Disable VRAM compression by default for small textures in Detect 3D

This is done to prevent reducing texture quality when it doesn't save
much video memory, especially for pixel art.

The size threshold can be adjusted in the project settings.
To get the previous behavior where textures detected to be used in 3D
had their compression mode always set to VRAM, set this to the lowest value
(16).

core/config/project_settings.cpp

@@ -1246,6 +1246,9 @@ ProjectSettings::ProjectSettings() {
 	GLOBAL_DEF_INTERNAL("application/config/features", PackedStringArray());
 	GLOBAL_DEF_INTERNAL("internationalization/locale/translation_remaps", PackedStringArray());
 	GLOBAL_DEF_INTERNAL("internationalization/locale/translations", PackedStringArray());
+
+	GLOBAL_DEF("rendering/textures/vram_compression/minimum_size", 512);
+	custom_prop_info["rendering/textures/vram_compression/minimum_size"] = PropertyInfo(Variant::INT, "rendering/textures/vram_compression/minimum_size", PROPERTY_HINT_RANGE, "16,16384,1");
 }
 
 ProjectSettings::~ProjectSettings() {

doc/classes/ProjectSettings.xml

@@ -1924,6 +1924,11 @@
 			If [code]true[/code], the texture importer will import VRAM-compressed textures using the S3 Texture Compression algorithm. This algorithm is only supported on desktop platforms and consoles.
 			[b]Note:[/b] Changing this setting does [i]not[/i] impact textures that were already imported before. To make this setting apply to textures that were already imported, exit the editor, remove the [code].godot/imported/[/code] folder located inside the project folder then restart the editor (see [member application/config/use_hidden_project_data_directory]).
 		</member>
+		<member name="rendering/textures/vram_compression/minimum_size" type="int" setter="" getter="" default="512">
+			When a texture is detected as used in 3D in the editor, only enable VRAM compression if its size is greater than or equal to [code]minimum_size * minimum_size[/code] pixels. This is done to prevent reducing texture quality when it doesn't save much video memory, especially for pixel art.
+			For non-square textures, the pixel count is used. For example, with [member rendering/textures/vram_compression/minimum_size] set to [code]512[/code], a 512×512 texture will use VRAM compression, while 256×256 textures, 256×512 and 1024×64 textures will keep their existing compression mode (Lossless by default).
+			[b]Note:[/b] This project setting only affects textures that are detected to be used in 3D at a given time. Textures that were already imported will not be affected by changes to this setting. To force 3D detection to occur again, select a texture in the FileSystem dock, change its Detect 3D import option in the Import dock to [b]VRAM Compressed[/b] or [b]Basis Universal[/b] then click [b]Reimport[/b].
+		</member>
 		<member name="rendering/vulkan/descriptor_pools/max_descriptors_per_pool" type="int" setter="" getter="" default="64">
 		</member>
 		<member name="rendering/vulkan/rendering/back_end" type="int" setter="" getter="" default="0">

editor/import/resource_importer_texture.cpp

@@ -65,6 +65,15 @@ void ResourceImporterTexture::_texture_reimport_3d(const Ref<CompressedTexture2D
 	}
 
 	singleton->make_flags[path].flags |= MAKE_3D_FLAG;
+
+	// For small textures, don't use VRAM compression as it decreases quality too much compared to the memory saved.
+	// The minimum size for VRAM compression is defined on each axis.
+	// It is then squared to handle non-square input texture sizes in a more human-readable manner.
+	const float minimum_size = float(GLOBAL_GET("rendering/textures/vram_compression/minimum_size"));
+	if (p_tex->get_width() * p_tex->get_height() >= int(Math::pow(minimum_size, 2.0f) - CMP_EPSILON)) {
+		// Texture is larger than `minimum_size × minimum_size` pixels (if square).
+		singleton->make_flags[path].flags |= MAKE_VRAM_COMPRESS_FLAG;
+	}
 }
 
 void ResourceImporterTexture::_texture_reimport_normal(const Ref<CompressedTexture2D> &p_tex) {
@@ -103,7 +112,33 @@ void ResourceImporterTexture::update_imports() {
 
 			bool changed = false;
 
