Add multiple surface functionality for meshes in Footstep System

COGITO/DynamicFootstepSystem/Scripts/footstep_surface_detector.gd

@@ -4,6 +4,7 @@ class_name FootstepSurfaceDetector
 
 @export var generic_fallback_footstep_profile : AudioStreamRandomizer
 @export var footstep_material_library : FootstepMaterialLibrary
+var last_result
 
 func _ready():
 	if not generic_fallback_footstep_profile:
@@ -14,6 +15,7 @@ func play_footstep():
 	var result = get_world_3d().direct_space_state.intersect_ray(query)
 	if result:
 
+		last_result = result
 		if _play_by_footstep_surface(result.collider):
 			return
 		elif _play_by_material(result.collider):
@@ -59,14 +61,82 @@ func _get_footstep_surface_child(collider : Node3D) -> AudioStreamRandomizer:
 	return null
 
 func _get_surface_material(collider : Node3D) -> Material:
+	var mesh_instance = null
+	var meshes = []
 	if collider is CSGShape3D:
-		return collider.material
+		if collider is CSGCombiner3D:
+			#composite mesh
+			if collider.material_override:
+				return collider.material_override
+			meshes = collider.get_meshes()
+		else:
+			return collider.material
 	elif collider is StaticBody3D or collider is RigidBody3D:
 		#find all children of the collider static body that are of type "MeshInstance3D"
 		#if there are multiple materials, just default to the first one found
-		var mesh_instances = collider.find_children("", "MeshInstance3D")
-		if mesh_instances:
-			return mesh_instances[0].mesh.material
+		if collider.get_parent() is MeshInstance3D:
+			mesh_instance = collider.get_parent()
+		else:
+			var mesh_instances = collider.find_children("", "MeshInstance3D")
+			if mesh_instances:
+				if len(mesh_instances) == 1:
+					mesh_instance = mesh_instances[0]
+				else:
+					meshes = mesh_instances
+
+	if meshes:
+		#TODO: Handle multiple meshes
+		mesh_instance = meshes[0]
+
+	if mesh_instance and 'mesh' in mesh_instance:
+		var mesh = mesh_instance.mesh
+		if mesh.get_surface_count() == 0:
+			return null
+		elif mesh.get_surface_count() == 1:
+			return mesh.surface_get_material(0)
+		else:
+			var face = null
+
+			var ray = last_result['position'] - global_position
+			var faces = mesh.get_faces()
+
+			var aabb = mesh.get_aabb() as AABB
+			var accuracy = round(4*aabb.size.length_squared()) # dynamically calculate a reasonable grid size
+			var snap = aabb.size/accuracy # this will be the size of our units to snap to
+
+			var coord = null
+
+			for i in range(len(faces) / 3):
+				# first, figure out what face we're standing on
+				var face_idx = i * 3
+				var a = mesh_instance.to_global(faces[face_idx])
+				var b = mesh_instance.to_global(faces[face_idx+1])
+				var c = mesh_instance.to_global(faces[face_idx+2])
+				var ray_t = Geometry3D.ray_intersects_triangle(global_position,ray,a,b,c)
+				if ray_t:
+					face = faces.slice(face_idx,face_idx+3)
+					# round out vert coordinates to avoid floating point errors
+					coord = [round(faces[face_idx]/snap),round(faces[face_idx+1]/snap),round(faces[face_idx+2]/snap)]
+					break
+			var mat = null
+			if face:
+				for surface in range(mesh.get_surface_count()):
+					var surf = mesh.surface_get_arrays(surface)[0]
+					var has_vert_a = false
+					var has_vert_b = false
+					var has_vert_c = false
+					for vert in surf:
+						var vert_coord = round(vert/snap)
+						has_vert_a = has_vert_a or vert_coord == coord[0]
+						has_vert_b = has_vert_b or vert_coord == coord[1]
+						has_vert_c = has_vert_c or vert_coord == coord[2]
+						if has_vert_a and has_vert_b and has_vert_c:
+							# we found it! note the material and break free!
+							mat = mesh.surface_get_material(surface)
+							break
+					if has_vert_a and has_vert_b and has_vert_c:
+						break
+			return mat
 	return null
 
 func _play_footstep(footstep_profile : AudioStreamRandomizer):