From c2b252658712435b3d480d498cfdb2997b9a7452 Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Tue, 3 Mar 2026 19:44:09 +0100
Subject: [PATCH] map rendering: wip coordinate system screen -> world and
 world -> screen

screen to world is still broken, but there are (failing) test cases :^)
---
 src/r_assets.c     |  2 +-
 src/t_camera.c     |  4 +---
 src/test.c         |  1 +
 src/tests/t_math.c | 21 +++++++++++++++++++--
 src/u_math.c       | 14 +++++++++-----
 src/u_math.h       |  7 +++++--
 6 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/src/r_assets.c b/src/r_assets.c
index 05588a2..6661eab 100644
--- a/src/r_assets.c
+++ b/src/r_assets.c
@@ -64,7 +64,7 @@ void r_draw_solid_isometric_tile(i32 x, i32 y, r_color color) {
 	
 	/* draw a tile texture from origin */
 	for (i = 0; i < R_TILE_W; i++) {
-		for (j = 0; j < R_TILE_H-1; j++) {
+		for (j = 0; j < R_TILE_H; j++) {
 			final_color = r_asset_fallback_tile[i + j * R_TILE_W] & color;
 			r_draw_pixel(&r_framebuffer, t.x + i, t.y + j, final_color);
 		}
diff --git a/src/t_camera.c b/src/t_camera.c
index 896dd79..3e2a830 100644
--- a/src/t_camera.c
+++ b/src/t_camera.c
@@ -24,9 +24,7 @@ lrts_bool t_camera_is_visible_screen(struct t_camera *c, i32 x, i32 y) {
 }
 
 lrts_bool t_camera_is_visible_world(struct t_camera *c, i32 x, i32 y) {
-	struct u_vec2 t;
-	t.x = c->x;
-	t.y = c->y;
+	struct u_vec2 t = u_point_to_screen(c->x, c->y);
 	
 	return u_point_in_rect(x, y, t.x, t.y, t.x + c->viewport_x, t.y + c->viewport_y);
 }
diff --git a/src/test.c b/src/test.c
index 3e11b59..9482ffe 100644
--- a/src/test.c
+++ b/src/test.c
@@ -31,6 +31,7 @@ int main(int argc, char **argv) {
 	T_TESTCASE("argv", t_test_argv);
 	T_TESTCASE("arena", t_test_arena);
 	T_TESTCASE("tile-to-screen", t_test_tile_to_screen);
+	T_TESTCASE("point-to-screen", t_test_point_to_world_world_to_point);
 	T_TESTCASE("point-in-rect", t_test_pointinrect);
 	T_TESTCASE("fixed-point-macro", t_test_fp_macros);
 	T_TESTCASE("fixed-point-sqrt", t_test_fp_sqrt);
diff --git a/src/tests/t_math.c b/src/tests/t_math.c
index 3e4e406..8323229 100644
--- a/src/tests/t_math.c
+++ b/src/tests/t_math.c
@@ -14,10 +14,27 @@ int t_test_tile_to_screen(void) {
 	T_ASSERT(res.x == 0 && res.y == 0, ("tile to screen %d/%d\n", res.x, res.y));
 
 	res = u_tile_to_screen(1, 1);
-	T_ASSERT(res.x == 96 && res.y == 0, ("tile to screen %d/%d\n", res.x, res.y));
+	T_ASSERT(res.x == 0 && res.y == 48, ("tile to screen %d/%d\n", res.x, res.y));
 
 	res = u_tile_to_screen(1, 2);
-	T_ASSERT(res.x == 144 && res.y == 24, ("tile to screen %d/%d\n", res.x, res.y));
+	T_ASSERT(res.x == -48 && res.y == 72, ("tile to screen %d/%d\n", res.x, res.y));
+	return 0;
+}
+
+int t_test_point_to_world_world_to_point(void) {
+	struct u_vec2 res = u_point_to_screen(1, 2);
+	T_ASSERT(res.x == -2 && res.y == 1, ("point to screen %d/%d\n", res.x, res.y));
+	
+	res = u_point_to_world(res.x, res.y);
+	T_ASSERT(res.x == 1 && res.y == 2, ("point to world %d/%d\n", res.x, res.y));
+
+
+	res = u_point_to_screen(32, 64);
+	T_ASSERT(res.x == -48 && res.y == 40, ("point to screen %d/%d\n", res.x, res.y));
+
+	res = u_point_to_world(res.x, res.y);
+	T_ASSERT(res.x == 32 && res.y == 64, ("point to world %d/%d\n", res.x, res.y));
+
 	return 0;
 }
 
diff --git a/src/u_math.c b/src/u_math.c
index e4c40a6..4ddfb88 100644
--- a/src/u_math.c
+++ b/src/u_math.c
@@ -11,19 +11,23 @@ struct u_vec2 u_vec2_mul(i32 n, struct u_vec2 v) {
 }
 
 struct u_vec2 u_tile_to_screen(i32 x, i32 y) {
+	return u_point_to_screen(x * R_TILE_W, y * R_TILE_H); 
+}
+
+struct u_vec2 u_point_to_screen(i32 x, i32 y) {
 	struct u_vec2 r;
 
-	r.x = (x * R_TILE_W / 2) + (y * R_TILE_W / 2);
-	r.y = (y * R_TILE_H / 2) - (x * R_TILE_H / 2);
+	r.x = (x / 2 - y);
+	r.y = (y + x / 2) / 2;
 
 	return r;
 }
 
-struct u_vec2 u_point_to_screen(i32 x, i32 y) {
+struct u_vec2 u_point_to_world(i32 x, i32 y) {
 	struct u_vec2 r;
 
-	r.x = (x) + (y);
-	r.y = (y) - (x);
+	r.x = (y + x);
+	r.y = (2 * y - x) / 2;
 
 	return r;
 }
diff --git a/src/u_math.h b/src/u_math.h
index af63f6c..5dc7678 100644
--- a/src/u_math.h
+++ b/src/u_math.h
@@ -45,14 +45,17 @@ struct u_vec2 {
 struct u_vec2 u_vec2_mul(i32 n, struct u_vec2 v);
 
 /*
- * converts a tile position to
+ * converts a world tile position to
  * a screen position
  */
 struct u_vec2 u_tile_to_screen(i32 x, i32 y);
 
-/* convers a point to screen space */
+/* convers a world point to screen space */
 struct u_vec2 u_point_to_screen(i32 x, i32 y);
 
+/* converts a screen point to world space */
+struct u_vec2 u_point_to_world(i32 x, i32 y);
+
 /* tests if a point is contained inside a rectangle */
 lrts_bool u_point_in_rect(i32 x, i32 y, i32 rx, i32 ry, i32 rw, i32 rh);
 
-- 
2.30.2