PDT: Fix Library path issue, Add Trig Waves Functions

An issue occurred if you opened Blender with a new file where the
Parts Library path pointed relative to the Blender App, not the working
directory, so was not found.

The Parts Library file is now moved to the Parts Library Menu, so must
be set for new .blend files. Existing .blend files are not affected by
this change.

Error message altered to reflect the option of having this Parts Library
live anywhere.

New Feature: Add Trig Waves Functions

Requires the user to select an existing object in the Trig menu.

6 files changed, 313 insertions, 64 deletions

diff --git a/precision_drawing_tools/__init__.py b/precision_drawing_tools/__init__.py
index c2fbf647..62de72b6 100644
--- a/precision_drawing_tools/__init__.py
+++ b/precision_drawing_tools/__init__.py
@@ -29,8 +29,8 @@
 bl_info = {
     "name": "Precision Drawing Tools (PDT)",
     "author": "Alan Odom (Clockmender), Rune Morling (ermo)",
-    "version": (1, 3, 0),
-    "blender": (2, 82, 0),
+    "version": (1, 4, 0),
+    "blender": (2, 83, 0),
     "location": "View3D > UI > PDT",
     "description": "Precision Drawing Tools for Acccurate Modelling",
     "warning": "",
@@ -54,6 +54,7 @@ if "bpy" in locals():
     importlib.reload(pdt_bix)
     importlib.reload(pdt_etof)
     importlib.reload(pdt_tangent)
+    importlib.reload(pdt_trig_waves)
 else:
     from . import pdt_design
     from . import pdt_pivot_point
@@ -64,11 +65,17 @@ else:
     from . import pdt_bix
     from . import pdt_etof
     from . import pdt_tangent
+    from . import pdt_trig_waves
 
 import bpy
 import os
 from pathlib import Path
-from bpy.types import AddonPreferences, PropertyGroup, Scene, WindowManager
+from bpy.types import (
+    AddonPreferences,
+    PropertyGroup, Scene,
+    WindowManager,
+    Object,
+)
 from bpy.props import (
     BoolProperty,
     CollectionProperty,
@@ -130,6 +137,39 @@ _pdt_col_items = []
 _pdt_mat_items = []
 
 
+class PDTPreferences(AddonPreferences):
+    # This must match the addon name, use '__package__'
+    # when defining this in a submodule of a python package.
+
+    bl_idname = __name__
+
+    debug: BoolProperty(
+        name="Enable console debug output from PDT scripts",
+        default=False,
+        description="NOTE: Does not enable debugging globally in Blender (only in PDT scripts)",
+    )
+
+    pdt_ui_width: IntProperty(
+        name="UI Width Cut-off",
+        default=350,
+        description="Cutoff width for shrinking items per line in menus",
+    )
+
+    pdt_input_round: IntProperty(
+        name="Input Rounding", default=5, description="Rounding Factor for Inputs"
+    )
+
+    def draw(self, context):
+        layout = self.layout
+
+        box = layout.box()
+        row1 = box.row()
+        row2 = box.row()
+        row1.prop(self, "debug")
+        row2.prop(self, "pdt_ui_width")
+        row2.prop(self, "pdt_input_round")
+
+
 def enumlist_objects(self, context):
     """Populate Objects List from Parts Library.
 
@@ -145,8 +185,8 @@ def enumlist_objects(self, context):
 
     scene = context.scene
     pg = scene.pdt_pg
-    file_path = context.preferences.addons[__package__].preferences.pdt_library_path
-    path = Path(file_path)
+    file_path = pg.pdt_library_path
+    path = Path(bpy.path.abspath(file_path))
     _pdt_obj_items.clear()
 
     if path.is_file() and ".blend" in str(path):
@@ -158,7 +198,7 @@ def enumlist_objects(self, context):
         for object_name in object_names:
             _pdt_obj_items.append((object_name, object_name, ""))
     else:
-        _pdt_obj_items.append(("MISSING", "Library is Missing", ""))
+        _pdt_obj_items.append(("MISSING", "Library Not Set", ""))
     return _pdt_obj_items
 
