From ab930a71ca076480f78a6a5f42ac2ff5cef24d08 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sun, 22 Sep 2019 15:56:40 +0200
Subject: Enable mouse-based view rotation

---
 channel_3d_volumetric_rendering_gl_interop.py | 18 ++++--------------
 utility/mouse.py                              | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+), 14 deletions(-)
 create mode 100644 utility/mouse.py

diff --git a/channel_3d_volumetric_rendering_gl_interop.py b/channel_3d_volumetric_rendering_gl_interop.py
index 9e9555a..d3fe485 100644
--- a/channel_3d_volumetric_rendering_gl_interop.py
+++ b/channel_3d_volumetric_rendering_gl_interop.py
@@ -19,6 +19,7 @@ from geometry.box      import Box
 from geometry.cylinder import Cylinder
 
 from utility.opengl import MomentsTexture
+from utility.mouse  import MouseDragMonitor
 
 lattice_x = 256
 lattice_y = 64
@@ -286,19 +287,7 @@ def on_reshape(width, height):
     glViewport(0,0,width,height)
     projection = get_projection(width, height)
 
-def on_keyboard(key, *args):
-    global rotation
-
-    x = {
-        b'w': -numpy.pi/20,
-        b's':  numpy.pi/20
-    }.get(key, 0.0)
-    z = {
-        b'a':  numpy.pi/20,
-        b'd': -numpy.pi/20
-    }.get(key, 0.0)
-
-    rotation.update(x,z)
+mouse_monitor = MouseDragMonitor(GLUT_LEFT_BUTTON, lambda dx, dy: rotation.update(0.005*dy, 0.005*dx))
 
 def on_timer(t):
     glutTimerFunc(t, on_timer, t)
@@ -306,7 +295,8 @@ def on_timer(t):
 
 glutDisplayFunc(on_display)
 glutReshapeFunc(on_reshape)
-glutKeyboardFunc(on_keyboard)
+glutMouseFunc(mouse_monitor.on_mouse)
+glutMotionFunc(mouse_monitor.on_mouse_move)
 glutTimerFunc(10, on_timer, 10)
 
 glutMainLoop()
diff --git a/utility/mouse.py b/utility/mouse.py
new file mode 100644
index 0000000..c36d7e8
--- /dev/null
+++ b/utility/mouse.py
@@ -0,0 +1,21 @@
+from OpenGL.GLUT import *
+
+class MouseDragMonitor:
+    def __init__(self, button, callback):
+        self.button   = button
+        self.callback = callback
+        self.active   = False
+
+    def on_mouse(self, button, state, x, y):
+        if button == self.button:
+            self.active = (state == GLUT_DOWN)
+            self.last_x = x
+            self.last_y = y
+
+    def on_mouse_move(self, x, y):
+        if self.active:
+            delta_x = self.last_x - x
+            delta_y = y - self.last_y
+            self.last_x = x
+            self.last_y = y
+            self.callback(delta_x, delta_y)
-- 
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