Remove requirement to have vertex positions when creating a mesh. Meshes can now be constructed from an index buffer alone

3 files changed, 33 insertions, 15 deletions

diff --git a/servers/rendering/renderer_rd/storage_rd/mesh_storage.cpp b/servers/rendering/renderer_rd/storage_rd/mesh_storage.cpp
index 585c42b2d8..1516e5e4fd 100644
--- a/servers/rendering/renderer_rd/storage_rd/mesh_storage.cpp
+++ b/servers/rendering/renderer_rd/storage_rd/mesh_storage.cpp
@@ -327,8 +327,10 @@ void MeshStorage::mesh_add_surface(RID p_mesh, const RS::SurfaceData &p_surface)
 
 	bool use_as_storage = (p_surface.skin_data.size() || mesh->blend_shape_count > 0);
 
-	s->vertex_buffer = RD::get_singleton()->vertex_buffer_create(p_surface.vertex_data.size(), p_surface.vertex_data, use_as_storage);
-	s->vertex_buffer_size = p_surface.vertex_data.size();
+	if (p_surface.vertex_data.size()) {
+		s->vertex_buffer = RD::get_singleton()->vertex_buffer_create(p_surface.vertex_data.size(), p_surface.vertex_data, use_as_storage);
+		s->vertex_buffer_size = p_surface.vertex_data.size();
+	}
 
 	if (p_surface.attribute_data.size()) {
 		s->attribute_buffer = RD::get_singleton()->vertex_buffer_create(p_surface.attribute_data.size(), p_surface.attribute_data);
@@ -345,7 +347,7 @@ void MeshStorage::mesh_add_surface(RID p_mesh, const RS::SurfaceData &p_surface)
 	}
 
 	if (p_surface.index_count) {
-		bool is_index_16 = p_surface.vertex_count <= 65536;
+		bool is_index_16 = p_surface.vertex_count <= 65536 && p_surface.vertex_count > 0;
 
 		s->index_buffer = RD::get_singleton()->index_buffer_create(p_surface.index_count, is_index_16 ? RD::INDEX_BUFFER_FORMAT_UINT16 : RD::INDEX_BUFFER_FORMAT_UINT32, p_surface.index_data, false);
 		s->index_count = p_surface.index_count;
@@ -364,6 +366,8 @@ void MeshStorage::mesh_add_surface(RID p_mesh, const RS::SurfaceData &p_surface)
 		}
 	}
 
+	ERR_FAIL_COND_MSG(!p_surface.index_count && !p_surface.vertex_count, "Meshes must contain a vertex array, an index array, or both");
+
 	s->aabb = p_surface.aabb;
 	s->bone_aabbs = p_surface.bone_aabbs; //only really useful for returning them.
 
@@ -377,7 +381,11 @@ void MeshStorage::mesh_add_surface(RID p_mesh, const RS::SurfaceData &p_surface)
 			RD::Uniform u;
 			u.binding = 0;
 			u.uniform_type = RD::UNIFORM_TYPE_STORAGE_BUFFER;
-			u.append_id(s->vertex_buffer);
+			if (s->vertex_buffer.is_valid()) {
+				u.append_id(s->vertex_buffer);
+			} else {
+				u.append_id(default_rd_storage_buffer);
+			}
 			uniforms.push_back(u);
 		}
 		{
@@ -470,6 +478,7 @@ void MeshStorage::mesh_surface_update_vertex_region(RID p_mesh, int p_surface, i
 	ERR_FAIL_COND(!mesh);
 	ERR_FAIL_UNSIGNED_INDEX((uint32_t)p_surface, mesh->surface_count);
 	ERR_FAIL_COND(p_data.size() == 0);
+	ERR_FAIL_COND(mesh->surfaces[p_surface]->vertex_buffer.is_null());
 	uint64_t data_size = p_data.size();
 	const uint8_t *r = p_data.ptr();
 
@@ -527,7 +536,9 @@ RS::SurfaceData MeshStorage::mesh_get_surface(RID p_mesh, int p_surface) const {
 