 
@@ -177,8 +217,8 @@ def enumlist_collections(self, context):
 
     scene = context.scene
     pg = scene.pdt_pg
-    file_path = context.preferences.addons[__package__].preferences.pdt_library_path
-    path = Path(file_path)
+    file_path = pg.pdt_library_path
+    path = Path(bpy.path.abspath(file_path))
     _pdt_col_items.clear()
 
     if path.is_file() and ".blend" in str(path):
@@ -192,7 +232,7 @@ def enumlist_collections(self, context):
         for object_name in object_names:
             _pdt_col_items.append((object_name, object_name, ""))
     else:
-        _pdt_col_items.append(("MISSING", "Library is Missing", ""))
+        _pdt_col_items.append(("MISSING", "Library Not Set", ""))
     return _pdt_col_items
 
 
@@ -211,8 +251,8 @@ def enumlist_materials(self, context):
 
     scene = context.scene
     pg = scene.pdt_pg
-    file_path = context.preferences.addons[__package__].preferences.pdt_library_path
-    path = Path(file_path)
+    file_path = pg.pdt_library_path
+    path = Path(bpy.path.abspath(file_path))
     _pdt_mat_items.clear()
 
     if path.is_file() and ".blend" in str(path):
@@ -226,13 +266,21 @@ def enumlist_materials(self, context):
         for object_name in object_names:
             _pdt_mat_items.append((object_name, object_name, ""))
     else:
-        _pdt_mat_items.append(("MISSING", "Library is Missing", ""))
+        _pdt_mat_items.append(("MISSING", "Library Not Set", ""))
     return _pdt_mat_items
 
 
 class PDTSceneProperties(PropertyGroup):
     """Contains all PDT related properties."""
 
+    pdt_library_path: StringProperty(
+        name="Library",
+        default="",
+        description="Parts Library File",
+        maxlen=1024,
+        subtype="FILE_PATH",
+    )
+
     object_search_string: StringProperty(name="Search", default="", description=PDT_DES_LIBSER)
     collection_search_string: StringProperty(name="Search", default="", description=PDT_DES_LIBSER)
     material_search_string: StringProperty(name="Search", default="", description=PDT_DES_LIBSER)
@@ -429,48 +477,34 @@ class PDTSceneProperties(PropertyGroup):
         description=PDT_DES_TANMODE,
     )
 
-
-class PDTPreferences(AddonPreferences):
-    # This must match the addon name, use '__package__'
-    # when defining this in a submodule of a python package.
-
-    bl_idname = __name__
-
-    pdt_library_path: StringProperty(
-        name="Parts Library",
-        default="",
-        description="Parts Library File",
-        maxlen=1024,
-        subtype="FILE_PATH",
-    )
-
-    debug: BoolProperty(
-        name="Enable console debug output from PDT scripts",
-        default=False,
-        description="NOTE: Does not enable debugging globally in Blender (only in PDT scripts)",
-    )
-
-    pdt_ui_width: IntProperty(
-        name="UI Width Cut-off",
-        default=350,
-        description="Cutoff width for shrinking items per line in menus",
-    )
-
-    pdt_input_round: IntProperty(
-        name="Input Rounding", default=5, description="Rounding Factor for Inputs"
-    )
-
-    def draw(self, context):
-        layout = self.layout
-
-        box = layout.box()
-        row1 = box.row()
-        row2 = box.row()
-        row3 = box.row()
-        row1.prop(self, "debug")
-        row2.prop(self, "pdt_ui_width")
-        row2.prop(self, "pdt_input_round")
-        row3.prop(self, "pdt_library_path")
+    # For Trig Waves
+    trig_type : EnumProperty(
+        items=(
+            ("sin", "Sine", "Sine Wave"),
+            ("cos", "Cosine", "Cosine Wave"),
+            ("tan", "Tangent", "Tangent Wave"),
+        ),
+        name="Wave Form",
+        default="sin",
+        description="Trig. Wave Form",
+    )
+    trig_cycles : IntProperty(name="Cycles #", default=1, min=1,
+        description="1 Cycle = 180 Degrees")
+    trig_amp : FloatProperty(name="Amplitude", default=1, min=0.01,
+        description="Maximum Height of 1 Cycle (forms Basis for Tangents)")
+    trig_len : FloatProperty(name="Cycle Length", default=2, min=0.02,
+        description="Length in Blender Units of 1 Cycle")
+    trig_obj : PointerProperty(name="Object", type=Object)
+    trig_del : BoolProperty(name="Empty Object", default=False,
+        description="Delete ALL Vertices in Object First")
+    trig_res : IntProperty(name="Resolution", default=18, min=4, max=72,
+        description="Number of Vertices per Cycle (180 Degrees)")
+    trig_tanmax : FloatProperty(name="Tangent Max", default=10, min=0.1,
+        description="Maximum Permitted Tangent Value")
+    trig_off : FloatVectorProperty(name="Start Loc", default=(0,0,0),
+        description="Location in World Space for Origin of Wave")
+    trig_abs : BoolProperty(name="Absolute", default=False,
+        description="Use Absolute Values Only")
 
