Add movement relative to time

Previously movement was based on frames rather than
time. I added time_get_dt() function for getting time
since last frame and changed rotation speed to use this
function.

Signed-off-by: Piotr Krygier <piotrkrygier@everyonecancode@xyz>

graphics/src/rse_graphics.c

@@ -28,7 +28,6 @@ struct rse_graphics_context_t
     struct graphics_context_t* context;
 };
 
-#define NS_TO_S(time) (time/1000000000)
 static void model_view_projection_update(struct graphics_context_t* context)
 {
     vec3 eye = {0};
@@ -38,6 +37,7 @@ static void model_view_projection_update(struct graphics_context_t* context)
     float fovy;
     float z_near;
     float z_far;
+    static float rotation = 0.0;
 
     eye[2] = -5.0f;
 
@@ -49,7 +49,7 @@ static void model_view_projection_update(struct graphics_context_t* context)
 
     glm_mat4_identity(context->mvp_data.model);
 
-    glm_rotate(context->mvp_data.model, time_get_sec_from_start() * glm_rad(90.0f), rotation_vec);
+    glm_rotate(context->mvp_data.model, rotation, rotation_vec);
     glm_lookat(eye, center, up, context->mvp_data.view);
     glm_perspective(
         fovy,
@@ -57,6 +57,8 @@ static void model_view_projection_update(struct graphics_context_t* context)
         z_near,
         z_far,
         context->mvp_data.proj);
+
+    rotation += time_get_dt() * glm_rad(90.0);
 }
 
 static rse_err_t render_static_mesh(struct graphics_context_t* context, uint32_t renderer_id)

graphics/src/window.c

@@ -70,6 +70,7 @@ rse_err_t window_loop(struct graphics_context_t* context)
             }
         }
 
+        time_update();
         draw_frame(context);
         fps_print(&start_time);
     }

red_scarf_engine/meson.build

@@ -14,5 +14,8 @@ executable(
   dependencies : [
                   sdl3_dep,
                   ],
-  link_with: rse_graphics_lib,
+  link_with: [
+            rse_graphics_lib,
+            rse_utilities_lib,
+            ],
   )

red_scarf_engine/src/main.c

@@ -3,6 +3,7 @@
 #include "graphics/rse_graphics.h"
 #include "utilities/errors_common.h"
 #include "SDL3/SDL_thread.h"
+#include "utilities/time_utils.h"
 
 
 int main(int argc, char** argv)
@@ -15,6 +16,7 @@ int main(int argc, char** argv)
 
     SDL_SetLogPriorities(SDL_LOG_PRIORITY_VERBOSE);
 
+    STATUS_CHECK(time_init());
     STATUS_CHECK(rse_graphics_init(&context));
     STATUS_CHECK(rse_graphics_test_function(context));
 

utilities/src/time_utils.c

@@ -1,9 +1,33 @@
 #include "time_utils.h"
 #include <stdint.h>
 #include "SDL3/SDL_timer.h"
+#include "commons.h"
+#include "errors_common.h"
 
 #define NS_TO_S(time) (time/1000000000)
+double g_last_time = 0.0;
+
+rse_err_t time_init(void)
+{
+    g_last_time = NS_TO_S((double)SDL_GetTicksNS());
+
+    return RSE_ERROR_NO_ERROR;
+}
+
 double time_get_sec_from_start(void)
 {
     return NS_TO_S((double)SDL_GetTicksNS());
 }
+
+void time_update(void)
+{
+    g_last_time = NS_TO_S((double)SDL_GetTicksNS());
+}
+
+double time_get_dt(void)
+{
+    float time = NS_TO_S((double)SDL_GetTicksNS());
+    float dt = time - g_last_time;
+
+    return dt;
+}

utilities/time_utils.h

@@ -12,6 +12,13 @@
 #ifndef TIME_UTILS_H_
 #define TIME_UTILS_H_
 
+#include "commons.h"
+
+rse_err_t time_init(void);
+void time_update(void);
+
 double time_get_sec_from_start(void);
 
+double time_get_dt(void);
+
 #endif // !TIME_UTILS_H_