now supporting sim-time

src/main.rs

@@ -1,72 +1,18 @@
 use core::time;
-use std::{ops::Bound, time::{Duration, Instant}};
+use std::time::{Duration, Instant};
-use rand::Rng;
 
-// loop constants
+// sim constants
+// update interval is the minimum delay (in milliseconds) between update ticks
 const UPDATE_INTERVAL: u32 = 40;
+// timescale is the rate of the simulation proportional to real-time
+const TIMESCALE: f32 = 1.0;
 
 // debug constants
 const DEBUG_LOOP: bool = false;
-const DEBUG_TIME: bool = false;
+const DEBUG_TIME: bool = true;
-const DEBUG_PARTICLES: bool = true;
-
-// scene constants
-const TIMESCALE: f32 = 1.0;
-const SIM_BOUNDS: BoundingBox = BoundingBox {
-    size: [10.0, 10.0, 10.0],
-    offset: [-5.0, -5.0, 0.0]
-};
-const GRAVITY: f32 = -9.8;
-const PARTICLE_COUNT: i32 = 1;
-
-// a struct made for defining a bounding box
-#[derive(Copy, Clone)]
-struct BoundingBox {
-    size: [f32; 3],
-    offset: [f32; 3]
-}
-
-impl BoundingBox {
-    // return the lower bounds
-    fn lower(&self) -> [f32; 3] {
-        self.offset
-    }
-
-    // return the upper bounds
-    fn upper(&self) -> [f32; 3] {
-        let mut bounds: [f32; 3] = [0.0; 3];
-
-        for i in 0..3 {
-            bounds[i] = self.size[i] + self.offset[i];
-        }
-
-        bounds
-    }
-}
-
-#[derive(Copy, Clone)]
-struct PlaneCollider {
-    location: [f32; 3],
-    normal: [f32; 3]
-}
-
-impl PlaneCollider {
-    // returns if a location is outside the plane's space (past the plane in the direction of the plane's normal)
-    fn is_outside(&self, point: [f32; 3]) -> bool {
-        true
-    }
-}
-
-// a struct made for physics particles
-#[derive(Copy, Clone)]
-struct Particle {
-	location: [f32; 3],
-	velocity: [f32; 3],
-    acceleration: [f32; 3],
-    gravity_enabled: bool
-}
 
 fn main() {
+    // allow the simulation to be stopped from within the loop (by setting simulate to false)
     let mut simulate: bool = true;
     
     // start the clock to keep track of real time
@@ -75,121 +21,57 @@ fn main() {
     // keep track of the last tick time
     let mut last_tick = Instant::now();
 
-    // a vector of particles
+    // real-time and sim-time clocks
-    let mut particles: Vec<Particle> = vec![];
+    let mut real_time = Duration::new(0, 0);
-    for i in 0..PARTICLE_COUNT {
+    let mut sim_time = Duration::new(0, 0);
-        // each particle spawned at a random location within the sim bounds
-        let new_particle = Particle {
-            location: [0.0, 0.0, 5.0],
-            velocity: [0.0; 3],
-            acceleration: random_vector3([100.0; 3], [-50.0; 3]),
-            gravity_enabled: false
-        };
-
-        particles.push(new_particle)
-    }
 
     while simulate {
-        // update
+        // TODO - support frameskips
         if delta_time(last_tick) >= UPDATE_INTERVAL {
+            // update clocks
+            let elapsed_time = Instant::now().duration_since(last_tick);
+            real_time += elapsed_time;
+            sim_time += elapsed_time.mul_f32(TIMESCALE);
+
             // DEBUG
             if DEBUG_TIME {
-                println!("Real time: {}ms | Delta time: {}ms", delta_time(clock_start), delta_time(last_tick));
+                println!("Real time: {}ms | Sim time: {}ms | Delta time: {}ms", real_time.as_millis(), sim_time.as_millis(), delta_time(last_tick));
-            }
-            if DEBUG_PARTICLES {
-                for i in 0..particles.len() {
-                    println!("Time: {}ms | Delta time: {} | Particle {} Location: {:?}, Velocity: {:?}, Acceleration: {:?}", delta_time(clock_start), delta_time(last_tick), i, particles[i].location, particles[i].velocity, particles[i].acceleration);
-                }
             }
 
