Fixed orbit

main.c

@@ -1,17 +1,16 @@
 #define _POSIX_C_SOURCE 200809L
 #include "consts.h"
 #include "gravity.h"
-#include "mechanics.h"
 #include "magnetism.h"
+#include "mechanics.h"
 #include "objects.h"
 #include "vec_utils.h"
-#include <bits/time.h>
+#include <errno.h>
 #include <math.h>
 #include <pthread.h>
 #include <raylib.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <threads.h>
 #include <time.h>
 #include <unistd.h>
 
@@ -23,33 +22,31 @@ static inline int center_y_text(int height, int size) {
   return (height - size) / 2;
 }
 
-long long timespec_diff_ns(struct timespec end, struct timespec start) {
-  return (end.tv_sec - start.tv_sec) * 1000000000LL +
-         (end.tv_nsec - start.tv_nsec);
-}
-
 void *physics(void *args) {
   universe_t *uni = (universe_t *)args;
-  struct timespec ot, ct;
+  struct timespec next_step;
+  clock_gettime(CLOCK_MONOTONIC, &next_step);
   while (true) {
-    clock_gettime(CLOCK_MONOTONIC, &ct);
-    gravity(uni);
-    mechanics(uni);
-    magnetism(uni);
-    ot = ct;
-    long long elapsed = timespec_diff_ns(ct, ot);
-    long long remaining = TIMESTEP / simx - elapsed;
-
-    if (remaining > 0) {
-      long long sleep_time = remaining * 9 / 10;
-
-      struct timespec sleep_time_spec = {0, sleep_time};
-      thrd_sleep(&sleep_time_spec, NULL);
+    next_step.tv_sec += LOOP_TIMESTEP / 1000000000LL;
+    next_step.tv_nsec += LOOP_TIMESTEP % 1000000000LL;
+    if (next_step.tv_nsec >= 1000000000L) {
+      next_step.tv_nsec -= 1000000000L;
+      next_step.tv_sec++;
+    }
+    gravity(uni);
+    magnetism(uni);
+    mechanics(uni);
+    struct timespec now;
+    clock_gettime(CLOCK_MONOTONIC, &now);
+    if (now.tv_sec > next_step.tv_sec ||
+        (now.tv_sec == next_step.tv_sec && now.tv_nsec > next_step.tv_nsec)) {
+      next_step =
+          now; // An overrun starts a fresh schedule, without catch-up steps.
+    }
+    // Sleep only until the deadline; processing time is already included.
+    while (clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &next_step, NULL) ==
+           EINTR) {
     }
-
-    do {
-      clock_gettime(CLOCK_MONOTONIC, &ct);
-    } while (timespec_diff_ns(ct, ot) < TIMESTEP / simx);
   }
 }
 
@@ -60,22 +57,27 @@ int main(void) {
   const char *welcome_text = "Welcome to Fucked Physics!";
   universe_t universe = {0, NULL};
   universe.bodies = malloc(1024 * sizeof(mass_body_t));
-  universe.num_bodies = 5;
+  universe.num_bodies = 7;
 
