Initial Commit

lottie/utils/ik.py

@@ -0,0 +1,97 @@
+from..nvector import NVector
+
+
+# FABRIK
+class Chain:
+    def __init__(self, tail, fixed_tail=True, tolerance=0.5, max_iter=8):
+        self.joints = [tail.clone()]
+        self.fixed_tail = fixed_tail
+        self.lengths = []
+        self.total_length = 0
+        self.tolerance = tolerance
+        self.max_iter = max_iter
+
+    def add_joint(self, point):
+        length = (point - self.joints[-1]).length
+        self.lengths.append(length)
+        self.total_length += length
+        self.joints.append(point.clone())
+
+    def add_joints(self, head, n):
+        delta = head - self.joints[-1]
+        self.total_length += delta.length
+        segment = delta / n
+        seglen = segment.length
+        for i in range(n):
+            self.lengths.append(seglen)
+            self.joints.append(self.joints[-1] + segment)
+
+    def backward(self, target):
+        """!
+        target -> -> start
+        """
+        self.joints[-1] = target
+        for i in range(len(self.joints)-2, -1, -1):
+            r = self.joints[i+1] - self.joints[i]
+            l = self.lengths[i] / r.length
+            self.joints[i] = self.joints[i+1].lerp(self.joints[i], l)
+
+    def forward(self, target):
+        """!
+        start -> -> tail
+        """
+        self.joints[0] = target
+        for i in range(0, len(self.joints)-1):
+            r = self.joints[i+1] - self.joints[i]
+            l = self.lengths[i] / r.length
+            self.joints[i+1] = self.joints[i].lerp(self.joints[i+1], l)
+
+    def reach(self, target):
+        if not self.fixed_tail:
+            self.backward(target)
+            return
+
+        distance = (target - self.joints[0]).length
+        if distance >= self.total_length:
+            for i in range(len(self.joints)-1):
+                r = target - self.joints[i]
+                l = self.lengths[i] / r.length
+                self.joints[i+1] = self.joints[i].lerp(target, l)
+            return
+
+        base = self.joints[0]
+
+        distance = (target - self.joints[-1]).length
+        n_it = 0
+        while distance > self.tolerance and n_it < self.max_iter:
+            self.backward(target)
+            self.forward(base)
+            distance = (target - self.joints[-1]).length
+            n_it += 1
+
+
+class Octopus:
+    def __init__(self, master):
+        self.chains = {"master": master}
+        self.master = master
+
+    @property
+    def base(self):
+        return self.master.joints[-1]
+
+    def add_chain(self, name):
+        ch = Chain(self.base)
+        self.chains[name] = ch
+        return ch
+
+    def reach(self, target_map):
+        centroid = NVector(0, 0)
+        for chain, target in target_map.items():
+            self.chains[chain].backward(target)
+            centroid += self.chains[chain].joints[0]
+        centroid /= len(target_map)
+
+        self.master.reach(centroid)
+
+        for chain in target_map.keys():
+            self.chains[chain].forward(self.base)