From b1d00741ee2c0b92b07e47b25fbd949061cc4a53 Mon Sep 17 00:00:00 2001
From: luboslenco <lubos.lenco@gmail.com>
Date: Tue, 2 Jun 2026 19:36:16 +0200
Subject: [PATCH] paint: atlas fixes

---
 paint/sources/export_texture.c | 35 +++++++++++++++++++++++++++-------
 paint/sources/slot_layer.c     |  2 +-
 paint/sources/util_uv.c        |  2 +-
 3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/paint/sources/export_texture.c b/paint/sources/export_texture.c
index 9176e753..b443e830 100644
--- a/paint/sources/export_texture.c
+++ b/paint/sources/export_texture.c
@@ -558,18 +558,39 @@ void export_texture_run(char *path, bool bake_material) {
 			}
 		}
 		if (atlas_export) {
+			string_array_t *used_atlases = project_get_used_atlases();
 			for (i32 atlas_index = 0; atlas_index < project_atlas_objects->length; ++atlas_index) {
-				slot_layer_t_array_t *layers = any_array_create_from_raw((void *[]){}, 0);
+				// Skip atlases that no object is assigned to
+				bool atlas_used = false;
 				for (i32 object_index = 0; object_index < project_atlas_objects->length; ++object_index) {
 					if (project_atlas_objects->buffer[object_index] == atlas_index) {
-						for (i32 i = 0; i < project_layers->length; ++i) {
-							slot_layer_t *l = project_layers->buffer[i];
-							if (slot_layer_get_object_mask(l) == 0 || // shared object
-							    slot_layer_get_object_mask(l) - 1 == object_index) {
-								any_array_push(layers, l);
-							}
+						atlas_used = true;
+						break;
+					}
+				}
+				if (!atlas_used) {
+					continue;
+				}
+				slot_layer_t_array_t *layers = any_array_create_from_raw((void *[]){}, 0);
+				for (i32 i = 0; i < project_layers->length; ++i) {
+					slot_layer_t *l    = project_layers->buffer[i];
+					i32           mask = slot_layer_get_object_mask(l);
+					bool          add  = false;
+					if (mask == 0) { // Shared object
+						add = true;
+					}
+					else if (mask <= project_paint_objects->length) { // Specific object
+						add = project_atlas_objects->buffer[mask - 1] == atlas_index;
+					}
+					else if (used_atlases != NULL) { // Atlas
+						i32 used_index = mask - project_paint_objects->length - 1;
+						if (used_index < used_atlases->length) {
+							add = string_array_index_of(project_atlas_names, used_atlases->buffer[used_index]) == atlas_index;
 						}
 					}
+					if (add) {
+						any_array_push(layers, l);
+					}
 				}
 				if (layers->length > 0) {
 					export_texture_run_layers(path, layers, project_atlas_names->buffer[atlas_index], false);
diff --git a/paint/sources/slot_layer.c b/paint/sources/slot_layer.c
index e4377483..19a097b2 100644
--- a/paint/sources/slot_layer.c
+++ b/paint/sources/slot_layer.c
@@ -1330,7 +1330,7 @@ void layers_set_object_mask() {
 		context_select_paint_object(o);
 	}
 	else {
-		bool is_atlas = slot_layer_get_object_mask(g_context->layer) > 0 && slot_layer_get_object_mask(g_context->layer) <= project_paint_objects->length;
+		bool is_atlas = slot_layer_get_object_mask(g_context->layer) > project_paint_objects->length;
 		if (g_context->merged_object == NULL || is_atlas || g_context->merged_object_is_atlas) {
 			mesh_object_t_array_t *visibles = is_atlas ? project_get_atlas_objects(slot_layer_get_object_mask(g_context->layer)) : NULL;
 			util_mesh_merge(visibles);
diff --git a/paint/sources/util_uv.c b/paint/sources/util_uv.c
index 4daa5f8d..97fca963 100644
--- a/paint/sources/util_uv.c
+++ b/paint/sources/util_uv.c
@@ -26,7 +26,7 @@ void util_uv_cache_uv_map() {
 
 	util_uv_uvmap_cached  = true;
 	i32            mask   = slot_layer_get_object_mask(g_context->layer);
-	mesh_object_t *merged = mask > 0 ? project_paint_objects->buffer[mask - 1] : g_context->merged_object;
+	mesh_object_t *merged = (mask > 0 && mask <= project_paint_objects->length) ? project_paint_objects->buffer[mask - 1] : g_context->merged_object;
 	mesh_data_t   *mesh   = (g_context->layer_filter == 0 && merged != NULL) ? merged->data : g_context->paint_object->data;
 
 	i16_array_t *texa = mesh->vertex_arrays->buffer[2]->values;