camera *const camera) {
+    /* from cglm */
+    const t_fvec3 r = m_vec_norm(m_vec_cross(camera->target, camera->up));
+    const t_fvec3 u = m_vec_cross(r, camera->target);
+
+    t_matrix4 result;
+
+    result.row[0].x =  r.x;
+    result.row[0].y =  u.x;
+    result.row[0].z = -camera->target.x;
+    result.row[1].x =  r.y;
+    result.row[1].y =  u.y;
+    result.row[1].z = -camera->target.y;
+    result.row[2].x =  r.z;
+    result.row[2].y =  u.z;
+    result.row[2].z = -camera->target.z;
+    result.row[3].x = -m_vec_dot(r, camera->pos);
+    result.row[3].y = -m_vec_dot(u, camera->pos);
+    result.row[3].z =  m_vec_dot(camera->target, camera->pos);
+    result.row[0].w =  result.row[1].w = result.row[2].w = 0.0f;
+    result.row[3].w =  1.0f;
+
+    return result;
+}
+
+t_matrix4 camera_perspective(const t_camera *const camera) {
+    /* from cglm */
+    t_matrix4 result = {0};
+
+    const float aspect = RENDER_BASE_RATIO;
+
+    const float f  = 1.0f / tanf(camera->fov * 0.5f);
+    const float fn = 1.0f / (CAMERA_NEAR_Z - CAMERA_FAR_Z);
+
+    result.row[0].x =  f / aspect;
+    result.row[1].y =  f;
+    result.row[2].z =  (CAMERA_NEAR_Z + CAMERA_FAR_Z) * fn;
+    result.row[2].w = -1.0f;
+    result.row[3].z =  2.0f * CAMERA_NEAR_Z * CAMERA_FAR_Z * fn;
+
+    return result;
+}