Smooth badguy and other object motion when frame prediction is on

This commit extrapolates the drawn position for badguys and some other
moving objects, making their motion look smoother when both the frame
rate is high and frame prediction is on. This is already being done for
Tux, but that is not enough to always produce the illusion of smooth
motion. Without this commit one can at high frame rates see choppy
motion on carried objects when Tux is running, and on quickly moving
badguys, like MrIceBlock.

Author: mstoeckl

src/badguy/badguy.cpp

@@ -31,6 +31,7 @@
 #include "object/water_drop.hpp"
 #include "sprite/sprite.hpp"
 #include "sprite/sprite_manager.hpp"
+#include "supertux/constants.hpp"
 #include "supertux/level.hpp"
 #include "supertux/sector.hpp"
 #include "supertux/tile.hpp"
@@ -141,10 +142,13 @@ BadGuy::draw(DrawingContext& context)
 {
   if (!m_sprite.get()) return;
 
+  Vector draw_offset = context.get_time_offset() * m_physic.get_velocity();
+  Vector draw_pos = get_pos() + draw_offset;
+
   if (m_state == STATE_INIT || m_state == STATE_INACTIVE)
   {
     if (Editor::is_active()) {
-      m_sprite->draw(context.color(), get_pos(), m_layer, m_flip);
+      m_sprite->draw(context.color(), draw_pos, m_layer, m_flip);
     }
   }
   else
@@ -153,27 +157,27 @@ BadGuy::draw(DrawingContext& context)
     {
       context.push_transform();
       context.set_flip(context.get_flip() ^ VERTICAL_FLIP);
-      m_sprite->draw(context.color(), get_pos(), m_layer, m_flip);
+      m_sprite->draw(context.color(), draw_pos, m_layer, m_flip);
       context.pop_transform();
     }
     else
     {
       if (m_unfreeze_timer.started() && m_unfreeze_timer.get_timeleft() <= 1.f)
       {
-        m_sprite->draw(context.color(), get_pos() + Vector(graphicsRandom.randf(-3, 3), 0.f), m_layer-1, m_flip);
+        m_sprite->draw(context.color(), draw_pos + Vector(graphicsRandom.randf(-3, 3), 0.f), m_layer - 1, m_flip);
         if (is_portable())
-          m_freezesprite->draw(context.color(), get_pos() + Vector(graphicsRandom.randf(-3, 3), 0.f), m_layer);
+          m_freezesprite->draw(context.color(), draw_pos + Vector(graphicsRandom.randf(-3, 3), 0.f), m_layer);
       }
       else
       {
         if (m_frozen && is_portable())
-          m_freezesprite->draw(context.color(), get_pos(), m_layer);
-        m_sprite->draw(context.color(), get_pos(), m_layer - (m_frozen ? 1 : 0), m_flip);
+          m_freezesprite->draw(context.color(), draw_pos, m_layer);
+        m_sprite->draw(context.color(), draw_pos, m_layer - (m_frozen ? 1 : 0), m_flip);
       }
 
       if (m_glowing)
       {
-        m_lightsprite->draw(context.light(), m_col.m_bbox.get_middle(), 0);
+        m_lightsprite->draw(context.light(), m_col.m_bbox.get_middle() + draw_offset, 0);
       }
     }
   }
@@ -892,6 +896,7 @@ BadGuy::grab(MovingObject& object, const Vector& pos, Direction dir_)
 {
   Portable::grab(object, pos, dir_);
   m_col.set_movement(pos - get_pos());
+  m_physic.set_velocity(m_col.get_movement() * LOGICAL_FPS);
   m_dir = dir_;
   if (m_frozen)
   {

src/badguy/crusher.cpp

@@ -468,14 +468,15 @@ Crusher::spawn_roots(Direction direction)
 void
 Crusher::draw(DrawingContext& context)
 {
-  m_sprite->draw(context.color(), get_pos(), m_layer + 2, m_flip);
+  Vector draw_pos = get_pos() + m_physic.get_velocity() * context.get_time_offset();
+  m_sprite->draw(context.color(), draw_pos, m_layer + 2, m_flip);
   if (m_sprite->has_action("whites"))
   {
     // Draw crusher's eyes slightly behind.
-    m_lefteye->draw(context.color(), get_pos() + eye_position(false), m_layer + 1, m_flip);
-    m_righteye->draw(context.color(), get_pos() + eye_position(true), m_layer + 1, m_flip);
+    m_lefteye->draw(context.color(), draw_pos + eye_position(false), m_layer + 1, m_flip);
+    m_righteye->draw(context.color(), draw_pos + eye_position(true), m_layer + 1, m_flip);
     // Draw the whites of crusher's eyes even further behind.
-    m_whites->draw(context.color(), get_pos(), m_layer, m_flip);
+    m_whites->draw(context.color(), draw_pos, m_layer, m_flip);
   }
 }
 

src/badguy/mrbomb.cpp

@@ -26,6 +26,7 @@
 #include "object/portable.hpp"
 #include "sprite/sprite.hpp"
 #include "sprite/sprite_manager.hpp"
+#include "supertux/constants.hpp"
 #include "supertux/sector.hpp"
 #include "util/reader_mapping.hpp"
 
@@ -242,6 +243,7 @@ MrBomb::grab(MovingObject& object, const Vector& pos, Direction dir_)
     set_action(dir_);
 
   m_col.set_movement(pos - get_pos());
+  m_physic.set_velocity(m_col.get_movement() * LOGICAL_FPS);
   m_dir = dir_;
   set_colgroup_active(COLGROUP_DISABLED);
 }

src/badguy/mriceblock.cpp

@@ -24,6 +24,7 @@
 #include "object/player.hpp"
 #include "object/portable.hpp"
 #include "sprite/sprite.hpp"
+#include "supertux/constants.hpp"
 #include "supertux/sector.hpp"
 
 namespace {
@@ -356,6 +357,7 @@ MrIceBlock::grab(MovingObject& object, const Vector& pos, Direction dir_)
 