-			if (E.value.flags & MAKE_NORMAL_FLAG && int(cf->get_value("params", "compress/normal_map")) == 0) {
+			if (E.value.flags & MAKE_3D_FLAG && bool(cf->get_value("params", "detect_3d/compress_to"))) {
+				if (E.value.flags & MAKE_VRAM_COMPRESS_FLAG) {
+					// Texture is large enough to benefit from VRAM compression.
+					const int compress_to = cf->get_value("params", "detect_3d/compress_to");
+					String compress_string;
+					if (compress_to == 1) {
+						cf->set_value("params", "compress/mode", COMPRESS_VRAM_COMPRESSED);
+						compress_string = "VRAM Compressed (S3TC/ETC/BPTC)";
+					} else if (compress_to == 2) {
+						cf->set_value("params", "compress/mode", COMPRESS_BASIS_UNIVERSAL);
+						compress_string = "Basis Universal";
+					}
+					print_line(vformat(TTR("%s: Texture detected as used in 3D. Enabling mipmap generation and setting the texture compression mode to %s."), String(E.key), compress_string));
+				} else {
+					print_line(vformat(TTR("%s: Small texture detected as used in 3D. Enabling mipmap generation but not VRAM compression."), String(E.key)));
+				}
+
+				cf->set_value("params", "mipmaps/generate", true);
+				cf->set_value("params", "detect_3d/compress_to", 0);
+
+				changed = true;
+			}
+
+			if (E.value.flags & MAKE_NORMAL_FLAG && int(cf->get_value("params", "compress/normal_map")) == 0 && int(cf->get_value("params", "compress/mode")) != COMPRESS_LOSSLESS) {
+				// Normal map compression is not available for textures with Lossless compression.
+				// This is ignored in the importer, but printing a message about normal map compression
+				// being enabled in this case is misleading.
 				print_line(vformat(TTR("%s: Texture detected as used as a normal map in 3D. Enabling red-green texture compression to reduce memory usage (blue channel is discarded)."), String(E.key)));
 				cf->set_value("params", "compress/normal_map", 1);
 				changed = true;
@@ -116,22 +151,6 @@ void ResourceImporterTexture::update_imports() {
 				changed = true;
 			}
 
-			if (E.value.flags & MAKE_3D_FLAG && bool(cf->get_value("params", "detect_3d/compress_to"))) {
-				const int compress_to = cf->get_value("params", "detect_3d/compress_to");
-				String compress_string;
-				cf->set_value("params", "detect_3d/compress_to", 0);
-				if (compress_to == 1) {
-					cf->set_value("params", "compress/mode", COMPRESS_VRAM_COMPRESSED);
-					compress_string = "VRAM Compressed (S3TC/ETC/BPTC)";
-				} else if (compress_to == 2) {
-					cf->set_value("params", "compress/mode", COMPRESS_BASIS_UNIVERSAL);
-					compress_string = "Basis Universal";
-				}
-				print_line(vformat(TTR("%s: Texture detected as used in 3D. Enabling mipmap generation and setting the texture compression mode to %s."), String(E.key), compress_string));
-				cf->set_value("params", "mipmaps/generate", true);
-				changed = true;
-			}
-
 			if (changed) {
 				cf->save(src_path);
 				to_reimport.push_back(E.key);

editor/import/resource_importer_texture.h

@@ -54,8 +54,9 @@ public:
 protected:
 	enum {
 		MAKE_3D_FLAG = 1,
-		MAKE_ROUGHNESS_FLAG = 2,
+		MAKE_VRAM_COMPRESS_FLAG = 2,
-		MAKE_NORMAL_FLAG = 4
+		MAKE_ROUGHNESS_FLAG = 4,
+		MAKE_NORMAL_FLAG = 8,
 	};
 
 	Mutex mutex;