 
 # List of All Classes in the Add-on to register
@@ -479,8 +513,8 @@ class PDTPreferences(AddonPreferences):
 # (and unloaded last)
 #
 classes = (
-    PDTSceneProperties,
     PDTPreferences,
+    PDTSceneProperties,
     pdt_bix.PDT_OT_LineOnBisection,
     pdt_command.PDT_OT_CommandReRun,
     pdt_design.PDT_OT_PlacementAbs,
@@ -507,6 +541,7 @@ classes = (
     pdt_menus.PDT_PT_PanelViewControl,
     pdt_menus.PDT_PT_PanelPivotPoint,
     pdt_menus.PDT_PT_PanelPartsLibrary,
+    pdt_menus.PDT_PT_PanelTrig,
     pdt_pivot_point.PDT_OT_ModalDrawOperator,
     pdt_pivot_point.PDT_OT_ViewPlaneRotate,
     pdt_pivot_point.PDT_OT_ViewPlaneScale,
@@ -523,6 +558,7 @@ classes = (
     pdt_tangent.PDT_OT_TangentSet3,
     pdt_tangent.PDT_OT_TangentSet4,
     pdt_tangent.PDT_OT_TangentExpandMenu,
+    pdt_trig_waves.PDT_OT_WaveGenerator,
     pdt_view.PDT_OT_ViewRot,
     pdt_view.PDT_OT_ViewRotL,
     pdt_view.PDT_OT_ViewRotR,
diff --git a/precision_drawing_tools/pdt_library.py b/precision_drawing_tools/pdt_library.py
index a0b1a6be..4850481b 100644
--- a/precision_drawing_tools/pdt_library.py
+++ b/precision_drawing_tools/pdt_library.py
@@ -48,7 +48,7 @@ class PDT_OT_LibShow(Operator):
 
         scene = context.scene
         pg = scene.pdt_pg
-        file_path = context.preferences.addons[__package__].preferences.pdt_library_path
+        file_path = pg.pdt_library_path
         pg.error = str(Path(file_path))
         debug("PDT Parts Library:")
         debug(f"{pg.error}")
@@ -89,10 +89,10 @@ class PDT_OT_Append(Operator):
                 return {"FINISHED"}
 
         obj_names = [o.name for o in context.view_layer.objects].copy()
-        file_path = context.preferences.addons[__package__].preferences.pdt_library_path
+        file_path = pg.pdt_library_path
         path = Path(file_path)
 
-        if path.is_file() and ".blend" in str(path):
+        if path.is_file() and str(path).endswith(".blend"):
             if pg.lib_mode == "OBJECTS":
                 bpy.ops.wm.append(
                     filepath=str(path),
@@ -170,9 +170,10 @@ class PDT_OT_Link(Operator):
                 self.report({"ERROR"}, error_message)
                 return {"FINISHED"}
 
