Add render mode to ensure correct normals when using non-uniform scaling

drivers/gles3/shader_compiler_gles3.cpp

@@ -898,6 +898,7 @@ ShaderCompilerGLES3::ShaderCompilerGLES3() {
 
 	actions[VS::SHADER_SPATIAL].render_mode_defines["skip_vertex_transform"] = "#define SKIP_TRANSFORM_USED\n";
 	actions[VS::SHADER_SPATIAL].render_mode_defines["world_vertex_coords"] = "#define VERTEX_WORLD_COORDS_USED\n";
+	actions[VS::SHADER_SPATIAL].render_mode_defines["ensure_correct_normals"] = "#define ENSURE_CORRECT_NORMALS\n";
 	actions[VS::SHADER_SPATIAL].render_mode_defines["cull_front"] = "#define DO_SIDE_CHECK\n";
 	actions[VS::SHADER_SPATIAL].render_mode_defines["cull_disabled"] = "#define DO_SIDE_CHECK\n";
 

drivers/gles3/shaders/scene.glsl

@@ -322,7 +322,13 @@ void main() {
 #if !defined(SKIP_TRANSFORM_USED) && defined(VERTEX_WORLD_COORDS_USED)
 
 	vertex = world_matrix * vertex;
+
+#if defined(ENSURE_CORRECT_NORMALS)
+	mat3 normal_matrix = mat3(transpose(inverse(world_matrix)));
+	normal = normal_matrix * normal;
+#else
 	normal = normalize((world_matrix * vec4(normal,0.0)).xyz);
+#endif
 
 #if defined(ENABLE_TANGENT_INTERP) || defined(ENABLE_NORMALMAP) || defined(LIGHT_USE_ANISOTROPY)
 
@@ -394,7 +400,13 @@ VERTEX_SHADER_CODE
 #if !defined(SKIP_TRANSFORM_USED) && !defined(VERTEX_WORLD_COORDS_USED)
 
 	vertex = modelview * vertex;
+
+#if defined(ENSURE_CORRECT_NORMALS)
+	mat3 normal_matrix = mat3(transpose(inverse(modelview)));
+	normal = normal_matrix * normal;
+#else
 	normal = normalize((modelview * vec4(normal,0.0)).xyz);
+#endif
 
 #if defined(ENABLE_TANGENT_INTERP) || defined(ENABLE_NORMALMAP) || defined(LIGHT_USE_ANISOTROPY)
 

scene/resources/material.cpp

@@ -393,6 +393,9 @@ void SpatialMaterial::_update_shader() {
 	if (flags[FLAG_DONT_RECEIVE_SHADOWS]) {
 		code += ",shadows_disabled";
 	}
+	if (flags[FLAG_ENSURE_CORRECT_NORMALS]) {
+		code += ",ensure_correct_normals";
+	}
 	code += ";\n";
 
 	code += "uniform vec4 albedo : hint_color;\n";
@@ -1852,6 +1855,7 @@ void SpatialMaterial::_bind_methods() {
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "flags_fixed_size"), "set_flag", "get_flag", FLAG_FIXED_SIZE);
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "flags_albedo_tex_force_srgb"), "set_flag", "get_flag", FLAG_ALBEDO_TEXTURE_FORCE_SRGB);
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "flags_do_not_receive_shadows"), "set_flag", "get_flag", FLAG_DONT_RECEIVE_SHADOWS);
+	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "flags_ensure_correct_normals"), "set_flag", "get_flag", FLAG_ENSURE_CORRECT_NORMALS);
 	ADD_GROUP("Vertex Color", "vertex_color");
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "vertex_color_use_as_albedo"), "set_flag", "get_flag", FLAG_ALBEDO_FROM_VERTEX_COLOR);
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "vertex_color_is_srgb"), "set_flag", "get_flag", FLAG_SRGB_VERTEX_COLOR);
@@ -2042,6 +2046,7 @@ void SpatialMaterial::_bind_methods() {
 	BIND_ENUM_CONSTANT(FLAG_TRIPLANAR_USE_WORLD);
 	BIND_ENUM_CONSTANT(FLAG_ALBEDO_TEXTURE_FORCE_SRGB);
 	BIND_ENUM_CONSTANT(FLAG_DONT_RECEIVE_SHADOWS);
+	BIND_ENUM_CONSTANT(FLAG_ENSURE_CORRECT_NORMALS);
 	BIND_ENUM_CONSTANT(FLAG_MAX);
 
 	BIND_ENUM_CONSTANT(DIFFUSE_BURLEY);

scene/resources/material.h

@@ -189,6 +189,7 @@ public:
 		FLAG_USE_ALPHA_SCISSOR,
 		FLAG_ALBEDO_TEXTURE_FORCE_SRGB,
 		FLAG_DONT_RECEIVE_SHADOWS,
+		FLAG_ENSURE_CORRECT_NORMALS,
 		FLAG_MAX
 	};
 
@@ -237,7 +238,7 @@ private:
 			uint64_t blend_mode : 2;
 			uint64_t depth_draw_mode : 2;
 			uint64_t cull_mode : 2;
-			uint64_t flags : 15;
+			uint64_t flags : 16;
 			uint64_t detail_blend_mode : 2;
 			uint64_t diffuse_mode : 3;
 			uint64_t specular_mode : 2;

servers/visual/shader_types.cpp

@@ -172,6 +172,7 @@ ShaderTypes::ShaderTypes() {
 
 	shader_modes[VS::SHADER_SPATIAL].modes.insert("skip_vertex_transform");
 	shader_modes[VS::SHADER_SPATIAL].modes.insert("world_vertex_coords");
+	shader_modes[VS::SHADER_SPATIAL].modes.insert("ensure_correct_normals");
 
 	shader_modes[VS::SHADER_SPATIAL].modes.insert("shadows_disabled");