From 7f4e8d55232c076ec8e433e835928aeef55c354c Mon Sep 17 00:00:00 2001
From: Matt Turner <mattst88@gmail.com>
Date: Tue, 9 Feb 2010 19:13:26 -0500
Subject: Calculate Paddle velocity in (x,y) at time of collision.

Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 Makefile   |  2 +-
 glpong3d.c | 18 +++++++++++++++---
 paddle.c   | 18 ++++++++++--------
 paddle.h   | 11 +++++++++++
 4 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index fe425b8..21580a8 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 CC=gcc
 STRIP=strip
-WARN=-Wall -W -ansi -pedantic -DDEBUG
+WARN=-Wall -W -pedantic -DDEBUG
 CFLAGS=-ggdb -g3 -pipe -std=c99 ${WARN}
 LDFLAGS=-Wl,-O1,-s
 INCLUDES=`sdl-config --cflags`
diff --git a/glpong3d.c b/glpong3d.c
index 2fd98f6..c8cf85f 100644
--- a/glpong3d.c
+++ b/glpong3d.c
@@ -205,15 +205,27 @@ GLPong_Move(GLPong_t * GLPong) {
 
 	GLPong_BallMove(&GLPong->ball);
 
-	if (GLPong_Collide(&GLPong->ball, &GLPong->front_paddle)
-		|| GLPong_Collide(&GLPong->ball, &GLPong->back_paddle)) {
+	if (GLPong_Collide(&GLPong->ball, &GLPong->front_paddle)) {
 		if (GLPong->ball.zv < 0) {
 			GLPong->ball.zv -= 0.005f;
 		} else {
 			GLPong->ball.zv += 0.005f;
 		}
 #ifdef DEBUG
-		printf("Collision: x: %.3f, y: %.2f, z: %.2f\n", GLPong->ball.x, GLPong->ball.y, GLPong->ball.z);
+		printf("Collision: x: %.3f, y: %.2f, z: %.2f\n\tPaddle: xv: %.3f, yv: %.3f\n",
+			GLPong->ball.x, GLPong->ball.y, GLPong->ball.z,
+			GLPong_PaddleXV(&GLPong->front_paddle), GLPong_PaddleYV(&GLPong->front_paddle));
+#endif
+	} else if (GLPong_Collide(&GLPong->ball, &GLPong->back_paddle)) {
+		if (GLPong->ball.zv < 0) {
+			GLPong->ball.zv -= 0.005f;
+		} else {
+			GLPong->ball.zv += 0.005f;
+		}
+#ifdef DEBUG
+		printf("Collision: x: %.3f, y: %.2f, z: %.2f\n\tPaddle: xv: %.3f, yv: %.3f\n",
+			GLPong->ball.x, GLPong->ball.y, GLPong->ball.z,
+			GLPong_PaddleXV(&GLPong->back_paddle), GLPong_PaddleYV(&GLPong->back_paddle));
 #endif
 	}
 }
diff --git a/paddle.c b/paddle.c
index 4c4c9f0..78bc189 100644
--- a/paddle.c
+++ b/paddle.c
@@ -67,6 +67,8 @@ GLPong_PaddleInit(Paddle_t * paddle, GLfloat z, GLuint texture) {
 	paddle->x = paddle->w / 2.0f;
 	paddle->y = paddle->h / 2.0f;
 	paddle->z = z;
+	paddle->prev_x = paddle->x;
+	paddle->prev_y = paddle->y;
 	paddle->r = 1.0f;
 	paddle->g = 1.0f;
 	paddle->b = 1.0f;
@@ -76,10 +78,10 @@ GLPong_PaddleInit(Paddle_t * paddle, GLfloat z, GLuint texture) {
 
 void
 GLPong_PaddleMove(Paddle_t * paddle, GLfloat x, GLfloat y) {
-	GLfloat old_x = paddle->x;
-	GLfloat old_y = paddle->y;
 	GLfloat mouse_x;
 	GLfloat mouse_y;
+	paddle->prev_x = paddle->x;
+	paddle->prev_y = paddle->y;
 
 	/* clamp paddle to border */
 	if (x <= -1.5f + (paddle->w / 2.0f)) {
@@ -99,12 +101,12 @@ GLPong_PaddleMove(Paddle_t * paddle, GLfloat x, GLfloat y) {
 
 #ifdef DEBUG
 	printf("(mouse_x, mouse_y) = (%.3f, %.3f)\n", mouse_x, mouse_y);
-	printf("x diff is %f\n", fabs(mouse_x - old_x));
-	printf("y diff is %f\n", fabs(mouse_y - old_y));
+	printf("x diff is %f\n", fabs(mouse_x - paddle->prev_x));
+	printf("y diff is %f\n", fabs(mouse_y - paddle->prev_y));
 #endif
 
-	if (fabs(mouse_x - old_x) > 0.33f / 2.0f) {
-		if (mouse_x > old_x) {
+	if (fabs(mouse_x - paddle->prev_x) > 0.33f / 2.0f) {
+		if (mouse_x > paddle->prev_x) {
 			paddle->x += 0.33f / 2.0f;
 		} else {
 			paddle->x -= 0.33f / 2.0f;
@@ -113,8 +115,8 @@ GLPong_PaddleMove(Paddle_t * paddle, GLfloat x, GLfloat y) {
 		paddle->x = mouse_x;
 	}
 
-	if (fabs(mouse_y - old_y) > 0.25f / 2.0f) {
-		if (mouse_y > old_y) {
+	if (fabs(mouse_y - paddle->prev_y) > 0.25f / 2.0f) {
+		if (mouse_y > paddle->prev_y) {
 			paddle->y += 0.25f / 2.0f;
 		} else {
 			paddle->y -= 0.25f / 2.0f;
diff --git a/paddle.h b/paddle.h
index 61962e7..9570717 100644
--- a/paddle.h
+++ b/paddle.h
@@ -6,6 +6,7 @@
 
 typedef struct {
 	GLfloat x, y, z;
+	GLfloat prev_x, prev_y;
 	GLfloat w, h;
 	GLfloat r, g, b;
 } Paddle_t;
@@ -14,4 +15,14 @@ void GLPong_PaddleDraw(const Paddle_t * paddle);
 void GLPong_PaddleInit(Paddle_t * paddle, GLfloat z, GLuint texture);
 void GLPong_PaddleMove(Paddle_t * paddle, GLfloat x, GLfloat y);
 
+static inline GLfloat
+GLPong_PaddleXV(const Paddle_t * paddle) {
+	return paddle->x - paddle->prev_x;
+}
+
+static inline GLfloat
+GLPong_PaddleYV(const Paddle_t * paddle) {
+	return paddle->y - paddle->prev_y;
+}
+
 #endif /* PADDLE_H */
-- 
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