From 0d578ef5b2b0befb3788b8f8405d1713b3e7ee13 Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Wed, 13 Nov 2024 10:49:41 -0500
Subject: refactor animate()

---
 balls.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/balls.c b/balls.c
index 6c8e854..567e9d8 100644
--- a/balls.c
+++ b/balls.c
@@ -80,6 +80,7 @@ void keyboard(unsigned char key, int x, int y);
 void move(void);
 void collideBalls(void);
 cl_event collideWalls(void);
+void copyPositionsToGpu(cl_event cpuEvent);
 void genVertices(void);
 void freeCL(void);
 void freeGL(void);
@@ -534,27 +535,23 @@ setKernelArgs(void) {
 void
 animate(int v) {
 	cl_event cpuEvent;
-	int err;
 	clock_t tstart, elapsed;
 	unsigned int nextFrame;
 
 	tstart = clock();
 
+	/* Start computing next frame on CPU. */
 	move();
 	collideBalls();
 	cpuEvent = collideWalls();
 
+	/* Disply current from with GPU. */
 	display();
 
-	/* Copy new positions to GPU. */
-	err = clWaitForEvents(1, &cpuEvent);
-	if (err < 0)
-		sysfatal("Error waiting for CPU kernel to finish.\n");
-	clReleaseEvent(cpuEvent);
-	err = clEnqueueWriteBuffer(gpuQueue, positionsGpuBuf, CL_TRUE, 0, nBalls*2*sizeof(float), positionsHostBuf, 0, NULL, NULL);
-	if (err < 0)
-		sysfatal("Failed to copy positions from host to GPU.\n");
+	/* Copy next frame's positions from CPU to GPU. */
+	copyPositionsToGpu(cpuEvent);
 
+	/* Display next frame. */
 	elapsed = (clock() - tstart) / (CLOCKS_PER_SEC / MS_PER_S);
 	nextFrame = (elapsed > FRAME_TIME_MS) ? 0 : FRAME_TIME_MS-elapsed;
 	glutTimerFunc(nextFrame, animate, 0);
@@ -627,6 +624,20 @@ collideWalls(void) {
 	return event;
 }
 
+/* Wait for the CPU to finish computing the new positions and then copy them to the GPU. */
+void
+copyPositionsToGpu(cl_event cpuEvent) {
+	int err;
+
+	err = clWaitForEvents(1, &cpuEvent);
+	if (err < 0)
+		sysfatal("Error waiting for CPU kernel to finish.\n");
+	clReleaseEvent(cpuEvent);
+	err = clEnqueueWriteBuffer(gpuQueue, positionsGpuBuf, CL_TRUE, 0, nBalls*2*sizeof(float), positionsHostBuf, 0, NULL, NULL);
+	if (err < 0)
+		sysfatal("Failed to copy positions from host to GPU.\n");
+}
+
 void
 genVertices(void) {
 	int err;
-- 
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