   universe.bodies[0] =
-      (mass_body_t){330432.0f, 696, {-0, 0}, {0, 0}, 696};
-  universe.bodies[1] =
-      (mass_body_t){0.055f, 2.439, {0.387*UA/RT, 0}, {0, -38.86/RT}, 50};
-  universe.bodies[2] =
-      (mass_body_t){0.815f, 0.1, {0.723*UA/RT, 0}, {0, -34.79/RT}, 50};
-  universe.bodies[3] =
-      (mass_body_t){1.0f, 0.1, {1*UA/RT, 0}, {0, -29.29/RT}, 50};
-  universe.bodies[4] =
-      (mass_body_t){0.107f, 200, {1.524*UA/RT, 0}, {0, -21.97/RT}, 200};
-  universe.bodies[5] =
-      (mass_body_t){317.83f, 0.1, {5.203*UA/RT, 0}, {0, -12.43/RT}, 50};
-  universe.bodies[6] =
-      (mass_body_t){95.159f, 200, {9.582*UA/RT, 0}, {0, -9.11/RT}, 200};
+      (mass_body_t){330432.0f, 696340 / RT, {0, 0}, {0, 0}, 600, 0, "Sun"};
+  universe.bodies[1] = (mass_body_t){
+      0.055f, 2439.7 / RT, {0.387 * UA / RT, 0}, {0, -38.86 / RT}, 80,
+      0,      "Mercury"};
+  universe.bodies[2] = (mass_body_t){
+      0.815f, 6051.8 / RT, {0.723 * UA / RT, 0}, {0, -34.79 / RT}, 190,
+      0,      "Venus"};
+  universe.bodies[3] = (mass_body_t){
+      1.0f, 1.0f, {1 * UA / RT, 0}, {0, -29.29 / RT}, 200, 0, "Earth"};
+  universe.bodies[4] = (mass_body_t){
+      0.107f, 3389.5 / RT, {1.524 * UA / RT, 0}, {0, -21.97 / RT}, 106,
+      0,      "Mars"};
+  universe.bodies[5] = (mass_body_t){
+      317.83f, 69911 / RT, {5.203 * UA / RT, 0}, {0, -12.43 / RT}, 400,
+      0,       "Jupiter"};
+  universe.bodies[6] = (mass_body_t){
+      95.159f, 58232 / RT, {9.582 * UA / RT, 0}, {0, -9.11 / RT}, 300,
+      0,       "Saturn"};
   SetConfigFlags(FLAG_WINDOW_RESIZABLE);
   InitWindow(800, 450, "Fucked Physics");
   SetTargetFPS(120);
@@ -116,14 +118,18 @@ int main(void) {
       }
     } while (key_pressed != 0);
 
-    if (IsMouseButtonPressed(MOUSE_LEFT_BUTTON) ||
-        IsMouseButtonDown(MOUSE_RIGHT_BUTTON)) {
+    if (universe.num_bodies < 1024 &&
+        (IsMouseButtonPressed(MOUSE_LEFT_BUTTON) ||
+         IsMouseButtonDown(MOUSE_RIGHT_BUTTON))) {
       Vector2 mouse_pos = vec2_scale(
           transform_to_center(vec2_scale(GetMousePosition(), -1)), -1);
       mouse_pos = vec2_scale(mouse_pos, 1 / v_scale);
 
       universe.bodies[universe.num_bodies] =
-          (mass_body_t){100000.0f, 0.1, mouse_pos, {0, 0}, 10};
+          (mass_body_t){100000.0f, 0.1, mouse_pos, {0, 0}, 10, 0, ""};
+      snprintf(universe.bodies[universe.num_bodies].name,
+               sizeof(universe.bodies[universe.num_bodies].name), "Body %u",
+               universe.num_bodies + 1);
       universe.num_bodies++;
     }
 
@@ -153,10 +159,15 @@ int main(void) {
       Vector2 scaled_offset = vec2_scale(canvas_offset, v_scale);
       Vector2 body_position = vec2_scale(universe.bodies[i].position, v_scale);
       body_position = vec2_sum(body_position, scaled_offset);
-      DrawCircleV(transform_to_center(body_position),
-                  universe.bodies[i].draw_radius * v_scale,
+      body_position = transform_to_center(body_position);
+      float draw_radius = universe.bodies[i].draw_radius * v_scale;
+      DrawCircleV(body_position, draw_radius,
                   (Color){((256 / universe.num_bodies) * i) % 256 / 2,
                           255 * (i % 2) / 2, 255 * (i % 2) * (i % 3) / 2, 255});
+      // Keep labels readable at every zoom level.
+      DrawText(universe.bodies[i].name,
+               (int)(body_position.x + draw_radius + 6),
+               (int)(body_position.y - 8), 16, BLACK);
     }
 
     DrawText(welcome_text, center_x_text(welcome_text, GetRenderWidth(), 20),