 	RS::SurfaceData sd;
 	sd.format = s.format;
-	sd.vertex_data = RD::get_singleton()->buffer_get_data(s.vertex_buffer);
+	if (s.vertex_buffer.is_valid()) {
+		sd.vertex_data = RD::get_singleton()->buffer_get_data(s.vertex_buffer);
+	}
 	if (s.attribute_buffer.is_valid()) {
 		sd.attribute_data = RD::get_singleton()->buffer_get_data(s.attribute_buffer);
 	}
@@ -705,7 +716,9 @@ void MeshStorage::mesh_clear(RID p_mesh) {
 	ERR_FAIL_COND(!mesh);
 	for (uint32_t i = 0; i < mesh->surface_count; i++) {
 		Mesh::Surface &s = *mesh->surfaces[i];
-		RD::get_singleton()->free(s.vertex_buffer); //clears arrays as dependency automatically, including all versions
+		if (s.vertex_buffer.is_valid()) {
+			RD::get_singleton()->free(s.vertex_buffer); //clears arrays as dependency automatically, including all versions
+		}
 		if (s.attribute_buffer.is_valid()) {
 			RD::get_singleton()->free(s.attribute_buffer);
 		}
@@ -851,7 +864,7 @@ void MeshStorage::_mesh_instance_add_surface(MeshInstance *mi, Mesh *mesh, uint3
 	}
 
 	MeshInstance::Surface s;
-	if (mesh->blend_shape_count > 0 || (mesh->surfaces[p_surface]->format & RS::ARRAY_FORMAT_BONES)) {
+	if ((mesh->blend_shape_count > 0 || (mesh->surfaces[p_surface]->format & RS::ARRAY_FORMAT_BONES)) && mesh->surfaces[p_surface]->vertex_buffer_size > 0) {
 		//surface warrants transform
 		s.vertex_buffer = RD::get_singleton()->vertex_buffer_create(mesh->surfaces[p_surface]->vertex_buffer_size, Vector<uint8_t>(), true);
 
diff --git a/servers/rendering_server.cpp b/servers/rendering_server.cpp
index a54d4f0384..dcdc56d948 100644
--- a/servers/rendering_server.cpp
+++ b/servers/rendering_server.cpp
@@ -627,7 +627,7 @@ Error RenderingServer::_surface_set_data(Array p_arrays, uint32_t p_format, uint
 				const int *src = indices.ptr();
 
 				for (int i = 0; i < p_index_array_len; i++) {
-					if (p_vertex_array_len < (1 << 16)) {
+					if (p_vertex_array_len < (1 << 16) && p_vertex_array_len > 0) {
 						uint16_t v = src[i];
 
 						memcpy(&iw[i * 2], &v, 2);
@@ -836,9 +836,8 @@ void RenderingServer::mesh_surface_make_offsets_from_format(uint32_t p_format, i
 					break;
 				}
 				/* determine whether using 16 or 32 bits indices */
-				if (p_vertex_len >= (1 << 16)) {
+				if (p_vertex_len >= (1 << 16) || p_vertex_len == 0) {
 					elem_size = 4;
-
 				} else {
 					elem_size = 2;
 				}
@@ -909,8 +908,6 @@ Error RenderingServer::mesh_create_surface_data_from_arrays(SurfaceData *r_surfa
 		}
 	}
 
-	ERR_FAIL_COND_V((format & RS::ARRAY_FORMAT_VERTEX) == 0, ERR_INVALID_PARAMETER); // Mandatory
-
 	if (p_blend_shapes.size()) {
 		// Validate format for morphs.
 		for (int i = 0; i < p_blend_shapes.size(); i++) {
@@ -944,6 +941,12 @@ Error RenderingServer::mesh_create_surface_data_from_arrays(SurfaceData *r_surfa
 	uint32_t mask = (1 << ARRAY_MAX) - 1;
 	format |= (~mask) & p_compress_format; // Make the full format.
 
