From 08a97e2f39961a79dd57e7310626408b20c5d9e8 Mon Sep 17 00:00:00 2001
From: taw27 <taw27@84d2e878-0bd5-11dd-ad15-13eda11d74c5>
Date: Thu, 7 Aug 2008 23:13:07 +0000
Subject: Measure and subtract physics time from the wait

git-svn-id: svn://cook.msm.cam.ac.uk:745/thrust3d/thrust3d@233 84d2e878-0bd5-11dd-ad15-13eda11d74c5
---
 src/game.c    |  3 ++-
 src/main.c    |  6 ++++--
 src/physics.c | 13 +++++++++++++
 src/render.c  |  4 +++-
 src/types.h   |  3 ++-
 5 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/src/game.c b/src/game.c
index a5727be..9ef3019 100644
--- a/src/game.c
+++ b/src/game.c
@@ -292,7 +292,8 @@ Game *game_new(int width, int height, GameOptions gameopts) {
 	g->t_fps = SDL_GetTicks();
 	g->fps = 0;
 	g->query_this_frame = 1;
-	g->time_to_render = 0;
+	g->time_render = 30000;
+	g->time_physics = 0;
 	g->fuel = 1.0;
 	g->radiation = 0.1;
 	g->platform_rel_x = 0.0;
diff --git a/src/main.c b/src/main.c
index 49c0bd9..9456b56 100644
--- a/src/main.c
+++ b/src/main.c
@@ -292,8 +292,10 @@ int main(int argc, char *argv[]) {
 			game->frames = 0;
 		}
 		
-		/* Wait for how long it takes to render the frame at the most recent measurement. */
-		if ( !gameopts.no_framerate_limit ) usleep(game->time_to_render/1000);
+		/* Wait for how long it takes the graphics card to catch up, at the most recent measurement. */
+		if ( game->time_physics < game->time_render ) {
+			if ( !gameopts.no_framerate_limit ) usleep(game->time_render-game->time_physics);
+		}
 		
 	}
 	
diff --git a/src/physics.c b/src/physics.c
index 3472cc5..91505b9 100644
--- a/src/physics.c
+++ b/src/physics.c
@@ -15,6 +15,8 @@
 
 #include <SDL.h>
 #include <math.h>
+#include <sys/time.h>
+#include <time.h>
 
 #include "types.h"
 #include "model.h"
@@ -403,9 +405,14 @@ static void physics_process(ModelInstance *obj, Uint32 dt, Game *game) {
 void physics_step(Game *game, Uint32 t) {
 
 	Uint32 dt;
+	struct timeval tv;
+	suseconds_t us;
 	
 	dt = t - game->tlast;
 	
+	gettimeofday(&tv, NULL);
+	us = tv.tv_usec;
+	
 	/* Handle things specific to the lander craft */
 	if ( game->thrusting ) {
 		if ( game->fuel > 0.0 ) {
@@ -454,6 +461,12 @@ void physics_step(Game *game, Uint32 t) {
 	game_check_handoff(game);
 	
 	game->tlast = t;
+	
+	gettimeofday(&tv, NULL);
+	us = tv.tv_usec - us;
+	
+	game->time_physics = us;
+	
 
 }
 
diff --git a/src/render.c b/src/render.c
index 4b95635..5f3445c 100644
--- a/src/render.c
+++ b/src/render.c
@@ -687,7 +687,9 @@ void render_draw(Game *game, Uint32 t) {
 		GLint available;
 		glGetQueryObjectiv(game->timer_query, GL_QUERY_RESULT_AVAILABLE, &available);
 		if ( available ) {
-			glGetQueryObjectui64vEXT(game->timer_query, GL_QUERY_RESULT, &game->time_to_render);
+			GLuint64EXT time_to_render;
+			glGetQueryObjectui64vEXT(game->timer_query, GL_QUERY_RESULT, &time_to_render);
+			game->time_render = time_to_render / 1000;	/* Convert ns to us */
 			game->query_this_frame = 1;
 			glDeleteQueries(1, &game->timer_query);
 		}
diff --git a/src/types.h b/src/types.h
index 37ccf1f..d45f474 100644
--- a/src/types.h
+++ b/src/types.h
@@ -265,7 +265,8 @@ typedef struct {
 	int		fps;
 	int		query_this_frame;
 	GLuint		timer_query;
-	GLuint64EXT	time_to_render;
+	long long int	time_render;	/* Time taken to render, in us */
+	long long int	time_physics;	/* Time taken for physics, in us */
 	
 	GLfloat		radiation;
 	GLfloat		fuel;
-- 
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