-        file_path = context.preferences.addons[__package__].preferences.pdt_library_path
+        file_path = pg.pdt_library_path
         path = Path(file_path)
-        if path.is_file() and ".blend" in str(path):
+
+        if path.is_file() and str(path).endswith(".blend"):
             if pg.lib_mode == "OBJECTS":
                 bpy.ops.wm.link(
                     filepath=str(path),
diff --git a/precision_drawing_tools/pdt_menus.py b/precision_drawing_tools/pdt_menus.py
index c42d18c9..be452f01 100644
--- a/precision_drawing_tools/pdt_menus.py
+++ b/precision_drawing_tools/pdt_menus.py
@@ -306,6 +306,8 @@ class PDT_PT_PanelPartsLibrary(Panel):
         layout = self.layout
         pdt_pg = context.scene.pdt_pg
         row = layout.row()
+        row.prop(pdt_pg, "pdt_library_path")
+        row = layout.row()
         col = row.column()
         col.operator("pdt.append", text="Append")
         col = row.column()
@@ -339,7 +341,7 @@ class PDT_PT_PanelPartsLibrary(Panel):
         row = box.row()
         row.prop(pdt_pg, "lib_materials", text="")
         row = box.row()
-        row.operator("pdt.lib_show", text="Show Library File", icon='INFO')
+        #row.operator("pdt.lib_show", text="Load Library File", icon='INFO')
 
 
 class PDT_PT_PanelViewControl(Panel):
@@ -474,3 +476,40 @@ class PDT_PT_PanelTangent(Panel):
             split.prop(pdt_pg, "tangent_radius1", text="")
             row = box.row()
             row.operator("pdt.tangentoperate", text="Tangents From Inputs", icon="NONE")
+
+class PDT_PT_PanelTrig(Panel):
+    bl_idname = "PDT_PT_PanelTrig"
+    bl_label = "PDT Trigonometrical Waves"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "UI"
+    bl_category = "PDT"
+    bl_options = {'DEFAULT_CLOSED'}
+
+    def draw(self,context):
+        layout = self.layout
+        pdt_pg = context.scene.pdt_pg
+        row = layout.row()
+        row.label(text=f"Working {PDT_LAB_PLANE}:")
+        row.prop(pdt_pg, "plane", text="")
+
+        row = layout.row()
+        split = row.split(factor=0.5, align=True)
+        split.prop(pdt_pg, "trig_type")
+        split.prop(pdt_pg, "trig_cycles")
+        row = layout.row()
+        split = row.split(factor=0.5, align=True)
+        split.prop(pdt_pg, "trig_amp")
+        split.prop(pdt_pg, "trig_len")
+        row = layout.row()
+        split = row.split(factor=0.5, align=True)
+        split.prop(pdt_pg, "trig_obj", text="")
+        split.prop(pdt_pg, "trig_del")
+        row = layout.row()
+        split = row.split(factor=0.5, align=True)
+        split.prop(pdt_pg, "trig_res")
+        split.prop(pdt_pg, "trig_tanmax")
+        row = layout.row()
+        row.prop(pdt_pg, "trig_off")
+        row = layout.row()
+        row.operator("pdt.wave_generator", icon="SEQ_LUMA_WAVEFORM")
+        row.prop(pdt_pg, "trig_abs")
diff --git a/precision_drawing_tools/pdt_msg_strings.py b/precision_drawing_tools/pdt_msg_strings.py
index 8d01abb2..7d0cc2bc 100644
--- a/precision_drawing_tools/pdt_msg_strings.py
+++ b/precision_drawing_tools/pdt_msg_strings.py
@@ -94,8 +94,8 @@ PDT_ERR_VERT_MODE = "Work in Vertex Mode for this Function"
 PDT_ERR_NOPPLOC = (
     "Custom Property PDT_PP_LOC for this object not found, have you Written it yet?"
 )
-PDT_ERR_NO_LIBRARY = ("PDT Library Blend File (parts_library.blend) is Missing "
-                      + "from Addons/clockworxpdt Folder")
+PDT_ERR_NO_LIBRARY = ("PDT Library Blend File is Missing "
+                      + "or not Correctly Set to a Blend File")
 
