Frametime-independent dynamics.

1 files changed, 10 insertions, 5 deletions

diff --git a/src/common.hpp b/src/common.hpp
index f89ae08..df14f6f 100644
--- a/src/common.hpp
+++ b/src/common.hpp
@@ -175,7 +175,7 @@ namespace game {
 	class unit_t;
 
 	class state_t {
-		double now;
+		double now, dt;
 
 		std::unordered_set<unit_t*> units;
 		std::unordered_set<unit_t*> selected_units;
@@ -185,7 +185,7 @@ namespace game {
 
 		void start(void);
 		void stop(void);
-		void tick(double now_);
+		void tick(double now_, double dt_);
 
 		// These are called by the interface.
 		void select(rectf_t rect);
@@ -213,7 +213,7 @@ namespace interface {
 
 	public:
 		state_t(sf::RenderWindow *window_, game::state_t *game);
-		void tick(void);
+		void tick(double dt);
 		void render_to(render::state_t *render);
 	};
 }
@@ -264,10 +264,10 @@ namespace render {
 		void drender_text(rectf_t rect, std::string str);
 		void drender_entity(world::entity_t *ent);
 	public:
-		double now;
+		double now, dt;
 
 		state_t(sf::RenderWindow *window_);
-		void begin_frame(double time_);
+		void begin_frame(double time_, double dt_);
 		void end_frame(void);
 		void render(game::state_t *game);
 		void render(animated_texture_t *anim, rectf_t bounds, bool mirror = false);
@@ -333,3 +333,8 @@ T bilerp(T a, T b, T c, T d, T x, T y)
 	cd = lerp(c, d, x);
 	return lerp(ab, cd, y);
 }
+
+static inline float expfade(float a, float b, float l, float dt)
+{
+	return b + (a - b) * exp(-l * dt);
+}