1 files changed, 110 insertions, 0 deletions
diff --git a/sun_position/north.py b/sun_position/north.py
new file mode 100644
index 00000000..44b4ee09
--- /dev/null
+++ b/sun_position/north.py
@@ -0,0 +1,110 @@
+### 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 LICENSE BLOCK #####
+
+import bpy
+import bgl
+import math
+import gpu
+from gpu_extras.batch import batch_for_shader
+from mathutils import Vector
+
+
+if bpy.app.background:  # ignore north line in background mode
+    def north_update(self, context):
+        pass
+else:
+    vertex_shader = '''
+        uniform mat4 u_ViewProjectionMatrix;
+
+        in vec3 position;
+
+        flat out vec2 v_StartPos;
+        out vec4 v_VertPos;
+
+        void main()
+        {
+            vec4 pos    = u_ViewProjectionMatrix * vec4(position, 1.0f);
+            gl_Position = pos;
+            v_StartPos    = (pos / pos.w).xy;
+            v_VertPos     = pos;
+        }
+    '''
+
+    fragment_shader = '''
+        uniform vec4 u_Color;
+
+        flat in vec2 v_StartPos;
+        in vec4 v_VertPos;
+
+        uniform vec2 u_Resolution;
+
+        void main()
+        {
+            vec4 vertPos_2d = v_VertPos / v_VertPos.w;
+            vec2 dir  = (vertPos_2d.xy - v_StartPos.xy) * u_Resolution;
+            float dist = length(dir);
+
+            if (step(sin(dist / 5.0f), 0.0) == 1) discard;
+
+            gl_FragColor = u_Color;
+        }
+    '''
+
+    shader = gpu.types.GPUShader(vertex_shader, fragment_shader)
+
+    def draw_north_callback():
+        # ------------------------------------------------------------------
+        # Set up the compass needle using the current north offset angle
+        # less 90 degrees.  This forces the unit circle to begin at the
+        # 12 O'clock instead of 3 O'clock position.
+        # ------------------------------------------------------------------
+        sun_props = bpy.context.scene.sun_pos_properties
+
+        color = (0.2, 0.6, 1.0, 0.7)
+        radius = 100
+        angle = -(sun_props.north_offset - math.pi / 2)
+        x = math.cos(angle) * radius
+        y = math.sin(angle) * radius
+
+        coords = Vector((x, y, 0)), Vector((0, 0, 0))   # Start & end of needle
+
+        batch = batch_for_shader(
+            shader, 'LINE_STRIP',
+            {"position": coords},
+        )
+        shader.bind()
+
+        matrix = bpy.context.region_data.perspective_matrix
+        shader.uniform_float("u_ViewProjectionMatrix", matrix)
+        shader.uniform_float("u_Resolution", (bpy.context.region.width, bpy.context.region.height))
+        shader.uniform_float("u_Color", color)
+        bgl.glLineWidth(2.0)
+        batch.draw(shader)
+
+
+    _handle = None
+
+
+    def north_update(self, context):
+        global _handle
+        if self.show_north and _handle is None:
+            _handle = bpy.types.SpaceView3D.draw_handler_add(draw_north_callback, (), 'WINDOW', 'POST_VIEW')
+        elif _handle is not None:
+            bpy.types.SpaceView3D.draw_handler_remove(_handle, 'WINDOW')
+            _handle = None
+        context.area.tag_redraw()