 PDT_ERR_SEL_1_VERTI = "Select at least 1 Vertex Individually (Currently selected:"
 PDT_ERR_SEL_1_VERT = "Select at least 1 Vertex (Currently selected:"
diff --git a/precision_drawing_tools/pdt_tangent.py b/precision_drawing_tools/pdt_tangent.py
index d743d3eb..22b34c7a 100644
--- a/precision_drawing_tools/pdt_tangent.py
+++ b/precision_drawing_tools/pdt_tangent.py
@@ -114,6 +114,8 @@ def get_tangent_points(context, hloc_0, vloc_0, radius_0, hloc_p, vloc_p):
         vloc_t2: Vertical Location of Second Tangent Point
     """
 
+    # Uses basic Pythagorus' theorem to compute locations
+    #
     numerator = (radius_0 ** 2 * (hloc_p - hloc_0)) + (
         radius_0
         * (vloc_p - vloc_0)
@@ -186,6 +188,8 @@ def make_vectors(coords, a1, a2, a3, pg):
     tangent_vector_o4[a3] = coords[8]
 
     if pg.plane == "LO":
+        # Reset coordinates from view local (Horiz, Vert, depth) to World XYZ.
+        #
         tangent_vector_o1 = view_coords(
             tangent_vector_o1[a1], tangent_vector_o1[a2], tangent_vector_o1[a3]
         )
@@ -223,6 +227,8 @@ def tangent_setup(context, pg, plane, obj_data, centre_0, centre_1, centre_2, ra
     a1, a2, a3 = set_mode(plane)
     mode = pg.tangent_mode
     if plane == "LO":
+        # Translate world cordinates into view local (horiz, vert, depth)
+        #
         centre_0 = view_coords_i(centre_0[a1], centre_0[a2], centre_0[a3])
         centre_1 = view_coords_i(centre_1[a1], centre_1[a2], centre_1[a3])
         centre_2 = view_coords_i(centre_2[a1], centre_2[a2], centre_2[a3])
@@ -239,6 +245,7 @@ def tangent_setup(context, pg, plane, obj_data, centre_0, centre_1, centre_2, ra
         (distance <= radius_0 or distance <= radius_1 and mode in {"outer", "both"})
         ):
         # Cannot execute, centres are too close.
+        #
         pg.error = f"{PDT_ERR_BADDISTANCE}"
         context.window_manager.popup_menu(oops, title="Error", icon="ERROR")
         return {"FINISHED"}
@@ -260,6 +267,7 @@ def tangent_setup(context, pg, plane, obj_data, centre_0, centre_1, centre_2, ra
             context.window_manager.popup_menu(oops, title="Error", icon="ERROR")
             return {"FINISHED"}
         # Point Tangents
+        #
         tangent_vector_o1 = Vector((0, 0, 0))
         tangent_vector_o1[a1] = hloc_to1
         tangent_vector_o1[a2] = vloc_to1
@@ -269,6 +277,8 @@ def tangent_setup(context, pg, plane, obj_data, centre_0, centre_1, centre_2, ra
         tangent_vector_o2[a2] = vloc_to2
         tangent_vector_o2[a3] = centre_2[a3]
         if pg.plane == "LO":
+            # Translate view local coordinates (horiz, vert, depth) into World XYZ
+            #
             centre_2 = view_coords(centre_2[a1], centre_2[a2], centre_2[a3])
             tangent_vector_o1 = view_coords(
                 tangent_vector_o1[a1], tangent_vector_o1[a2], tangent_vector_o1[a3]
@@ -287,8 +297,11 @@ def tangent_setup(context, pg, plane, obj_data, centre_0, centre_1, centre_2, ra
     """
 
     if mode in {"outer", "both"}:
+        # Uses basic trigonometry and Pythagorus' theorem to compute locations
+        #
         if radius_0 == radius_1:
             # No intersection point for outer tangents
+            #
             sin_angle = (centre_1[a2] - centre_0[a2]) / distance
             cos_angle = (centre_1[a1] - centre_0[a1]) / distance
             hloc_to1 = centre_0[a1] + (radius_0 * sin_angle)
@@ -342,6 +355,8 @@ def tangent_setup(context, pg, plane, obj_data, centre_0, centre_1, centre_2, ra
     """
 
