From 3828d21f4a645bce864b81c59446a406a2a0623d Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Wed, 25 Feb 2026 05:23:01 +0100
Subject: [PATCH] rendering: wip asset fallback tile rendering

---
 src/lrts.c           |  3 +++
 src/p_r_sdl/p_init.c |  2 +-
 src/r_assets.c       | 21 ++++++++++++---------
 src/r_assets.h       |  4 +++-
 src/u_math.c         | 10 ++++++++++
 src/u_math.h         |  6 ++++++
 6 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/src/lrts.c b/src/lrts.c
index f10e157..ded1e9f 100644
--- a/src/lrts.c
+++ b/src/lrts.c
@@ -2,6 +2,7 @@
 #include "u_defs.h"
 #include "p_platform.h"
 #include "r_render.h"
+#include "r_assets.h"
 
 struct lrts_config lrts_global_cfg;
 
@@ -61,6 +62,8 @@ struct u_vec2 lrts_get_screen_res(void) {
 }
 
 void lrts_init(void) {
+	/* init the fallback tile mask */
+	r_asset_init_fallback_tile();
 }
 
 int lrts_main(int argc, char **argv) {
diff --git a/src/p_r_sdl/p_init.c b/src/p_r_sdl/p_init.c
index 41f2b13..572496b 100644
--- a/src/p_r_sdl/p_init.c
+++ b/src/p_r_sdl/p_init.c
@@ -34,7 +34,7 @@ int p_render_init(void) {
 
 int p_render_init_framebuffer(void) {
 	struct u_vec2 target_res = lrts_get_render_res();
-	r_target = SDL_CreateSurface(target_res.x, target_res.y, SDL_PIXELFORMAT_RGBX8888);
+	r_target = SDL_CreateSurface(target_res.x, target_res.y, SDL_PIXELFORMAT_RGBA8888);
 	if (r_target == LRTS_NULL) {
 		u_log(U_LOG_ERR, "Failed to create surface: %s\n", SDL_GetError());
 		exit(-1);
diff --git a/src/r_assets.c b/src/r_assets.c
index 902f2fc..724f3dc 100644
--- a/src/r_assets.c
+++ b/src/r_assets.c
@@ -1,26 +1,29 @@
 #include "r_assets.h"
 #include "r_render.h"
+#include "u_mem.h"
 
-#define R_SOLID_TILE_OUTLINE_COLOR 0xFF0000FF
+i32 r_asset_fallback_tile[R_TILE_W * R_TILE_H];
 
-void r_draw_solid_isometric_tile(i32 x, i32 y, r_color color, r_color outline_color) {
+void r_asset_init_fallback_tile(void) {
+	u_memset(r_asset_fallback_tile, 0, R_TILE_W * R_TILE_H);
+}
+
+void r_draw_solid_isometric_tile(i32 x, i32 y, r_color color) {
 	u32 i = 0;
 	u32 j = 0;
-	i32 ox = 0;
-	i32 oy = 0;
+	r_color final_color;
+	struct u_vec2 t = u_tile_to_screen(x, y);
 
 	/* converted origin point in isometric space */
-	ox = (x * R_TILE_W / 2) + (y * R_TILE_W / 2);;
-	oy = (y * R_TILE_H / 2) - (x * R_TILE_H / 2);
 
-	LRTS_UNUSED(outline_color);
 	LRTS_UNUSED(x);
 	LRTS_UNUSED(y);
 	
 	/* draw a tile texture from origin */
 	for (i = 0; i < R_TILE_W; i++) {
 		for (j = 1; j < R_TILE_H-1; j++) {
-			r_draw_pixel(&r_framebuffer, ox, oy, color);
+			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);
 		}
 	}
 }
@@ -30,7 +33,7 @@ void r_draw_tile(struct t_tile *t, i32 x, i32 y) {
 		case T_TILE_TYPE_NONE:
 			break;
 		case T_TILE_TYPE_GRASS:
-			r_draw_solid_isometric_tile(x, y, 0x44FF00FF, R_SOLID_TILE_OUTLINE_COLOR);
+			r_draw_solid_isometric_tile(x, y, 0x44FF00FF);
 			break;
 	}
 }
diff --git a/src/r_assets.h b/src/r_assets.h
index 2da488f..986c3b6 100644
--- a/src/r_assets.h
+++ b/src/r_assets.h
@@ -18,11 +18,13 @@
 #include "u_defs.h"
 
 /* 
- * Draws a tile to the frame buffer at x, y.
+ * Draws a tile to the frame buffer at tile position x, y.
  * Attempts to load the tile from the tile sheet
  * if no tile sheet is availabel a fallback is drawn instead
  */
 void r_draw_tile(struct t_tile *t, i32 x, i32 y);
 
+void r_asset_init_fallback_tile(void);
+
 
 #endif
diff --git a/src/u_math.c b/src/u_math.c
index a9ceaa2..c661829 100644
--- a/src/u_math.c
+++ b/src/u_math.c
@@ -1,4 +1,5 @@
 #include "u_math.h"
+#include "r_assets.h"
 
 struct u_fp u_fp_add(struct u_fp a, struct u_fp b) {
 	struct u_fp c = U_FP(0, 0);
@@ -53,3 +54,12 @@ struct u_vec2 u_vec2_mul(i32 n, struct u_vec2 v) {
 		
 	return r;
 }
+
+struct u_vec2 u_tile_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);
+
+	return r;
+}
diff --git a/src/u_math.h b/src/u_math.h
index 2aa2374..b5838f4 100644
--- a/src/u_math.h
+++ b/src/u_math.h
@@ -42,6 +42,12 @@ struct u_fp u_fp_mod(struct u_fp a, struct u_fp b);
  */
 struct u_vec2 u_vec2_mul(i32 n, struct u_vec2 v);
 
+/*
+ * converts a tile position to
+ * a screen position
+ */
+struct u_vec2 u_tile_to_screen(i32 x, i32 y);
+
 /* Clamps an integer value between min and max */
 #define U_CLAMP(v, min, max) if (v < min) { v = min; } if (v > max) { v = max; }
 
-- 
2.30.2