[osg-users] How to extend my screen space handling to z-direction?

[Charma Man]

Hi osg-community,

I am working on a stereoscopic renderer which can receive mouse and 
on-screen-touch-events to handle translations of the scene. Now I want to 
extend this to handle gestures of the Xbox-Kinect camera. I already got it 
working for the x and y on-screen translation. Unfortunatly I don't know how to 
handle movements of the z-direction (towards/into the screen). I already ensure 
that my coordinates from my kinect-camera are scaled from -1 to 1 for all 
directions.

Here is the code that is already working for X and Y directions. I have tried 
to extend (commented out) it for the Z direction but couldn't get it to work. 
Maybe someone has any idea how to do it. My implementation for the z-direction 
was a complete guess, so it is possible that I am way off.


Code:

double dist = opencover::cover-getViewerScreenDistance();

//
// The center is (0.5, 0.5) only if the viewer position is exactly in the 
middle
// of the screen
// On the table, we are way more nearer to the bottom, thus, the center is 
calculated
// dynamically. This way, head-tracking is possible
//
double horzFrustum = this-frustum.right + fabsf(this-frustum.left  );
double vertFrustum = this-frustum.top   + fabsf(this-frustum.bottom);
//double forwardFrustum = fabsf(this-frustum.zfar) + 
fabsf(this-frustum.znear);

//
// For stereo, we are interacting on the screen surface and not on the near 
plane,
// thus calculate the motion on the surface
//
double surfaceRight = (horzFrustum / 2.0f) * dist / this-frustum.znear;
double surfaceTop   = (vertFrustum / 2.0f) * dist / this-frustum.znear;
//double surfaceFar   = (forwardFrustum / 2.0f) * dist / 
this-frustum.znear;

double screenCenterX = this-frustum.right / horzFrustum;
double screenCenterY = this-frustum.top   / vertFrustum;
//double screenCenterZ = this-frustum.zfar  / forwardFrustum;

//
// Compute x0 and y0 in world coords using the theorem on intersecting lines
//
double x0 = (cur.down.x() - screenCenterX) * 2.0 * surfaceRight;
double y0 = (cur.down.y() - screenCenterY) * 2.0 * surfaceTop;
//double z0 = (cur.down.z() - screenCenterZ) * 2.0 * surfaceFar;

//
// Compute xc and yc in world coords using the theorem on intersecting lines
//
double xc = (cur.curr.x() - screenCenterX) * 2.0 * surfaceRight;
double yc = (cur.curr.y() - screenCenterY) * 2.0 * surfaceTop;
//double zc = (cur.curr.z() - screenCenterZ) * 2.0 * surfaceFar;

//
// Compute translation
//
osg::Vec3 direction = Vec3(xc-x0, zc-z0, yc-y0);

//
// Get the viewer position
//
osg::Vec3 viewerPosition = opencover::cover-getViewerMat().getTrans();

//
// Compute new transform matrix
//

osg::Matrix transform =
this-rootTransform
* osg::Matrix::translate(-viewerPosition)
* osg::Matrix::translate(direction)
* osg::Matrix::translate(viewerPosition);

//
// Apply the new transformation matrix -- if it's valid
//
if (transform.valid())
{

opencover::VRSceneGraph::instance()-getTransform()-setMatrix(transform);
}




variable cur.down is where the cursor of mouse started clicking / touch on 
the screen first appeared / kinect started captureing the skeleton
variable cur.curr is the current position of the corresponding cursor 
(mouse/touch/kinect).

I hope someone can help!

Thank you!

Cheers,
Charma

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http://forum.openscenegraph.org/viewtopic.php?p=52065#52065





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[osg-users] How to draw a simple frustum wireframe cube?

[Charma Man]

Hello Forum,

I am an absolute osg-beginner. I am currently working on a very huge project 
which is using osg. I now would like to draw something in the existing scene 
without messing everything up. I will try to give you as much detail as I can 
to make it easier to understand.

I have access to a callback-function which is called before every frame 
drawing. Also I have access to the two matices


Code:
this-rootTransform = opencover::cover-getObjectsXform()-getMatrix();

// Get camera frustum parameters
osg::Matrix matProj = 
opencover::coVRConfig::instance()-screens[0].camera-getProjectionMatrix();

matProj.getFrustum(
this-frustum.left,
this-frustum.right,
this-frustum.bottom,
this-frustum.top,
this-frustum.znear,
this-frustum.zfar
);




As you probably see the call opencover::coVRConfig::instance() also returns the 
instance. What I would like to do now is draw some simple lines (as in like 
glBegin) but in screen coordinates, so with positions in the frustum corners 
like (1,1,1) or (1,-1,-1).

The reason for this is that I want to make the whole frustum visible because 
I am using a stereoscopic VR-renderer and I want to validiate how big the 
frustum is and when do you step into the 3D scene.

I hope anyone can help me with this and can provide some simple sample code. If 
you need more detail, feel free to ask back.

Thank you!

Cheers,
Charma

--
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=50045#50045





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