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--- kurse:efcomputergrafik:teil2:brainstorm [2019/11/17 14:10]
Ivo Blöchliger [Manipulation in Python]
+++ kurse:efcomputergrafik:teil2:brainstorm [2019/11/19 09:52]
Ivo Blöchliger
@@ Line 1: / Line 1: @@
+====== Intro ======
+  * meine Wenigkeit
+  * Warum Bezier-Kurven?
 ====== Ziele ======
   * Physikalisch halbwegs realistische Achterbahn mit Blender
@@ Line 4: / Line 8: @@
 ====== Programm ======
+  * Software auf Schulcomputern: https://fginfo.ksbg.ch/dokuwiki/doku.php?id=lehrkraefte:blc:informatik:glf19:glf19#make_the_computer_zimmer_great_again
   * Demo mit Inkscape (https://inkscape.org/release/0.92.4/windows/64-bit/)
   * Geometrische Definition
@@ Line 42: / Line 47: @@
+==== Auslesen der Daten ====
+<code python>
+import bpy
+obj = bpy.data.objects['BezierCurve']
+if obj.type == 'CURVE':
+    for subcurve in obj.data.splines:
+        curvetype = subcurve.type
+        if curvetype == 'BEZIER':
+            print("curve is closed:", subcurve.use_cyclic_u)
+            for bezpoint in subcurve.bezier_points:
+                print('knot', bezpoint.co)
+                print('handle_left', bezpoint.handle_left)
+                print('handle_right', bezpoint.handle_right)
+</code>
+==== Generieren der Daten ====
+  * https://blender.stackexchange.com/questions/6750/poly-bezier-curve-from-a-list-of-coordinates
+  * https://docs.blender.org/api/current/bpy.ops.curve.html
+Working example, adapted to blender 2.8 from https://github.com/zeffii/BlenderPythonRecipes/wiki/Curves
+<code python>
+import bpy
+from mathutils import Vector
+coordinates = [
+    ((-1, 0, 0), (-0.7, 0, 0), (-1, 0.5521, 0)),
+    ((0, 1, 0), (-0.5521, 1, 0), (0, 0.7, 0)),
+    ((0, 0, 0), (0, 0.3, 0), (-0.3, 0, 0))
+]
+def MakeCurveQuarter(objname, curvename, cList, origin=(0,0,0)):
+    curvedata = bpy.data.curves.new(name=curvename, type='CURVE')
+    curvedata.dimensions = '2D'
+    objectdata = bpy.data.objects.new(objname, curvedata)
+    objectdata.location = origin
+    bpy.context.scene.collection.children[0].objects.link(objectdata)
+    polyline = curvedata.splines.new('BEZIER')
+    polyline.bezier_points.add(len(cList)-1)
+    for idx, (knot, h1, h2) in enumerate(cList):
+        point = polyline.bezier_points[idx]
+        point.co = knot
+        point.handle_left = h1
+        point.handle_right = h2
+        point.handle_left_type = 'FREE'
+        point.handle_right_type = 'FREE'
+    polyline.use_cyclic_u = True
+MakeCurveQuarter("NameOfMyCurveObject", "NameOfMyCurve", coordinates)
+</code>
+==== Einbinden von eigenen Modulen ====
+<code python>
+# Eigene, selbstgeschriebene Bezier-Klasse
+Bezier = bpy.data.texts["bezier.py"].as_module().Bezier
+</code>
+==== Kamera animieren ====
+<code python>
+e = bpy.data.objects['Camera']
+e.animation_data_clear()
+# Loop über die frames
+    # Orthonormales system (y,-an,-vv) und Ursprung pp
+    # wobei -vv die Blickrichtung, -an nach unten zeigt und y nach rechts zeigt.
+    # matrix_world = (rechts, unten, hinten)
+    e.matrix_world = ( (y.x,y.y,y.z,1), (-an.x, -an.y, -an.z, 1),  (-vv.x,-vv.y,-vv.z,1),  (pp.x, pp.y, pp.z, 0))
+    # Rotation und Translation "keyframen"
+    e.keyframe_insert(data_path="rotation_euler", frame=frame)
+    e.keyframe_insert(data_path="location", frame=frame)
+    frame+=1
+</code>
 ==== numpy ====
 <code python>
@@ Line 51: / Line 137: @@
 print(x)  # Das geht unter Linux ins Terminal, wo Blender gestartet wurde. Keine Ahnung wohin das sonst geht...
 </code>
+===== Video kodieren =====
+<code bash>
+ffmpeg -r 30 -i %04d.png test.mkv
+</code>
+Z.B. https://fginfo.ksbg.ch/~ivo/videos/achterbahn-take1.mkv