   Portable::grab(object, pos, dir_);
   m_col.set_movement(pos - get_pos());
+  m_physic.set_velocity(m_col.get_movement() * LOGICAL_FPS);
   m_dir = dir_;
   set_action("flat", m_dir, /* loops = */ -1);
   set_state(ICESTATE_GRABBED);

src/badguy/rcrystallo.cpp

@@ -148,7 +148,8 @@ void
 RCrystallo::draw(DrawingContext& context)
 {
   context.push_transform();
-  m_sprite->draw(context.color(), get_pos(), m_layer);
+  Vector draw_pos = get_pos() + m_physic.get_velocity() * context.get_time_offset();
+  m_sprite->draw(context.color(), draw_pos, m_layer);
   context.pop_transform();
 }
 

src/badguy/snail.cpp

@@ -23,6 +23,7 @@
 #include "object/player.hpp"
 #include "object/portable.hpp"
 #include "sprite/sprite.hpp"
+#include "supertux/constants.hpp"
 #include "supertux/sector.hpp"
 
 namespace {
@@ -390,6 +391,7 @@ Snail::grab(MovingObject& object, const Vector& pos, Direction dir_)
   if (m_frozen)
     BadGuy::grab(object, pos, dir_);
   m_col.set_movement(pos - get_pos());
+  m_physic.set_velocity(m_col.get_movement() * LOGICAL_FPS);
   m_dir = dir_;
   if (!m_frozen)
   {

src/object/player.cpp

@@ -2017,6 +2017,7 @@ Player::draw(DrawingContext& context)
   // if Tux is above camera, draw little "air arrow" to show where he is x-wise
   if (m_col.m_bbox.get_bottom() - 16 < Sector::get().get_camera().get_translation().y) {
     float px = m_col.m_bbox.get_left() + (m_col.m_bbox.get_right() - m_col.m_bbox.get_left() - static_cast<float>(m_airarrow.get()->get_width())) / 2.0f;
+    px += context.get_time_offset() * m_physic.get_velocity().x;
     float py = Sector::get().get_camera().get_translation().y;
     py += std::min(((py - (m_col.m_bbox.get_bottom() + 16)) / 4), 16.0f);
     context.color().draw_surface(m_airarrow, Vector(px, py), LAYER_HUD - 1);

src/object/rock.cpp

@@ -24,6 +24,7 @@
 #include "object/lit_object.hpp"
 #include "object/pushbutton.hpp"
 #include "object/trampoline.hpp"
+#include "supertux/constants.hpp"
 #include "supertux/sector.hpp"
 #include "supertux/tile.hpp"
 #include "object/player.hpp"
@@ -229,6 +230,7 @@ Rock::grab(MovingObject& object, const Vector& pos, Direction dir_)
   Portable::grab(object, pos, dir_);
   Vector movement = pos - get_pos();
   m_col.set_movement(movement);
+  physic.set_velocity(movement * LOGICAL_FPS);
   last_movement = movement;
   set_group(COLGROUP_TOUCHABLE); //needed for lanterns catching willowisps
   on_ground = false;
@@ -272,6 +274,13 @@ Rock::ungrab(MovingObject& object, Direction dir)
   Portable::ungrab(object, dir);
 }
 
+void
+Rock::draw(DrawingContext& context)
+{
+  Vector offset = physic.get_velocity() * context.get_time_offset();
+  m_sprite->draw(context.color(), get_pos() + offset, m_layer, m_flip);
+}
+
 ObjectSettings
 Rock::get_settings()
 {

src/object/rock.hpp

@@ -44,6 +44,7 @@ class Rock : public MovingSprite,
   virtual ObjectSettings get_settings() override;
   virtual GameObjectTypes get_types() const override;
   std::string get_default_sprite_name() const override;
+  void draw(DrawingContext& context) override;
 
   /** Adds velocity from wind */
   virtual void add_wind_velocity(const Vector& velocity, const Vector& end_speed);

src/object/smoke_cloud.cpp

@@ -39,7 +39,8 @@ SmokeCloud::update(float dt_sec)
 void
 SmokeCloud::draw(DrawingContext& context)
 {
-  sprite->draw(context.color(), position, LAYER_OBJECTS + 1);
+  Vector draw_pos = position - Vector(0.0, 120.0) * std::min(context.get_time_offset(), timer.get_timeleft());
+  sprite->draw(context.color(), draw_pos, LAYER_OBJECTS + 1);
 }
 
 /* EOF */

src/object/sprite_particle.cpp

@@ -99,13 +99,14 @@ SpriteParticle::update(float dt_sec)
 void
 SpriteParticle::draw(DrawingContext& context)
 {
-  sprite->draw(context.color(), position, drawing_layer);
+  Vector draw_pos = position + velocity * context.get_time_offset();
+  sprite->draw(context.color(), draw_pos, drawing_layer);
 
   //Sparkles glow in the dark
   if (glow)
   {
-    sprite->draw(context.light(), position, drawing_layer);
-    lightsprite->draw(context.light(), position + Vector(12, 12), 0);
+    sprite->draw(context.light(), draw_pos, drawing_layer);
+    lightsprite->draw(context.light(), draw_pos + Vector(12, 12), 0);
   }
 
 }