Hi guys,

I want to share my solution to the problem of positioning and rotating 3D-objects from jPCT-AE with OpenGLs Model-View Matrix (e.g. Vuforia tracking data) because I was asked to give help concerning this topic.

A picture of the Model-View Matrix and its components is attached. I created this picture as a part of my bachelor thesis.

A little warning:

I haven't used jPCT-AE with Vuforia for more than 2 years

Furthermore, the code snippets are simpified.

You can get the Model-View Matrix by tracking markers with the Vuforia SDK. The tracking data will be used to show 3D-objects on the marker:

In the onDrawFrame-Method I apply the origin (position) of the Object3D-object via a SimpleVector by using the Translation-Vector of the Model-View Matrix

`mSimpleVector.set(modelViewMat[12], modelViewMat[13], modelViewMat[14]);`

myObject.setOrigin(mSimpleVector);

After that I apply the rotation by converting the Model-View-Matrix float-array to a RotationMatrix:

`myObject.setRotationMatrix(ArrayToMatrix(modelViewMat));`

`protected Matrix ArrayToMatrix(float array[]) {`

// Declare variables

float[] insertDump = new float[16]; // The array holding the values in

// the new Matrix

int targetElement = 0; // Points to the next location in the insertDump

// to add data

// Loop through the rows of the Matrix3f

for (int sourceRow = 0; sourceRow < 3; sourceRow++) {

// Insert the 3 elements from the Matrix3f into the Matrix. The

// fourth element has been initialized to 0.0f.

insertDump[targetElement] = array[targetElement];

insertDump[targetElement + 1] = array[targetElement + 1];

insertDump[targetElement + 2] = array[targetElement + 2];

// Move the target ahead by four spaces

targetElement += 4;

}

// The final row consists of { 0.0f, 0.0f, 0.0f, 1.0f }, since this is a

// rotation matrix

insertDump[15] = 1.0f;

// Create the new Matrix and load in the values

Matrix output = new Matrix();

output.setDump(insertDump);

// Return

return output;

}

In my finished project I have a two-dimensional array of 16 Model-View Matrices, so I can place 3DObjects on up to 16 Vuforia Markers. That's why my original code would be too complicated.

My project, which I developed as a part of my bachelor thesis, shows 3D-Letters on the markers, so that the user can put them together to an existing word. (see the following YouTube-Link)

https://www.youtube.com/watch?v=NdI_7Ky8XTsIf you have more questions concerning that topic, you can ask me. But I have to repeat my warning: I haven't used jPCT-AE with Vuforia for more than 2 years

If any important information is missing, please tell me.

Happy coding

Shizzn