platformer physics

CMakeLists.txt

@@ -11,6 +11,7 @@ include_directories(inc)
 
 set(SOURCES
 	src/main.c
+	src/util.c
 	src/draw.c
 	src/input.c
 	src/level.c

inc/conf.h

@@ -1,4 +1,13 @@
 #pragma once
 
-#define TILE_SIZE 16
-#define TILE_OOB  0
+#define TILE_SIZE           16
+#define PLAYER_WIDTH        12
+#define PLAYER_HEIGHT       12
+#define MAX_WALK_SPEED      2.0f
+#define AIR_ACCELERATION    0.4f
+#define GROUND_ACCELERATION 0.4f
+#define AIR_FRICTION        (AIR_ACCELERATION / MAX_WALK_SPEED)
+#define GROUND_FRICTION     (GROUND_ACCELERATION / MAX_WALK_SPEED)
+#define AIR_RESISTANCE      0.02f
+#define GRAVITY             0.2f
+#define JUMP_SPEED          -4.0f

inc/player.h

@@ -9,3 +9,4 @@ struct Player {
 void player_init(struct Player *);
 void player_update(struct Player *);
 void player_draw(struct Player *);
+void player_move(struct Player *, struct Vec);

inc/tile.h

@@ -0,0 +1,7 @@
+#pragma once
+
+enum Tile {
+	TILE_AIR,
+	TILE_SOLID,
+	TILE_OOB,
+};

inc/util.h

@@ -0,0 +1,3 @@
+#pragma once
+
+int sign(int);

src/level.c

@@ -1,5 +1,6 @@
 #include "level.h"
 #include "conf.h"
+#include "tile.h"
 #include "visual_data.h"
 #include <gint/display.h>
 #include <stdlib.h>

src/player.c

@@ -1,33 +1,118 @@
 #include "player.h"
+#include "conf.h"
 #include "draw.h"
+#include "input.h"
+#include "level.h"
+#include "tile.h"
+#include "util.h"
 
-static void player_reset_speed(struct Player *);
+static void reset_speed(struct Player *, int x, int y);
+static struct Vec update_rem(struct Player *);
+static int collide_margin(int x, int y, int tile, int margin);
+static int collide(int x, int y, int tile);
+static int collide_solid(int x, int y);
 
 void
 player_init(struct Player *p)
 {
-	p->pos.x = 0;
-	p->pos.y = 0;
-	player_reset_speed(p);
+	p->pos.x = TILE_SIZE;
+	p->pos.y = TILE_SIZE;
+	reset_speed(p, 1, 1);
 }
 
 void
 player_update(struct Player *p)
 {
-	p->pos.x++;
+	const int on_ground = collide_solid(p->pos.x, p->pos.y + 1);
+	const int k_left = input_down(K_LEFT);
+	const int k_right = input_down(K_RIGHT);
+	// const int k_up = input_down(K_UP);
+	// const int k_down = input_down(K_DOWN);
+	const int kp_jump = input_pressed(K_JUMP);
+	const int dir_x = k_right - k_left;
+
+	/* horizontal friction & acceleration */
+	p->spd.x *= on_ground ? (1 - GROUND_FRICTION) : (1 - AIR_FRICTION);
+	p->spd.x +=
+	    dir_x * (on_ground ? GROUND_ACCELERATION : AIR_ACCELERATION);
+
+	/* air resistance & gravity */
+	p->spd.y *= (1 - AIR_RESISTANCE);
+	p->spd.y += GRAVITY;
+
+	/* jump */
+	if (on_ground && kp_jump) p->spd.y = JUMP_SPEED;
+
+	player_move(p, update_rem(p));
 }
 
 void
 player_draw(struct Player *p)
 {
-	draw_rectangle(C_WHITE, p->pos.x, p->pos.y, 16, 16);
+	draw_rectangle(C_WHITE, p->pos.x, p->pos.y, PLAYER_WIDTH,
+	               PLAYER_HEIGHT);
+}
+
+void
+player_move(struct Player *p, struct Vec spd)
+{
+	float sign_x = sign(spd.x);
+	const float sign_y = sign(spd.y);
+	if (!sign_x && !sign_y) sign_x = 1.0f;
+
+	p->pos.x += spd.x;
+	if (collide_solid(p->pos.x, p->pos.y)) reset_speed(p, 1, 0);
+	while (collide_solid(p->pos.x, p->pos.y))
+		p->pos.x -= sign_x;
+
+	p->pos.y += spd.y;
+	if (collide_solid(p->pos.x, p->pos.y)) reset_speed(p, 0, 1);
+	while (collide_solid(p->pos.x, p->pos.y))
+		p->pos.y -= sign_y;
 }
 
 static void
-player_reset_speed(struct Player *p)
+reset_speed(struct Player *p, int x, int y)
 {
-	p->spd.x = 0.0f;
-	p->spd.y = 0.0f;
-	p->rem.x = 0.0f;
-	p->rem.y = 0.0f;
+	if (x) {
+		p->spd.x = 0.0f;
+		p->rem.x = 0.0f;
+	}
+	if (y) {
+		p->spd.y = 0.0f;
+		p->rem.y = 0.0f;
+	}
+}
+
+static struct Vec
+update_rem(struct Player *p)
+{
+	struct VecF spd_n_rem = {p->spd.x + p->rem.x, p->spd.y + p->rem.y};
+	struct Vec spd_trunc = {spd_n_rem.x, spd_n_rem.y};
+	p->rem.x = spd_n_rem.x - (float)spd_trunc.x;
+	p->rem.y = spd_n_rem.y - (float)spd_trunc.y;
+	return spd_trunc;
+}
+
+static int
+collide_margin(int x, int y, int tile, int margin)
+{
+	const int x1 = x + margin;
+	const int x2 = x + PLAYER_WIDTH - 1 - margin;
+	const int y1 = y + margin;
+	const int y2 = y + PLAYER_HEIGHT - 1 - margin;
+	return level_get_px(x1, y1) == tile || level_get_px(x2, y1) == tile ||
+	       level_get_px(x1, y2) == tile || level_get_px(x2, y2) == tile;
+}
+
+static int
+collide(int x, int y, int tile)
+{
+	return collide_margin(x, y, tile, 0);
+}
+
+static int
+collide_solid(int x, int y)
+{
+	return collide(x, y, TILE_SOLID);
 }

src/util.c

@@ -0,0 +1,7 @@
+#include "util.h"
+
+int
+sign(int x)
+{
+	return (x > 0) - (x < 0);
+}