interceptmarker.patch

Index: src/gfx/cockpit.cpp
===================================================================
--- src/gfx/cockpit.cpp (revision 13600)
+++ src/gfx/cockpit.cpp (working copy)
@@ -522,6 +522,70 @@
     GFXDisable( SMOOTH );
 }

+inline void DrawInterceptMarker( Unit * player, QVector p, QVector q, QVector r )
+{
+    static const float scale = XMLSupport::parse_float( vs_config->getVariable( "graphics", "hud", "min_target_box_size", ".01" ) );
+    const Unit * target = player->Target();
+
+    // ray-sphere intersection r^2 = (vp * t)^2
+    // (vt * vt) * t^2 + (2 * vt * loc) * t + (loc * loc) - (vp * vp) * t^2 = 0
+    QVector loc = target->Position() - _Universe->AccessCamera()->GetPosition();
+    Vector vt = target->GetVelocity();
+    Vector vp = player->GetVelocity();
+    float a = vt.Dot( vt ) - vp.Dot( vp );
+    float b = 2 * vt.Dot( loc );
+    float c = loc.Dot( loc );
+    float d = b * b - 4 * a * c;
+    if ( d < 0 || fabs(a) < 1E-6 )
+        return;
+
+    float ds = sqrtf( d );
+    float s = (b < 0) ? 0.5f * ( -b - ds ) : 0.5f * ( -b + ds );
+    float t0 = s / a;
+    float t1 = c / s;
+
+    // get minimal positive time
+    float t = t0 > 0 ? (t1 > t0 ? t0 : t1) : (t1 > 0 ? t1 : 0);
+
+    // dont't draw marker if we are a half second away from target
+    if (t < 0.5f)
+        return;
+
+    // calculate marker position
+    QVector locn = loc / loc.Magnitude();          // normal towards target
+    QVector locv = vt * t;                         // target travel vector
+    QVector locp = locv - locn * locn.Dot( locv ); // projected target travel vector
+    QVector loct = loc + locp;                     // interception marker position in space
+
+    // enforce min marker size
+    float size = target->rSize();
+    float minsize = loct.Magnitude() * scale;
+    if (size < minsize)
+        size = minsize;
+
+    // fade out marker when close to target box
+    float alpha = std::min(1.0, 0.2 * locp.MagnitudeSquared() / (size * size));
+
+    GFXEnable( SMOOTH );
+    GFXBlendMode( SRCALPHA, INVSRCALPHA );
+    GFXColor4f( 1, 1, 1, alpha );
+    const QVector v[4] = {
+        loct + p*size + q*size,
+        loct - p*size - q*size,
+        loct - p*size + q*size,
+        loct + p*size - q*size,
+    };
+    const float verts[4 * 3] = {
+        v[0].x, v[0].y, v[0].z,
+        v[1].x, v[1].y, v[1].z,
+        v[2].x, v[2].y, v[2].z,
+        v[3].x, v[3].y, v[3].z,
+    };
+    GFXDraw( GFXLINE, verts, 4 );
+    GFXColor4f( 1, 1, 1, 1 );
+    GFXDisable( SMOOTH );
+}
+
 void GameCockpit::DrawTargetBox(const Radar::Sensor& sensor)
 {
     if (sensor.InsideNebula())
@@ -576,6 +640,8 @@
         }
         GFXDisable( SMOOTH );
     }
+    if (draw_intercept_marker)
+        DrawInterceptMarker( player, CamP, CamQ, CamR );
     static bool draw_target_nav_symbol =
         XMLSupport::parse_bool( vs_config->getVariable( "graphics", "draw_target_nav_symbol", "true" ) );
     static bool draw_jump_nav_symbol   =
@@ -1851,7 +1917,8 @@
     for (i = 0; i < UnitImages< void >::NUMGAUGES; i++)
         gauges[i] = NULL;
     radarSprites[0] = radarSprites[1] = Pit[0] = Pit[1] = Pit[2] = Pit[3] = NULL;
-
+    static bool st_draw_intercept_marker =
+        XMLSupport::parse_bool( vs_config->getVariable( "graphics", "hud", "drawTargetInterceptPoint", "true" ) );
     static bool st_draw_all_boxes =
         XMLSupport::parse_bool( vs_config->getVariable( "graphics", "hud", "drawAllTargetBoxes", "false" ) );
     static bool st_draw_line_to_target =
@@ -1863,6 +1930,7 @@
     static bool st_always_itts = XMLSupport::parse_bool( vs_config->getVariable( "graphics", "hud", "drawAlwaysITTS", "false" ) );
     static bool st_steady_itts = XMLSupport::parse_bool( vs_config->getVariable( "physics", "steady_itts", "false" ) );

+    draw_intercept_marker = st_draw_intercept_marker;
     draw_all_boxes = st_draw_all_boxes;
     draw_line_to_target = st_draw_line_to_target;
     draw_line_to_targets_target = st_draw_line_to_targets_target;
Index: src/gfx/cockpit.h
===================================================================
--- src/gfx/cockpit.h   (revision 13600)
+++ src/gfx/cockpit.h   (working copy)
@@ -101,6 +101,8 @@
     Gauge     *gauges[UnitImages < void > ::NUMGAUGES];
     ///holds misc panels.  Panel[0] is always crosshairs (and adjusted to be in center of view screen, not cockpit)
     std::vector< VSSprite* >Panel;
+    ///draw target intercept point marker
+    bool     draw_intercept_marker;
     ///flag to decide whether to draw all target boxes
     bool     draw_all_boxes;
     bool     draw_line_to_target, draw_line_to_targets_target;