     if mode in {"inner", "both"}:
+        # Uses basic trigonometry and Pythagorus' theorem to compute locations
+        #
         hloc_pi, vloc_pi = get_tangent_intersect_inner(
             centre_0[a1], centre_0[a2], centre_1[a1], centre_1[a2], radius_0, radius_1
         )
@@ -442,6 +457,8 @@ def analyse_arc(context, pg):
             context.window_manager.popup_menu(oops, title="Error", icon="ERROR")
             raise PDT_SelectionError
         vector_a = verts[0].co
+        # Get the nearest to middle vertex of the arc
+        #
         vector_b = verts[int(floor(len(verts) / 2))].co
         vector_c = verts[-1].co
         vector_delta, radius = arc_centre(vector_a, vector_b, vector_c)
@@ -484,6 +501,7 @@ class PDT_OT_TangentOperate(Operator):
         Returns:
             Nothing.
         """
+
         scene = context.scene
         pg = scene.pdt_pg
         plane = pg.plane
@@ -521,7 +539,7 @@ class PDT_OT_TangentOperateSel(Operator):
     bl_idname = "pdt.tangentoperatesel"
     bl_label = "Calculate Tangents"
     bl_options = {"REGISTER", "UNDO"}
-    bl_description = "Calculate Tangents to Arcs from 2 Selected Vertices, or 1 & Point"
+    bl_description = "Calculate Tangents to Arcs from 2 Selected Vertices, or 1 & Point in Menu"
 
     @classmethod
     def poll(cls, context):
@@ -601,6 +619,8 @@ class PDT_OT_TangentOperateSel(Operator):
             e.select_set(False)
         bmesh.update_edit_mesh(obj.data)
         bm.select_history.clear()
+        # Select the nearest to middle vertex in the arc
+        #
         verts1 = [verts1[0].co, verts1[int(floor(len(verts1) / 2))].co, verts1[-1].co]
         vertsn = [vertsn[0].co, vertsn[int(floor(len(vertsn) / 2))].co, vertsn[-1].co]
         centre_0, radius_0 = arc_centre(verts1[0], verts1[1], verts1[2])
@@ -756,6 +776,9 @@ class PDT_OT_TangentExpandMenu(Operator):
     def execute(self, context):
         """Expand/Collapse Tangent Menu.
 
+        Note:
+            This is used to add further options to the menu.
+
         Args:
             context: Blender bpy.context instance.
 
