create MuscleConstraint for driving ragdolls

interface/src/avatar/MuscleConstraint.cpp

@@ -0,0 +1,34 @@
+//
+//  MuscleConstraint.cpp
+//  interface/src/avatar
+//
+//  Created by Andrew Meadows 2014.07.24
+//  Copyright 2014 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include <SharedUtil.h>
+#include <VerletPoint.h>
+
+#include "MuscleConstraint.h"
+
+const float DEFAULT_MUSCLE_STRENGTH = 0.5f * MAX_MUSCLE_STRENGTH;
+
+MuscleConstraint::MuscleConstraint(VerletPoint* parent, VerletPoint* child)
+        : _rootPoint(parent), _childoint(child), 
+        _parentIndex(-1), _childndex(-1), _strength(DEFAULT_MUSCLE_STRENGTH) {
+    _childOffset = child->_position - parent->_position;
+}
+
+float MuscleConstraint::enforce() {
+    _childoint->_position = (1.0f - _strength) * _childoint->_position + _strength * (_rootPoint->_position + _childOffset);
+    return 0.0f;
+}
+
+void MuscleConstraint::setIndices(int parent, int child) {
+    _parentIndex = parent;
+    _childndex = child;
+}
+

interface/src/avatar/MuscleConstraint.h

@@ -0,0 +1,43 @@
+//
+//  MuscleConstraint.h
+//  interface/src/avatar
+//
+//  Created by Andrew Meadows 2014.07.24
+//  Copyright 2014 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#ifndef hifi_MuscleConstraint_h
+#define hifi_MuscleConstraint_h
+
+#include <Constraint.h>
+
+// MuscleConstraint is a simple constraint that pushes the child toward an offset relative to the parent.
+// It does NOT push the parent.
+
+const float MAX_MUSCLE_STRENGTH = 0.5f;
+
+class MuscleConstraint : public Constraint {
+public:
+    MuscleConstraint(VerletPoint* parent, VerletPoint* child);
+    MuscleConstraint(const MuscleConstraint& other);
+    float enforce();
+
+    void setIndices(int parent, int child);
+    int getParentIndex() const { return _parentIndex; }
+    int getChildIndex() const { return _childndex; }
+    void setChildOffset(const glm::vec3& offset) { _childOffset = offset; }
+    void setStrength(float strength) { _strength = glm::clamp(strength, 0.0f, MAX_MUSCLE_STRENGTH); }
+    float getStrength() const { return _strength; }
+private:
+    VerletPoint* _rootPoint;
+    VerletPoint* _childoint;
+    int _parentIndex;
+    int _childndex;
+    glm::vec3 _childOffset;
+    float _strength;    // a value in range [0,MAX_MUSCLE_STRENGTH]
+};
+
+#endif // hifi_MuscleConstraint_h