Add random jitter to fire

main.c

@@ -3,10 +3,15 @@
 
 #include <linux/input-event-codes.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/select.h>
+#include <sys/time.h>
 
 #define SHIP 0
+
 #define FIRE 1
+#define FIRE_MEAN -0.15
+#define FIRE_JITTER 0.01
 
 #define LIN_PWR 0.0001
 #define ROT_PWR 0.002
@@ -48,9 +53,9 @@ static shape_t shapes[MAX_SHAPES] = {
 		.entity = SHIP,
 		.vert_count = 3,
 		.verts = {
+			{ 0.0, -0.15 },
 			{ 0.015, -0.07 },
 			{ -0.015, -0.07 },
-			{ 0.0, -0.15 },
 		},
 	},
 };
@@ -59,6 +64,8 @@ static entity_t entities[MAX_ENTITIES] = {
 	{ .dir = { { 1, 0 }, { 0, 1 } } },
 };
 
+static mat3_t transforms[MAX_ENTITIES];
+
 static unsigned shape_count = 2;
 static unsigned entity_count = 1;
 static float aspect;
@@ -121,6 +128,11 @@ static mat3_t entity_transform(unsigned id)
 	return mat3_mul_mat3(mat3_translation(e->pos), mat2_extend(e->dir));
 }
 
+static float rand_plusminus()
+{
+	return 2.0f * ((float)rand() / RAND_MAX - 0.5f);
+}
+
 static void ship_update()
 {
 	entity_t *ship = entities + SHIP;
@@ -132,6 +144,7 @@ static void ship_update()
 	ship->vel = vec2_add(ship->vel, acc);
 
 	shapes[FIRE].visible = input.fwd != 0;
+	shapes[FIRE].verts[0].y = FIRE_MEAN + FIRE_JITTER * rand_plusminus();
 }
 
 static void update()
@@ -152,15 +165,13 @@ static void update()
 			e->pos.x -= 2 * aspect;
 		else if (e->pos.x < -aspect)
 			e->pos.x += 2 * aspect;
+
+		transforms[i] = entity_transform(i);
 	}
 }
 
 static void draw()
 {
-	static mat3_t transforms[MAX_ENTITIES];
-	for (unsigned i = 0; i < entity_count; ++i)
-		transforms[i] = entity_transform(i);
-
 	for (unsigned i = 0; i < shape_count; ++i) {
 		if (!shapes[i].visible)
 			continue;
@@ -172,6 +183,10 @@ static void draw()
 
 int main()
 {
+	struct timeval tv;
+	gettimeofday(&tv, NULL);
+	srand(tv.tv_usec);
+
 	const int input_fd = input_init();
 	input_on_press(key_press_callback);
 	input_on_release(key_release_callback);