+	if ((format & RS::ARRAY_FORMAT_VERTEX) == 0 && !(format & RS::ARRAY_FLAG_USES_EMPTY_VERTEX_ARRAY)) {
+		ERR_PRINT("Mesh created without vertex array. This mesh will not be visible with the default shader. If using an empty vertex array is intentional, create the mesh with the ARRAY_FLAG_USES_EMPTY_VERTEX_ARRAY flag to silence this error.");
+		// Set the flag here after warning to suppress errors down the pipeline.
+		format |= RS::ARRAY_FLAG_USES_EMPTY_VERTEX_ARRAY;
+	}
+
 	int vertex_array_size = vertex_element_size * array_len;
 	int attrib_array_size = attrib_element_size * array_len;
 	int skin_array_size = skin_element_size * array_len;
@@ -1378,7 +1381,7 @@ Array RenderingServer::mesh_create_arrays_from_surface_data(const SurfaceData &p
 	Vector<uint8_t> attrib_data = p_data.attribute_data;
 	Vector<uint8_t> skin_data = p_data.skin_data;
 
-	ERR_FAIL_COND_V(vertex_data.size() == 0, Array());
+	ERR_FAIL_COND_V(vertex_data.size() == 0 && (p_data.format & RS::ARRAY_FORMAT_VERTEX), Array());
 	int vertex_len = p_data.vertex_count;
 
 	Vector<uint8_t> index_data = p_data.index_data;
diff --git a/servers/rendering_server.h b/servers/rendering_server.h
index a2fe9caf19..d04c62bfd2 100644
--- a/servers/rendering_server.h
+++ b/servers/rendering_server.h
@@ -244,7 +244,7 @@ public:
 
 	enum ArrayFormat {
 		/* ARRAY FORMAT FLAGS */
-		ARRAY_FORMAT_VERTEX = 1 << ARRAY_VERTEX, // Mandatory
+		ARRAY_FORMAT_VERTEX = 1 << ARRAY_VERTEX,
 		ARRAY_FORMAT_NORMAL = 1 << ARRAY_NORMAL,
 		ARRAY_FORMAT_TANGENT = 1 << ARRAY_TANGENT,
 		ARRAY_FORMAT_COLOR = 1 << ARRAY_COLOR,
@@ -262,17 +262,19 @@ public:
 
 		ARRAY_FORMAT_CUSTOM_BASE = (ARRAY_INDEX + 1),
 		ARRAY_FORMAT_CUSTOM_BITS = 3,
+		ARRAY_FORMAT_CUSTOM_MASK = 0x7,
 		ARRAY_FORMAT_CUSTOM0_SHIFT = (ARRAY_FORMAT_CUSTOM_BASE + 0),
 		ARRAY_FORMAT_CUSTOM1_SHIFT = (ARRAY_FORMAT_CUSTOM_BASE + ARRAY_FORMAT_CUSTOM_BITS),
 		ARRAY_FORMAT_CUSTOM2_SHIFT = (ARRAY_FORMAT_CUSTOM_BASE + ARRAY_FORMAT_CUSTOM_BITS * 2),
 		ARRAY_FORMAT_CUSTOM3_SHIFT = (ARRAY_FORMAT_CUSTOM_BASE + ARRAY_FORMAT_CUSTOM_BITS * 3),
 
-		ARRAY_FORMAT_CUSTOM_MASK = 0x7,
 		ARRAY_COMPRESS_FLAGS_BASE = (ARRAY_INDEX + 1 + 12),
 
 		ARRAY_FLAG_USE_2D_VERTICES = 1 << (ARRAY_COMPRESS_FLAGS_BASE + 0),
 		ARRAY_FLAG_USE_DYNAMIC_UPDATE = 1 << (ARRAY_COMPRESS_FLAGS_BASE + 1),
 		ARRAY_FLAG_USE_8_BONE_WEIGHTS = 1 << (ARRAY_COMPRESS_FLAGS_BASE + 2),
+
+		ARRAY_FLAG_USES_EMPTY_VERTEX_ARRAY = 1 << (ARRAY_INDEX + 1 + 15),
 	};
 
 	enum PrimitiveType {