Removed calls to resizeBox for nitro emitter

data/shaders/pointemitter.vert

@@ -39,19 +39,23 @@ void main(void)
         if (gl_VertexID < level)
         {
             float dt_from_last_frame = fract(updated_lifetime) * lifetime_initial;
-            float coeff = 1. - dt_from_last_frame / dt;
+            float coeff = dt_from_last_frame / dt;
             
             vec4 previous_frame_position = previous_frame_sourcematrix * vec4(particle_position_initial, 1.0);
             vec4 current_frame_position  = sourcematrix * vec4(particle_position_initial, 1.0);
             
-            vec4 updated_initialposition  = mix(previous_frame_position,
-                                                current_frame_position,
-                                                coeff);
+            vec4 updated_initialposition = mix(current_frame_position,
+                                               previous_frame_position,
+                                               coeff);
                                                 
-            vec4 updated_initial_velocity = mix(previous_frame_sourcematrix * vec4(particle_velocity_initial, 0.0),
-                                                sourcematrix * vec4(particle_velocity_initial, 0.0),
-                                                coeff) ; //TODO: add emitter speed
+            vec4 updated_initial_velocity = mix(sourcematrix * vec4(particle_velocity_initial, 0.0),
+                                                previous_frame_sourcematrix * vec4(particle_velocity_initial, 0.0),
+                                                coeff);
                                           //+ (current_frame_position - previous_frame_position) / dt;
+            //To be accurate, emitter speed should be added.
+            //But the simple formula ( (current_frame_position - previous_frame_position) / dt ) with a constant speed
+            //between 2 frames creates visual artifacts when the framerate is low, and a more accurate formula would need
+            //more complex computations.
                                                 
             new_particle_position = updated_initialposition.xyz + dt_from_last_frame * updated_initial_velocity.xyz;
             new_particle_velocity = updated_initial_velocity.xyz;

src/graphics/gpu_particles.hpp

@@ -40,7 +40,7 @@ protected:
     float m_color_to[3];
     bool m_first_execution;
     bool m_randomize_initial_y;
-
+    
     GLuint texture;
     
     /** Previous frame particles emitter source matrix */

src/karts/kart.cpp

@@ -2605,9 +2605,8 @@ void Kart::updateGraphics(float dt, const Vec3& offset_xyz,
         // the normal maximum speed of the kart.
         if(nitro_frac>1.0f) nitro_frac = 1.0f;
     }
-    // speed * dt is the new size of the box in which particles start
-    m_kart_gfx->updateNitroGraphics(nitro_frac, getSpeed()*dt);
-
+    m_kart_gfx->updateNitroGraphics(nitro_frac);
+    
     // Handle leaning of karts
     // -----------------------
     // Note that we compare with maximum speed of the kart, not

src/karts/kart_gfx.cpp

@@ -350,11 +350,10 @@ void KartGFX::update(float dt)
 }  // update
 
 // ----------------------------------------------------------------------------
-/** Updates nitro dependent particle effects (and box sizes).
+/** Updates nitro dependent particle effects.
  *  \param nitro_frac Nitro fraction/
- *  \param new_size New size of the box in which new particles are emitted.
  */
-void KartGFX::updateNitroGraphics(float nitro_frac, float new_size)
+void KartGFX::updateNitroGraphics(float nitro_frac)
 {
     // Upate particle effects (creation rate, and emitter size
     // depending on speed)
@@ -375,11 +374,6 @@ void KartGFX::updateNitroGraphics(float nitro_frac, float new_size)
         setCreationRateAbsolute(KartGFX::KGFX_NITROSMOKE2, 0);
         m_nitro_light->setVisible(false);
     }
-    resizeBox(KartGFX::KGFX_NITRO1,      new_size);
-    resizeBox(KartGFX::KGFX_NITRO2,      new_size);
-    resizeBox(KartGFX::KGFX_NITROSMOKE1, new_size);
-    resizeBox(KartGFX::KGFX_NITROSMOKE2, new_size);
-    resizeBox(KartGFX::KGFX_ZIPPER,      new_size);
 
 }  // updateGraphics
 

src/karts/kart_gfx.hpp

@@ -99,7 +99,7 @@ public:
     void setCreationRateRelative(const KartGFXType type, float f);
     void updateTerrain(const ParticleKind *pk);
     void update(float dt);
-    void updateNitroGraphics(float f, float new_size);
+    void updateNitroGraphics(float f);
     void updateSkidLight(unsigned int level);
 
 };   // KartWGFX