-            update(delta_time(last_tick), &mut particles);
+            // update
+            update(delta_time(last_tick), TIMESCALE);
 
             // record last tick time
             last_tick = Instant::now();
         }
 
-        //display(delta_time, &test_particle);
+        // display
+        display(delta_time(last_tick), TIMESCALE);
     }
 }
 
 // update function
-// TODO - I think I'm resetting delta time in the wrong place or just using it incorrectly; frameskips aren't happening at all
+// this is where all your per-tick logic should go
-fn update(delta_time: u32, particles: &mut Vec<Particle>) {
+fn update(delta_time: u32, timescale: f32) {
-    if DEBUG_LOOP {
-        println!("Updating");
-    }
-
-    // calculate the exact timestep (fractional time in seconds) from delta time
-    let timestep: f32 = delta_time as f32 / 1000.0;
-    
-    for particle in particles.iter_mut() {
-        // add gravitational constant to instantaneous acceleration
-        if particle.gravity_enabled {
-            // acceleration += constant
-            particle.acceleration[2] += GRAVITY;
-        }
-        
-        // update velocity
-        for i in 0..3 {
-            // velocity += timestep * acceleration
-            particle.velocity[i] = timestep.mul_add(particle.acceleration[i], particle.velocity[i]);
-
-            // kill instantaneous acceleration
-            particle.acceleration[i] = 0.0;
-        }
-        
-        // update location
-        for i in 0..3 {
-            // location += timestep * velocity
-            particle.location[i] = timestep.mul_add(particle.velocity[i], particle.location[i]);
-        }
-    
-        // prevent the particle from exiting the sim bounds by clamping its position and killing its velocity upon "hitting" a wall
-        let upper_bounds = SIM_BOUNDS.upper();
-        let lower_bounds = SIM_BOUNDS.lower();
-        for i in 0..3 {
-            if particle.location[i] >= upper_bounds[i] {
-                particle.location[i] = upper_bounds[i];
-                particle.velocity[i] = 0.0;
-            } else if particle.location[i] <= lower_bounds[i] {
-                particle.location[i] = lower_bounds[i];
-                particle.velocity[i] = 0.0;
-            }
-        }
-    }
-}
-
-// render function
-fn display(delta_time: u32, particle: &Particle) {
-    // calculate interpolation via delta time
-    let interpolation: f32 = delta_time as f32 / UPDATE_INTERVAL as f32;
-
     // DEBUG
     if DEBUG_LOOP {
-        println!("Displaying | Delta Time: {}ms | Relative Time: {}", delta_time, interpolation);
+        println!("Updating...");
     }
 
+    // use timestep to scale per-tick calculations appropriately
+    let timestep: f32 = delta_time as f32 / 1000.0 * timescale;
+}
+
+// display function
+// this is where you should call a render function
+fn display(delta_time: u32, timescale: f32) {
     // DEBUG
-    // println!("test_particle | Location: {:?} | Velocity: {:?}", render_particle.location, render_particle.velocity);
+    if DEBUG_LOOP {
+        println!("Displaying...");
     }
 
-// 1D linear interpolation
+    // use interpolation to smooth display values between ticks
-fn lerp_1d(x: f64, y: f64, a: f64) -> f64 {
+    let interpolation: f32 = delta_time as f32 / UPDATE_INTERVAL as f32 * timescale;
-    x + ((y - x) * a)
-}
-
-// returns a vector3 with random components
-fn random_vector3(scale: [f32; 3], offset: [f32; 3]) -> [f32; 3] {
-    let mut rng = rand::thread_rng();
-
-    let mut vector3: [f32; 3] = [0.0; 3];
-
-    for i in 0..3 {
-        let component = rng.gen::<f32>();
-        vector3[i] = component.mul_add(scale[i], offset[i]);
-    }
-
-    vector3
 }
 
 // gets the time in milliseconds that's elapsed since the earlier Instant