diff --git a/precision_drawing_tools/pdt_trig_waves.py b/precision_drawing_tools/pdt_trig_waves.py
new file mode 100644
index 00000000..535ac85a
--- /dev/null
+++ b/precision_drawing_tools/pdt_trig_waves.py
@@ -0,0 +1,150 @@
+# ***** BEGIN GPL LICENSE BLOCK *****
+#
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ***** END GPL LICENCE BLOCK *****
+#
+# -----------------------------------------------------------------------
+# Author: Alan Odom (Clockmender), Rune Morling (ermo) Copyright (c) 2019
+# -----------------------------------------------------------------------
+#
+import bpy
+import bmesh
+from math import sin, cos, tan, pi
+from mathutils import Vector
+from .pdt_functions import (
+    set_mode,
+    view_coords,
+)
+
+class PDT_OT_WaveGenerator(bpy.types.Operator):
+    """Generate Trig Waves in Active Object"""
+    bl_idname = "pdt.wave_generator"
+    bl_label = "Generate Waves"
+    bl_options = {"REGISTER", "UNDO"}
+
+    @classmethod
+    def poll(cls, context):
+        pg = context.scene.pdt_pg
+        return pg.trig_obj is not None
+
+    def execute(self, context):
+        """Generate Trig Waves in Active Object.
+
+        Note:
+            Uses all the PDT trig_* variables.
+
+            This function will draw a trigonometrical wave based upon cycle length
+            One cycle is assumed to be 180 degrees, so half a revolution of an imaginary
+            rotating object. If a full cycle from 0 to 360 degrees is required, the cycles
+            number should be set to 2.
+
+        Args:
+            context: Blender bpy.context instance.
+
+        Returns:
+            Nothing.
+        """
+
+        pg = context.scene.pdt_pg
+        plane = pg.plane
+        # Find the horizontal, vertical and depth axes in the view from working plane.
+        # Order is: H, V, D.
+        #
+        a1, a2, a3 = set_mode(plane)
+        # Make sure object selected in the UI is the active object.
+        #
+        for obj in bpy.data.objects:
+            obj.select_set(state=False)
+        context.view_layer.objects.active = pg.trig_obj
+        # x_inc is the increase in X (Horiz axis) per unit of resolution of the wave, so if
+        # resolution is 9, nine points will be drawn in each cycle representing increases of
+        # 20 degrees and 1/9th of the cycle length.
+        #
+        x_inc = pg.trig_len / pg.trig_res
+
+        if pg.trig_del:
+            # Delete all existing vertices first.
+            #
+            bpy.ops.object.mode_set(mode='EDIT')
+            for v in pg.trig_obj.data.vertices:
+                v.select = True
+            bpy.ops.mesh.delete(type='VERT')
+            bpy.ops.object.mode_set(mode='OBJECT')
+
+        if pg.trig_obj.mode != "EDIT":
+            bpy.ops.object.mode_set(mode='EDIT')
+        bm = bmesh.from_edit_mesh(pg.trig_obj.data)
+
+        # Loop for each point in the number of cycles times the resolution value.
+        # Uses basic trigonomtry to calculate the wave locations.
+        # If Absolute has been set, all values are made positive.
+        # z_val is assumed to be the offset from the horizontal axis of the wave.
+        # These values will be offset by the Offset Vector given in the UI.
+        #
+        for i in range((pg.trig_res * pg.trig_cycles) + 1):
+            # Uses a calculation of trig function angle of imaginary object times maximum amplitude
+            # of wave. So with reolution at 9, angular increments are 20 degrees.
+            # Angles must be in Radians for this calcultion.
+            #
+            if pg.trig_type == "sin":
+                if pg.trig_abs:
+                    z_val = abs(sin((i / pg.trig_res) * pi) * pg.trig_amp)
+                else:
+                    z_val = sin((i / pg.trig_res) * pi) * pg.trig_amp
+            elif pg.trig_type == "cos":
+                if pg.trig_abs:
+                    z_val = abs(cos((i / pg.trig_res) * pi) * pg.trig_amp)
+                else:
+                    z_val = cos((i / pg.trig_res) * pi) * pg.trig_amp
+            else:
+                if pg.trig_abs:
+                    z_val = abs(tan((i / pg.trig_res) * pi) * pg.trig_amp)
+                else:
+                    z_val = tan((i / pg.trig_res) * pi) * pg.trig_amp
+
+                if abs(z_val) > pg.trig_tanmax:
+                    if z_val >= 0:
+                        z_val = pg.trig_tanmax
+                    else:
+                        if pg.trig_abs:
+                            z_val = pg.trig_tanmax
+                        else:
+                            z_val = -pg.trig_tanmax
+
+            # Start with Offset Vector from UI and add wave offsets to it.
+            # Axis a3 (depth) is never changed from offset vector in UI.
+            #
+            vert_loc = Vector(pg.trig_off)
+            vert_loc[a1] = vert_loc[a1] + (i * x_inc)
+            vert_loc[a2] = vert_loc[a2] + z_val
+            if plane == "LO":
+                # Translate view local coordinates (horiz, vert, depth) into World XYZ
+                #
+                vert_loc = view_coords(vert_loc[a1], vert_loc[a2], vert_loc[a3])
+            vertex_new = bm.verts.new(vert_loc)
+            # Refresh Vertices list in object data.
+            #
+            bm.verts.ensure_lookup_table()
+            if i > 0:
+                # Make an edge from last two vertices in object data.
+                #
+                bm.edges.new([bm.verts[-2], vertex_new])
+
+        bmesh.update_edit_mesh(pg.trig_obj.data)
+        bpy.ops.object.mode_set(mode='OBJECT')
+
+        return {"FINISHED"}