From b15cc1304d4ec8c08183a7fd142c7d502a208239 Mon Sep 17 00:00:00 2001
From: Andreas Ortmann <ortmann@finf.uni-hannover.de>
Date: Thu, 29 Sep 2016 09:32:56 +0200
Subject: [PATCH] adding nice trace-fadeout.

---
 .../renderer_polygon_3d.cpp                   |  8 +++++--
 game/state/state.cpp                          | 20 ++++++++++++++++++
 game/state/state.hpp                          |  1 +
 game/state/trace.cpp                          | 21 ++++++++++---------
 game/state/trace.hpp                          |  5 ++++-
 5 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/game/renderer_polygon_3d/renderer_polygon_3d.cpp b/game/renderer_polygon_3d/renderer_polygon_3d.cpp
index 4b8e066..86e650c 100644
--- a/game/renderer_polygon_3d/renderer_polygon_3d.cpp
+++ b/game/renderer_polygon_3d/renderer_polygon_3d.cpp
@@ -263,9 +263,13 @@ namespace endofthejedi {
         glUseProgram(0);
 
         glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
-        glColor3f(0.0, 0.0, 1.0);
-
         for (const game::Trace *trace : m_state->traces) {
+            float fade_out = 1.0;
+            if (trace->missile == nullptr) {
+                fade_out = 1.0 - (trace->age / trace->maxAge);
+            }
+
+            glColor3f(0.0, 0.3/fade_out, 1.0/fade_out);
             glBegin(GL_LINE_STRIP);
             for (const game::Trace::TracePoint &tp : trace->points) {
                 glVertex2f(tp.position.x, tp.position.y);
diff --git a/game/state/state.cpp b/game/state/state.cpp
index d34915f..12edaa6 100644
--- a/game/state/state.cpp
+++ b/game/state/state.cpp
@@ -262,6 +262,8 @@ namespace game {
 
         advanceExplosions(dt);
 
+        advanceTraceAges(dt);
+
         advancePlayerCommands(dt);
 
         advancePlayerMissiles(dt);
@@ -356,4 +358,22 @@ namespace game {
 
         explosions.push_back(new Explosion(evt->position, evt->hit));
     }
+
+    void State::advanceTraceAges(float dt)
+    {
+        std::vector<Trace*> rm;
+        for (Trace *trace : traces) {
+            if (trace->missile == nullptr) {
+                trace->age += dt;
+                if (trace->age >= trace->maxAge) {
+                    rm.push_back(trace);
+                }
+            }
+        }
+
+        for (Trace *trace : rm) {
+            traces.remove(trace);
+            delete(trace);
+        }
+    }
 }
diff --git a/game/state/state.hpp b/game/state/state.hpp
index d952cca..eef029e 100644
--- a/game/state/state.hpp
+++ b/game/state/state.hpp
@@ -101,6 +101,7 @@ namespace game {
 
         void addExplosionFromHit(const Missile::Event *evt);
 
+        void advanceTraceAges(float dt);
         void advanceExplosions(float dt);
         void advancePlayerShipSpawns(float dt);
         void advancePlayerCommands(float dt);
diff --git a/game/state/trace.cpp b/game/state/trace.cpp
index 0b51695..3739cdf 100644
--- a/game/state/trace.cpp
+++ b/game/state/trace.cpp
@@ -13,24 +13,25 @@ namespace game {
     {
     }
 
+    Trace::Trace(Missile *missile, float maxAge)
+        : missile(missile)
+        , player(missile->player)
+        , fidelityCounter(0)
+        , age(0.0)
+        , maxAge(maxAge)
+    {
+        points.push_back(TracePoint(missile));
+    }
+
     Trace::~Trace()
     {
         //std::cout<<"~Trace()" << std::endl;
     }
 
-    Trace::Trace(Missile *missile)
-        : missile(missile)
-        , player(missile->player)
-        , fidelityCounter(0)
-        , age(0.0)
-    {
-        points.push_back(TracePoint(missile));
-    }
-
     void Trace::addPointFromMissile(bool forceAdd)
     {
         fidelityCounter++;
-        if (forceAdd || fidelityCounter >= 10) {
+        if (forceAdd || fidelityCounter >= 20) {
             fidelityCounter = 0;
             points.push_back(TracePoint(missile));
         }
diff --git a/game/state/trace.hpp b/game/state/trace.hpp
index 2b4f4f0..7edfbaf 100644
--- a/game/state/trace.hpp
+++ b/game/state/trace.hpp
@@ -13,7 +13,7 @@ namespace game {
      */
     class Trace {
         public:
-            Trace(Missile *missile);
+            Trace(Missile *missile, float maxAge=5.0);
             ~Trace();
 
             // Add the current position of the missile as a new point on the
@@ -51,6 +51,9 @@ namespace game {
 
             // age of the trace. if too old, it can be removed to save
             // space/power
+            // ageing starts when the trace is finished.
             float age;
+
+            float maxAge;
     };
 }