From 6e78329eb56b8e608f6b8a082a4cbda08bfdca13 Mon Sep 17 00:00:00 2001
From: Aadhavan Srinivasan <aadhavan@twomorecents.org>
Date: Thu, 18 Jan 2024 19:30:11 -0500
Subject: [PATCH] Updated code to use variable paddle speed and keep a constant
 speed (magnitude of velocity); added function to determine the x and y
 components of ball velocity after collision with paddle

---
 main.cpp | 56 ++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 42 insertions(+), 14 deletions(-)

diff --git a/main.cpp b/main.cpp
index efe934b..766e7ec 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1,16 +1,43 @@
 #include <iostream>
+#include <cmath>
 #include <raylib-cpp.hpp>
 #include "paddle.hpp"
 #include "ball.hpp"
+#include "math-helpers.hpp"
 
-int main() {
-	/* Initialize variables used to instantiate structs*/
-	const int WIDTH = 600;
-	const int HEIGHT = 480;
-	const int RECT_H = HEIGHT / 3;
-	const int RECT_W = 30;
-	const int CIRC_RAD = 10;
+/* Global variables used to instantiate structs */
+const int WIDTH = 1000;
+const int HEIGHT = 480;
+const int RECT_H = HEIGHT / 3;
+const int RECT_W = 30;
+const int PADDLE_SPEED = 8;
+const int CIRC_RAD = 10;
+const float BASE_BOUNCE_DEG = 30;
+const float BASE_BOUNCE_RAD = (BASE_BOUNCE_DEG / 180.0) * M_PI;
+const float BASE_SPEED_COMPONENTS = 7;
+const float BASE_SPEED = sqrt(powf(BASE_SPEED_COMPONENTS, 2) * 2);
+
+raylib::Vector2 changeVelocityAfterCollision(Paddle paddle, Ball ball) {
+	float paddle_mid_y = (paddle.getRect().y + paddle.getRect().GetHeight()) / 2.0; /* Middle y value of rectangle */
+	float  ball_y = ball.pos.y; /* Y co-ordinate of ball */
+
+	float offset = paddle_mid_y - ball_y; /* Subtracting the ball coordinate will give us a value between -paddle_mid_y (represents bottom of paddle) and +paddle_mid_y (represents top of paddle) */
+	offset /= (paddle.getRect().GetHeight() / 2.0); /* Normalize the value, by dividing it by its magnitude. It is now a value between -1 and 1. */
+//	offset *= -1; /* Reverse the sign of the offset, so that -1 represents the top, and 1 represents the bottom */
+
+	float bounce_angle = offset * BASE_BOUNCE_RAD; /* Calculate the actual bounce angle from the base bounce angle. */
+
+	/* Calculate new velocities as multiples of the original velocity. I use sine and cosine, because when the ball hits the paddle
+	perpendicular to it (bounce angle is 0), the y_velocity should be 0 (i.e. It should bounce straight back). The sin function does
+	this for us. A similar reasoning was employed for the use of cosine */
+	float new_x_vel = abs(BASE_SPEED * cosf(bounce_angle)) * (-1 * signum(ball.vel.x)); /* Reverse the sign of the x-velocity */
+	float new_y_vel = abs(BASE_SPEED * sinf(bounce_angle)) * signum(ball.vel.y); /* Keep the sign of the y-velocity */
 
+	return raylib::Vector2(new_x_vel, new_y_vel);
+}
+
+
+int main() {
 	/* Initialize window */
 	raylib::Window window = raylib::Window(WIDTH, HEIGHT, "Pong");
 	SetTraceLogLevel(LOG_INFO);
@@ -21,7 +48,7 @@ int main() {
 	/* Instantiate Paddle and Ball objects */
 	Paddle pad1 = Paddle(10, 10, RECT_W, RECT_H);
 	Paddle pad2 = Paddle(window.GetWidth() - RECT_W - 10, 10, RECT_W, RECT_H);
-	Ball ball = Ball(window.GetWidth()/2, window.GetHeight()/2, CIRC_RAD, 3, 3);
+	Ball ball = Ball(window.GetWidth()/2, window.GetHeight()/2, CIRC_RAD, 5, 5);
 
 	window.BeginDrawing();
 	pad1.draw();
@@ -32,10 +59,10 @@ int main() {
 	while (!window.ShouldClose()) {
 		/* Update paddle velocity */
 		if (IsKeyPressed(KEY_S)) {
-			pad1.velocity.y = 5; /* Set positive (downward) velocity, since (0,0) is top-left */
+			pad1.velocity.y = PADDLE_SPEED; /* Set positive (downward) velocity, since (0,0) is top-left */
 		}
 		if (IsKeyPressed(KEY_W)) {
-			pad1.velocity.y = -5; /* Set negative (upward) velocity */
+			pad1.velocity.y = (-1) * PADDLE_SPEED; /* Set negative (upward) velocity */
 		}
 
 		if (IsKeyReleased(KEY_S) || IsKeyReleased(KEY_W)) {
@@ -43,10 +70,10 @@ int main() {
 		}
 
 		if (IsKeyPressed(KEY_UP)) {
-			pad2.velocity.y = -5;
+			pad2.velocity.y = (-1) * PADDLE_SPEED;
 		}
 		if (IsKeyPressed(KEY_DOWN)) {
-			pad2.velocity.y = 5;
+			pad2.velocity.y = PADDLE_SPEED;
 		}
 		if (IsKeyReleased(KEY_UP) || IsKeyReleased(KEY_DOWN)) {
 			pad2.velocity.y = 0;
@@ -54,12 +81,13 @@ int main() {
 
 		/* Update ball velocity based on collision detection */
 		if (pad1.getRect().CheckCollision(ball.pos, ball.radius)) { /* Collision with paddle 1 */
-			ball.vel.x = ball.vel.x * (-1);
 			ball.pos.x = pad1.getRect().x + pad1.getRect().GetWidth() + ball.radius + 1; /* Ensuring that the ball doesn't get stuck inside the paddle */
+			ball.vel = changeVelocityAfterCollision(pad1, ball);
+
 		}
 		if (pad2.getRect().CheckCollision(ball.pos, ball.radius)) { /* Collision with paddle 2 */
-			ball.vel.x = ball.vel.x * (-1);
 			ball.pos.x = pad2.getRect().x - ball.radius - 1;
+			ball.vel = changeVelocityAfterCollision(pad2, ball);
 		}
 
 		if (ball.pos.x + ball.radius >= window.GetWidth()) { /* Collision with right wall */