breakout: add collision between paddle and ball

2 files changed, 25 insertions, 4 deletions

diff --git a/src/games/breakout/Breakout.cpp b/src/games/breakout/Breakout.cpp
index 62ee17c..38d356c 100644
--- a/src/games/breakout/Breakout.cpp
+++ b/src/games/breakout/Breakout.cpp
@@ -3,6 +3,7 @@
 #include "games/Game.hpp"
 #include "common/shapes.hpp"
 #include "renderer/Renderer.hpp"
+#include <cmath>
 
 
 void
@@ -17,7 +18,7 @@ Breakout::Start()
     m_ball.circle.y = 2.0f;
     m_ball.circle.r = 0.05f;
     m_ball.dx = 0.0f;
-    m_ball.dy = 1.0f;
+    m_ball.dy = BALL_SPEED;
 
 
     float brickmap_w = 1.00f * MAP_WIDTH;
@@ -126,14 +127,32 @@ Breakout::MoveBall(float dt)
     }
 
     // collision paddle
+    // Todo: Handle collisions on the side of the paddle near the bottom.
+    //       Those should end up in game over somehow.
     Rectangle paddle_rect = {
         m_paddle.x,
         0.0f,
         m_paddle.x + PADDLE_WIDTH,
         PADDLE_HEIGHT
     };
-    if (Intersect_Rectangle_Circle(paddle_rect, m_ball.circle)) {
-        m_ball.dy = std::abs(m_ball.dy);
+    if (Intersect_AABB_Circle(paddle_rect, m_ball.circle)) {
+        // Todo: find a better name than 'percent' (which represents [0.0, 1.0] here instead of the expected [0, 100]).
+        float rect_half_width = (paddle_rect.x1 - paddle_rect.x0) / 2;
+        float rect_center_x = paddle_rect.x0 + rect_half_width;
+        float dist_x = m_ball.circle.x - rect_center_x;
+        float dist_x_percent = dist_x / rect_half_width;
+
+        float max_dx_percent = 0.7f;
+        float dx_percent = dist_x_percent * max_dx_percent;
+        float dy_percent = 1.0f - dx_percent;
+
+        float length = std::sqrt(dx_percent*dx_percent + dy_percent*dy_percent);
+        float dx = BALL_SPEED * (dx_percent / length);
+        float dy = BALL_SPEED * (dy_percent / length);
+
+        m_ball.circle.y += paddle_rect.y1 -(m_ball.circle.y - m_ball.circle.r);
+        m_ball.dx = dx;
+        m_ball.dy = dy;
     }
 }
 
diff --git a/src/games/breakout/Breakout.hpp b/src/games/breakout/Breakout.hpp
index 2b7c9b3..60cd648 100644
--- a/src/games/breakout/Breakout.hpp
+++ b/src/games/breakout/Breakout.hpp
@@ -22,8 +22,10 @@ class Breakout : public Game {
     static constexpr uint32_t BRICK_ROWS = 8;
     static constexpr uint32_t BRICK_COLS = 14;
 
-    static constexpr float PADDLE_HEIGHT = 0.1f;
+    static constexpr float BALL_SPEED = 2.0f;
+
     static constexpr float PADDLE_WIDTH = 0.6f;
+    static constexpr float PADDLE_HEIGHT = 0.1f;
     static constexpr float PADDLE_SPEED = 1.0f;