a-game

commit 45ccc3fb2925663632edc8b671ffdd4cf5f2f211
parent 2bc29b7706016ef52fc0e95369c728780d8e6661
Author: amin <dev@aminmesbah.com>
Date:   Sat, 23 Nov 2019 17:43:48 +0000

Specify jump in terms of maximum height

It's gradually becoming pleasant to move around in this world. A little
high school physics goes a long way!

FossilOrigin-Name: 75ee64faa932d8fff75c11926138b0f1d62a71afc179dd20f47fe9259b4cdb58
Diffstat:
M
src/game.c
 | 
51
++++++++++++++++++++++++++++++++++++++-------------

1 file changed, 38 insertions(+), 13 deletions(-)
diff --git a/src/game.c b/src/game.c
@@ -254,13 +254,12 @@ void game_update_and_render(struct GameMemory *game_memory, struct GameInput *ga
             dt = 1.0f / 60.0f;
         }
 
-        f32 max_velocity[] = {
-            [DIR_RIGHT] = 6.0f,
-            [DIR_LEFT] = -6.0f,
-            [DIR_UP] = 7.0f,
-            [DIR_DOWN] = -9.0f,
-        };
+        f32 max_run_speed = 6.0f;
+        f32 max_climb_speed = 7.0f;
+        f32 max_fall_speed = 9.0f;
+
         f32 acceleration_rate = 50.0f;
+        f32 gravity = 30.0f;
         f32 friction = 0.7f;
         enum Direction previous_facing_dir = player->facing;
 
@@ -385,12 +384,11 @@ void game_update_and_render(struct GameMemory *game_memory, struct GameInput *ga
 
         move_mode_print(player->move_mode);
 
-        // TODO: tune these acceleration rates
         // simulate movement mode
         switch(player->move_mode)
         {
             case MOVE_MODE_FALLING:
-                player->acceleration.y = -acceleration_rate;
+                player->acceleration.y = -gravity;
                 break;
             case MOVE_MODE_GROUNDED:
                 player->acceleration.y = 0.0f;
@@ -421,11 +419,17 @@ void game_update_and_render(struct GameMemory *game_memory, struct GameInput *ga
                 }
                 break;
             case MOVE_MODE_JUMPING:
-                // TODO: Specify jumping in terms of jump height
-                max_velocity[DIR_UP] = 1000.0f;
-                player->acceleration.y = 30.0f * acceleration_rate;
+            {
+                f32 jump_height = 2.0f;
+                // v^2  = v0^2 - 2g(y - y0)
+                // 0    = v0^2 - 2g(h - 0)
+                // 0    = v0^2 - 2gh
+                // v0^2 = 2gh
+                // v0   = sqrt(2gh)
+                player->velocity.y = sqrtf(2.0f * gravity * jump_height);
                 player->move_mode = MOVE_MODE_FALLING;
                 break;
+            }
             case MOVE_MODE_FLOATING:
                 if (btn_is_down(button_states, BTN_UP))
                 {
@@ -449,8 +453,29 @@ void game_update_and_render(struct GameMemory *game_memory, struct GameInput *ga
         // Semi implicit Euler integration: https://gafferongames.com/post/integration_basics/
         player->velocity = math_v2_a(player->velocity, math_v2f_m(player->acceleration, dt));
         // TODO: clamp the length of the velocity vector, not each of its components
-        math_clamp(&player->velocity.x, max_velocity[DIR_LEFT], max_velocity[DIR_RIGHT]);
-        math_clamp(&player->velocity.y, max_velocity[DIR_DOWN], max_velocity[DIR_UP]);
+        math_clamp(&player->velocity.x, -max_run_speed, max_run_speed);
+        switch(player->move_mode)
+        {
+            case MOVE_MODE_CLIMBING:
+                math_clamp(&player->velocity.y, -max_fall_speed, max_climb_speed);
+                break;
+            case MOVE_MODE_FALLING:
+                if (player->velocity.y < -max_fall_speed)
+                {
+                    player->velocity.y = -max_fall_speed;
+                }
+                break;
+            case MOVE_MODE_FLOATING:
+                math_clamp(&player->velocity.y, -max_run_speed, max_run_speed);
+                break;
+            default:
+                break;
+        }
+
+        printf("v: ");
+        math_print(player->velocity);
+        printf("a: ");
+        math_print(player->acceleration);
 
         // game_detect_collisions
         {