Snow ADSR (bug 221)

[supertux.git] / src / object / snow_particle_system.cpp

diff --git a/src/object/snow_particle_system.cpp b/src/object/snow_particle_system.cpp
index 406ca08..a0efa35 100644 (file)
--- a/src/object/snow_particle_system.cpp
+++ b/src/object/snow_particle_system.cpp
@@ -19,17 +19,34 @@
 #include <math.h>
 
 #include "math/random_generator.hpp"
-#include "supertux/main.hpp"
+#include "supertux/globals.hpp"
 #include "video/drawing_context.hpp"
 
-SnowParticleSystem::SnowParticleSystem()
+// TODO: tweak values
+namespace SNOW {
+static const float SPIN_SPEED = 60.0f;
+static const float WIND_SPEED = 30.0f; // max speed of wind will be randf(WIND_SPEED) * randf(STATE_LENGTH)
+static const float STATE_LENGTH = 5.0f;
+static const float DECAY_RATIO = 0.2f; // ratio of attack speed to decay speed
+static const float EPSILON = 0.5f; //velocity changes by up to this much each tick
+static const float WOBBLE_DECAY = 0.99f; //wobble decays exponentially by this much each tick
+static const float WOBBLE_FACTOR = 4 * .005f; //wobble approaches drift_speed by this much each tick
+}
+
+SnowParticleSystem::SnowParticleSystem() :
+  state(RELEASING),
+  timer(),
+  gust_onset(0),
+  gust_current_velocity(0)
 {
-  snowimages[0] = new Surface("images/objects/particles/snow2.png");
-  snowimages[1] = new Surface("images/objects/particles/snow1.png");
-  snowimages[2] = new Surface("images/objects/particles/snow0.png");
+  snowimages[0] = Surface::create("images/objects/particles/snow2.png");
+  snowimages[1] = Surface::create("images/objects/particles/snow1.png");
+  snowimages[2] = Surface::create("images/objects/particles/snow0.png");
 
   virtual_width = SCREEN_WIDTH * 2;
 
+  timer.start(.01);
+
   // create some random snowflakes
   size_t snowflakecount = size_t(virtual_width/10.0);
   for(size_t i=0; i<snowflakecount; ++i) {
@@ -39,13 +56,18 @@ SnowParticleSystem::SnowParticleSystem()
     particle->pos.x = systemRandom.randf(virtual_width);
     particle->pos.y = systemRandom.randf(SCREEN_HEIGHT);
     particle->anchorx = particle->pos.x + (systemRandom.randf(-0.5, 0.5) * 16);
+    // drift will change with wind gusts
     particle->drift_speed = systemRandom.randf(-0.5, 0.5) * 0.3;
     particle->wobble = 0.0;
 
     particle->texture = snowimages[snowsize];
+    particle->flake_size = powf(snowsize+3,4); // since it ranges from 0 to 2
 
-    particle->speed = 1 + (2 - snowsize)/2 + systemRandom.randf(1.8);
-    particle->speed *= 20; // gravity
+    particle->speed = 2 * (1 + (2 - snowsize)/2 + systemRandom.randf(1.8)) * 10; // gravity
+
+    // Spinning
+    particle->angle = systemRandom.randf(360.0);
+    particle->spin_speed = systemRandom.randf(-SNOW::SPIN_SPEED,SNOW::SPIN_SPEED);
 
     particles.push_back(particle);
   }
@@ -59,25 +81,64 @@ SnowParticleSystem::parse(const Reader& reader)
 
 SnowParticleSystem::~SnowParticleSystem()
 {
-  for(int i=0;i<3;++i)
-    delete snowimages[i];
 }
 
 void SnowParticleSystem::update(float elapsed_time)
 {
+  // Simple ADSR wind gusts
+
+  if (timer.check()) {
+    // Change state
+    state = (State) ((state + 1) % MAX_STATE);
+
+    if(state == RESTING) {
+      // stop wind
+      gust_current_velocity = 0;
+      // new wind strength
+      gust_onset   = systemRandom.randf(-SNOW::WIND_SPEED, SNOW::WIND_SPEED);
+    }
+    timer.start(systemRandom.randf(SNOW::STATE_LENGTH));
+  }
+
+  // Update velocities
+  switch(state) {
+    case ATTACKING:
+      gust_current_velocity += gust_onset * elapsed_time;
+      break;
+    case DECAYING:
+      gust_current_velocity -= gust_onset * elapsed_time * SNOW::DECAY_RATIO;
+      break;
+    case RELEASING:
+      // uses current time/velocity instead of constants
+      gust_current_velocity -= gust_current_velocity * elapsed_time / timer.get_timeleft();
+      break;
+    case SUSTAINING:
+    case RESTING:
+      //do nothing
+      break;
+    default:
+      assert(false);
+  }
+
   std::vector<Particle*>::iterator i;
 
   for(i = particles.begin(); i != particles.end(); ++i) {
     SnowParticle* particle = (SnowParticle*) *i;
     float anchor_delta;
 
+    // Falling
     particle->pos.y += particle->speed * elapsed_time;
-    particle->pos.x += particle->wobble * elapsed_time /* * particle->speed * 0.125*/;
-
-    anchor_delta = (particle->anchorx - particle->pos.x);
-    particle->wobble += (4 * anchor_delta * 0.05) + systemRandom.randf(-0.5, 0.5);
-    particle->wobble *= 0.99f;
+    // Drifting (speed approaches wind at a rate dependent on flake size)
+    particle->drift_speed += (gust_current_velocity - particle->drift_speed) / particle->flake_size + systemRandom.randf(-SNOW::EPSILON,SNOW::EPSILON);
     particle->anchorx += particle->drift_speed * elapsed_time;
+    // Wobbling (particle approaches anchorx)
+    particle->pos.x += particle->wobble * elapsed_time;
+    anchor_delta = (particle->anchorx - particle->pos.x);
+    particle->wobble += (SNOW::WOBBLE_FACTOR * anchor_delta) + systemRandom.randf(-SNOW::EPSILON, SNOW::EPSILON);
+    particle->wobble *= SNOW::WOBBLE_DECAY;
+    // Spinning
+    particle->angle += particle->spin_speed * elapsed_time;
+    particle->angle = fmodf(particle->angle, 360.0);
   }
 }