Egon, I've been stuck for six months on the very last step of importing a GLB model. When I try to animate the (otherwise perfect) model, it gets all messed up. I'm assuming the skeletal calculations are accurate, so could you please verify that this Keyframe class is accurately converting between the Glb coordinate system and jpct's?
class Keyframe {
private double time;
private Matrix transform;
public Keyframe(double time, Matrix transform) {
this.time = time;
// Normalize the rotation component of the transform
Quaternion rotation = new Quaternion(transform); // Extracts the rotational component
rotation.normalize();
Matrix rotationMatrix = rotation.toMatrix();
// Adjust the transform to the jPCT coordinate system
this.transform = adjustToJpctCoordinateSystem(rotationMatrix);
// Extract and reset translation
SimpleVector translation = extractTranslation(transform);
resetTranslation(transform);
// Extract, check, and apply uniform scale
SimpleVector scale = extractScale(transform);
if (!isUniformScale(scale)) {
scale = new SimpleVector(1f, 1f, 1f); // (1, 1, 1) Use uniform scale if it's not uniform
}
Utilities.setScale(this.transform, scale);
// Combine rotation and scale, reapply translation
this.transform = combineTransforms(translation, this.transform, scale);
}
// Method to adjust a transformation matrix to jPCT's coordinate system
private Matrix adjustToJpctCoordinateSystem(Matrix transform) {
Matrix adjustedMatrix = new Matrix(transform);
// Flip the Y-axis
adjustedMatrix.set(1, 0, -adjustedMatrix.get(1, 0));
adjustedMatrix.set(1, 1, -adjustedMatrix.get(1, 1));
adjustedMatrix.set(1, 2, -adjustedMatrix.get(1, 2));
// If there's translation on Y-axis, flip it as well
adjustedMatrix.set(1, 3, -adjustedMatrix.get(1, 3));
// Flip the Z-axis
adjustedMatrix.set(2, 0, -adjustedMatrix.get(2, 0));
adjustedMatrix.set(2, 1, -adjustedMatrix.get(2, 1));
adjustedMatrix.set(2, 2, -adjustedMatrix.get(2, 2));
// If there's translation on Z-axis, flip it as well
adjustedMatrix.set(2, 3, -adjustedMatrix.get(2, 3));
return adjustedMatrix;
}
public double getTime() {
return time;
}
// Extract the translation component from a transformation matrix
private SimpleVector extractTranslation(Matrix transform) {
return new SimpleVector(transform.get(3, 0), transform.get(3, 1), transform.get(3, 2));
}
public Matrix getTransform() {
return transform;
}
// Reset the translation component of a transformation matrix to zero
private void resetTranslation(Matrix transform) {
transform.set(3, 0, 0);
transform.set(3, 1, 0);
transform.set(3, 2, 0);
}
// Helper method to extract scale from a transformation matrix
private SimpleVector extractScale(Matrix transform) {
// Assuming the scale is represented by the length of the axis vectors in the matrix
SimpleVector scaleX = new SimpleVector(transform.get(0, 0), transform.get(1, 0), transform.get(2, 0));
SimpleVector scaleY = new SimpleVector(transform.get(0, 1), transform.get(1, 1), transform.get(2, 1));
SimpleVector scaleZ = new SimpleVector(transform.get(0, 2), transform.get(1, 2), transform.get(2, 2));
return new SimpleVector(scaleX.length(), scaleY.length(), scaleZ.length());
}
// Combine the translation, rotation, and scale into a single transformation matrix
private Matrix combineTransforms(SimpleVector translation, Matrix rotation, SimpleVector scale) {
Matrix scaleMatrix = new Matrix();
scaleMatrix.setIdentity();
Utilities.setScale(scaleMatrix, scale);
Matrix combined = new Matrix();
combined.setIdentity();
combined.matMul(rotation);
combined.matMul(scaleMatrix);
combined.translate(translation);
return combined;
}
// Helper method to check if the scale is uniform
private boolean isUniformScale(SimpleVector scale) {
// Check if all components are the same within a small epsilon to account for floating-point precision
final float epsilon = 0.0001f;
return Math.abs(scale.x - scale.y) < epsilon && Math.abs(scale.y - scale.z) < epsilon;
}
// Method to apply scale to a transformation matrix
private void applyScaleToTransform(Matrix transform, SimpleVector scale) {
// Reset the scale component of the matrix to 1
for (int i = 0; i < 3; i++) {
float length = new SimpleVector(transform.get(0, i), transform.get(1, i), transform.get(2, i)).length();
if (length != 0) { // Avoid division by zero
transform.set(0, i, transform.get(0, i) / length);
transform.set(1, i, transform.get(1, i) / length);
transform.set(2, i, transform.get(2, i) / length);
}
}
// Create a scale matrix
Matrix scaleMatrix = new Matrix();
scaleMatrix.setIdentity(); // Start with an identity matrix
scaleMatrix.set(0, 0, scale.x);
scaleMatrix.set(1, 1, scale.y);
scaleMatrix.set(2, 2, scale.z);
// Apply scale by multiplying the existing transform with the scale matrix
transform.matMul(scaleMatrix);
}
}
