CODEWITHSUNDEEP
openglrotationmatrix-multiplicationoculusglulookat
kevin0228ca
kevin0228ca

Reputation: 489

Rotate camera in own coord using gluLookat and glMultMatrixf

I have to change a camera implementation built with gluLookat and glMultmatrixf.

The camera implemented is an arcball camera where the camera rotates around a point.

Orientation of the camera is by

//set projection
glMatrixMode(GL_PROJECTION);
gluPerspective (..);
//modelview
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

gluLookAt(pCamera.x, pCamera.y, pCamera.z,
          pTarget.x, pTarget.y, pTarget.z,
          up.x, up.y, up.z);

And is followed by

glMultMatrixf(transformViewMatrix);

to move the camera around the point, where transformViewMatrix is calculated from mouse coord

I have to integrate Oculus Rift with the camera so the camera can rotate on spot instead of around a point.

I can get a rotation matrix from Oculus sensor, rotOculus.

I tried multiplying transforViewMatrix with rotOculus.

glMultMatrixf(transformViewMatrix*rotOculus);

but get that the object I am looking at is rotating on spot instead of the camera

then I tried to assign transformViewMatrix with rotOculus, but that is same as arcball rotation with mouse, just changed to Oculus.

I think in order to rotate camera on spot, I need to translate the camera to origin by pCamera, then glMultMatrixf(rotOculus)?

But I dont have access to how I can order glTranslate, gluLookAt, glMultMatrixf methods because those are implemented in a dll, I can only change pCamera, pTarget, up, and viewTransformMatrix.

Could anyone point how I could rotate camera on spot in this situation? Thank you.

Upvotes: 1

Views: 743

Answers (1)

Jherico
Jherico

Reputation: 29240

You want to move the lookat vector, which is the line between pCamera and pTarget. You don't specify what types you're using, but the code should look something like this

// Get the lookat vector
vec3 lookAtVector = pTarget - pCamera;
// Rotate by the HMD orientation
lookAtVector = rotOculus * lookAtVector;

// Add back the camera vector to get the worldspace target
vec3 newTarget = lookAtVector + pCamera;

// Upload the view matrix to GL
gluLookAt(pCamera.x, pCamera.y, pCamera.z,
         newTarget.x, newTarget.y, newTarget.z,
         up.x, up.y, up.z);

Upvotes: 1

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