From f58a21265296668ac239e1b2315bf4fc1767aa7b Mon Sep 17 00:00:00 2001
From: KikooDX <kikoodx@protonmail.com>
Date: Mon, 14 Sep 2020 10:33:01 +0200
Subject: [PATCH] [camera] lerping and miscelanious

---
 include/camera.h |  2 +-
 include/vec.h    |  6 +++++-
 src/camera.c     |  2 ++
 src/main.c       |  4 ++--
 src/vec.c        | 15 ++++++++++++---
 5 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/include/camera.h b/include/camera.h
index 517e04b..ee8a373 100644
--- a/include/camera.h
+++ b/include/camera.h
@@ -6,7 +6,7 @@
 typedef struct Camera
 {
 	Vec position;
-	Vec *follow; /* the target position to lerp on */
+	Vec *target; /* the target position to lerp on */
 	float speed; /* camera lerp speed with 0 < speed <= 1 */
 } Camera;
 
diff --git a/include/vec.h b/include/vec.h
index b7f63f9..6b93224 100644
--- a/include/vec.h
+++ b/include/vec.h
@@ -8,7 +8,7 @@ typedef struct Vec
 } Vec;
 
 /* like memcpy but for vectors */
-void vec_cpy(Vec *destination, Vec *source);
+void vec_cpy(Vec *destination, Vec source);
 
 /* apply a force on a vector */
 void vec_add(Vec *vector, Vec force);
@@ -22,4 +22,8 @@ void vec_mul(Vec *vector, float scale);
 /* divise a vector by a scale */
 void vec_div(Vec *vector, float scale);
 
+/* Linear interpolation between two vectors.
+ * Require a scale ranging from 0 to 1 (0 is instant, 1 is completly still). */
+void vec_lerp(Vec *from, Vec to, float scale);
+
 #endif /* _DEF_VEC */
diff --git a/src/camera.c b/src/camera.c
index 4589d27..90daef3 100644
--- a/src/camera.c
+++ b/src/camera.c
@@ -1,5 +1,7 @@
 #include "camera.h"
+#include "vec.h"
 
 void camera_step(Camera *camera)
 {
+	vec_lerp(&camera->position, *camera->target, camera->speed);
 }
diff --git a/src/main.c b/src/main.c
index c8ffd3d..b8959cb 100644
--- a/src/main.c
+++ b/src/main.c
@@ -26,9 +26,9 @@ int main(void)
 
 	/* create camera */
 	Camera camera = {
-		.follow = &player.position
+		.target = &player.position
 	};
-	vec_cpy(&camera.position, &player.position);
+	vec_cpy(&camera.position, player.position);
 
 	/* main game loop */
 	step_event(&player, &level, &camera);
diff --git a/src/vec.c b/src/vec.c
index af64294..a5a555c 100644
--- a/src/vec.c
+++ b/src/vec.c
@@ -1,9 +1,9 @@
 #include "vec.h"
 
-void vec_cpy(Vec *destination, Vec *source)
+void vec_cpy(Vec *destination, Vec source)
 {
-	destination->x = source->x;
-	destination->y = source->y;
+	destination->x = source.x;
+	destination->y = source.y;
 }
 
 void vec_add(Vec *vector, Vec force)
@@ -29,3 +29,12 @@ void vec_div(Vec *vector, float scale)
 	vector->x /= scale;
 	vector->y /= scale;
 }
+
+void vec_lerp(Vec *from, Vec to, float scale)
+{
+	Vec temp = {};
+	vec_cpy(&temp, to);
+	vec_sub(&temp, *from);
+	vec_mul(&temp, scale);
+	vec_add(from, temp);
+}