a-game

commit 931610c121c6bc87d5cd6e58f514975f6fd46acf
parent d4de91463dc441cd190bff9b2f0006429459b58f
Author: amin <dev@aminmesbah.com>
Date:   Tue, 16 Apr 2019 17:59:01 +0000

Define player speed in terms of meters per second

FossilOrigin-Name: 0b6ff424630a4657585aedc40d92986bc2a016309079cb022c6431d676c56a89
Diffstat:
M
src/game.c
 | 
9
++++++---
M
src/platform_linux.c
 | 
30
++++++++++++++++++++----------
M
src/platform_linux.h
 | 
6
------

3 files changed, 26 insertions(+), 19 deletions(-)
diff --git a/src/game.c b/src/game.c
@@ -93,10 +93,12 @@ void game_init(struct GameState *game_state, v2u framebuffer)
 }
 
 
+// NOTE(amin): For now updating and rendering are interleaved. We simulate the
+// world at the same rate we render it. Our timestep is not fixed. We may want
+// to change this in the future.
 void game_update_and_render(struct GameState *game_state, f32 dt, v2u framebuffer)
 {
-    rect viewport;
-
+    rect viewport = {0};
     f32 ppm = 0.0f;
     {
         f32 screen_aspect_ratio = (f32)framebuffer.width / (f32)framebuffer.height;
@@ -188,7 +190,8 @@ void game_update_and_render(struct GameState *game_state, f32 dt, v2u framebuffe
 
     // update player
     {
-        f32 movement_speed = 0.2f;
+        f32 max_meters_per_second = 5.0f;
+        f32 movement_speed = max_meters_per_second * dt;
         struct GameInput input = game_state->input;
 
         if (input.key_up)
diff --git a/src/platform_linux.c b/src/platform_linux.c
@@ -69,23 +69,30 @@ int main(void)
 
     struct GameState game_state = {0};
     glfwSetWindowUserPointer(window, &game_state);
-    game_init(&game_state, glmth_v2u_init(PLATFORM_SCR_WIDTH, PLATFORM_SCR_HEIGHT));
+    game_init(&game_state, (v2u) {PLATFORM_SCR_WIDTH, PLATFORM_SCR_HEIGHT});
 
 #ifdef PLATFORM_HOTLOAD_GAME_CODE
     struct GameCode game_code = load_game_code(PLATFORM_GAME_LIB_PATH);
     game_code.game_load_opengl_symbols();
 #endif
 
-    uint64_t lag = 0;
-    uint64_t previous_ms = (glfwGetTimerValue() * PLATFORM_SECOND) / glfwGetTimerFrequency();
+    // NOTE(amin): lag should always be very small, so it's fine to use a float
+    // to store it. We will not run out of precision.
+    uint64_t previous_wall_clock_time = glfwGetTimerValue();
+    uint64_t timer_frequency = glfwGetTimerFrequency();
+    float dt = 0.0f;
 
     while (!glfwWindowShouldClose(window))
     {
-        uint64_t current_ms = (glfwGetTimerValue() * PLATFORM_SECOND) / glfwGetTimerFrequency();
-        uint64_t elapsed_ms = current_ms - previous_ms;
-        previous_ms = current_ms;
-        lag += elapsed_ms;
-        //printf("%" PRIu64 ", %" PRIu64 ", %f\n", elapsed_ms, lag, PLATFORM_MS_PER_UPDATE);
+        uint64_t current_wall_clock_time = glfwGetTimerValue();
+
+        {
+            uint64_t previous_frame_duration = current_wall_clock_time - previous_wall_clock_time;
+            previous_wall_clock_time = current_wall_clock_time;
+            dt = (float)previous_frame_duration / (float)timer_frequency;
+            // TODO: Debug periodic dropped frame on linux when fullscreen
+            printf("ms per frame: %f\n", dt * 1000.0f);
+        }
 
         int32_t framebuffer_width = PLATFORM_SCR_WIDTH;
         int32_t framebuffer_height = PLATFORM_SCR_HEIGHT;
@@ -104,11 +111,14 @@ int main(void)
                 // TODO: fall back to backup?
             }
         }
-        game_code.game_update_and_render(&game_state, lag/PLATFORM_SECOND, glmth_v2u_init(framebuffer_width, framebuffer_height));
+        // TODO: Don't make a v2u out of two i32s
+        game_code.game_update_and_render(&game_state, dt, (v2u) {framebuffer_width, framebuffer_height});
 #else
-        game_update_and_render(&game_state, lag/PLATFORM_SECOND, glmth_v2u_init(framebuffer_width, framebuffer_height));
+        // TODO: Don't make a v2u out of two i32s
+        game_update_and_render(&game_state, dt, (v2u) {framebuffer_width, framebuffer_height});
 #endif // PLATFORM_HOTLOAD_GAME_CODE
 
+        // TODO: Do something sane when vsync is disabled
         glfwSwapBuffers(window);
         glfwPollEvents();
     }
diff --git a/src/platform_linux.h b/src/platform_linux.h
@@ -1,12 +1,6 @@
 #define PLATFORM_SCR_WIDTH 600u
 #define PLATFORM_SCR_HEIGHT 600u
 
-#define PLATFORM_SECOND 1000.0f
-#define PLATFORM_FPS 60
-#define PLATFORM_MS_PER_FRAME (PLATFORM_SECOND / PLATFORM_FPS)
-#define PLATFORM_UPDATES_PER_SECOND 120
-#define PLATFORM_MS_PER_UPDATE (PLATFORM_SECOND / PLATFORM_UPDATES_PER_SECOND)
-
 #ifdef PLATFORM_HOTLOAD_GAME_CODE
 #define PLATFORM_GAME_LIB_PATH "./out/release/game.so"
 struct GameCode