Author Topic: GLB  (Read 3438 times)

Offline AGP

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GLB
« on: November 14, 2023, 09:39:01 am »
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?

Code: [Select]
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);
    }
}

Offline EgonOlsen

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Re: GLB
« Reply #1 on: November 14, 2023, 10:21:47 am »
I'm not sure...I assume that the format is the same as the one that OpenGL uses? In that case, have you tried to use Matrix.transformToGL() instead? Despite the name, it actually transforms jPCT into GL and back again. Comparing what these two methods do, it looks like as if yours does somehow a "flipped" version of what jPCT's is doing. Like as if it's working on an inverse instead , but I'm not sure...it might be worth a try to give jPCT's method a shot, though.
« Last Edit: November 14, 2023, 12:26:12 pm by EgonOlsen »

Offline AGP

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Re: GLB
« Reply #2 on: December 19, 2023, 11:20:24 pm »

Offline EgonOlsen

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Re: GLB
« Reply #3 on: December 21, 2023, 06:56:41 am »
Nice one!