Tidy up and get IK working

[opengl.git] / ik.cpp

diff --git a/ik.cpp b/ik.cpp
index 3895efe7819abdf8a546691f5b436645fd1ac02e..9598ddc870ee0d45b3d8d322ba87aa696d4f3391 100644 (file)
--- a/ik.cpp
+++ b/ik.cpp
@@ -70,7 +70,7 @@ vec3 extractPos(mat4 trans) {
        return vec3(trans[3]);
 }
 
-glm::mat4 absoluteToModelSpace(const Model::Node &root, const Model::Node &n, mat4 m) {
+mat4 absoluteToModelSpace(const Model::Node &root, const Model::Node &n, mat4 m) {
        const Model::Node *parent = &n;
        glm::mat4 res = m;
        std::vector<mat4> trans;
@@ -96,18 +96,24 @@ mat4 getRotationToPoint(vec3 u, vec3 v, float dist) {
        return res;
 }
 
+// Normalizes a transformation matrix to not have any scale factor
+inline mat4 normalizeScale(mat4 m) {
+       for (int i = 0; i < 3; i++)
+               m[i] = normalize(m[i]);
+       return m;
+}
+
 float d = 0;
 
 // Target is world position
-void inverseKinematic(Model::Node &start, Model::Node &end, vec3 target) {
+void inverseKinematics(Model::Node &start, Model::Node &end, vec3 target) {
        std::vector<Model::Node> chain = allNodesTo(start, end);
        assert(!chain.empty());
 
-       const Model::Node *rootPtr = start.parent;
-       while (rootPtr->parent != nullptr)
-               rootPtr = rootPtr->parent;
-       const Model::Node &root = *rootPtr;
+       // Calculate the world root
+       const Model::Node &root = start.getRoot();
 
+       // Work out the positions and distances
        std::vector<vec3> positions(chain.size()); std::vector<float> distances(chain.size() - 1);
        for (size_t i = 0; i < chain.size(); i++) {
                mat4 absTrans = getAbsTrans(root, chain[i]);
@@ -116,10 +122,9 @@ void inverseKinematic(Model::Node &start, Model::Node &end, vec3 target) {
                        distances[i - 1] = distance(positions[i], positions[i - 1]);
        }
 
+       // Do the actual IK part
        auto newPositions = fabrik(target, positions, distances);
        
-
-       
        // Move all the nodes so that they are in the correct positions
        // Don't need to move the root node - it's already in place
        for (size_t i = 1; i < chain.size(); i++) {
@@ -127,26 +132,19 @@ void inverseKinematic(Model::Node &start, Model::Node &end, vec3 target) {
                mat4 absTrans = getAbsTrans(root, node);
                absTrans[3] = vec4(newPositions[i], absTrans[3][3]); // update position in transform
                
-               /* vec3 oldRelPos = extractPos(aiMatrixToMat4(node.ai.mTransformation)); */
-               /* vec3 newRelPos = extractPos(absoluteToModelSpace(root, *node.parent, absTrans)); */
-               /* mat4 rot = getRotationToPoint(oldRelPos, newRelPos, distances[i - 1]); */
-               /* node.ai.mTransformation = mat4ToaiMatrix(rot * aiMatrixToMat4(node.ai.mTransformation)); */
-
-               absTrans[3] = vec4(newPositions[i], absTrans[3][3]); // update position in transform
-               
                mat4 relTrans = absoluteToModelSpace(root, *node.parent, absTrans);
                node.ai.mTransformation = mat4ToaiMatrix(relTrans);
        }
 
        // Now rotate all the nodes so that they point towards each other
        // Don't need to rotate the last node - it has nothing to point towards
-       // FIXME: This is numerically unstable and the transformation scales over time!!!
+       // FIXME: Despite normalizeScale, this is still numerically unstable
+       // and the transformation scales over time!!!
        for (size_t i = 0; i < chain.size() - 1; i++) {
                auto node = chain[i]; auto nextNode = chain[i + 1];
                mat4 oldTrans = aiMatrixToMat4(node.ai.mTransformation);
                vec3 nextNodePos = extractPos(aiMatrixToMat4(nextNode.ai.mTransformation));
 
-
                vec3 up = {0, 1, 0};
                vec3 dir = -normalize(nextNodePos);
 
@@ -156,11 +154,14 @@ void inverseKinematic(Model::Node &start, Model::Node &end, vec3 target) {
                                                  -v[1], v[0], 0);
                mat4 rot = mat3(1) + sscpm + sscpm * sscpm * (1.f / 1.f + dot(up, dir));
 
-
+               // very important that we normalize the scale
+               // otherwise we end up with gradually growing models
+               // due to numerical instabaility
+               rot = normalizeScale(rot);
                node.ai.mTransformation = mat4ToaiMatrix(oldTrans * rot);
 
                for (auto child: node.getChildren()) {
-                       child->ai.mTransformation = mat4ToaiMatrix(inverse(rot) * aiMatrixToMat4(child->ai.mTransformation));
+                       child->ai.mTransformation = mat4ToaiMatrix(normalizeScale(inverse(rot)) * aiMatrixToMat4(child->ai.mTransformation));
                }
 
        }