08-13-2004, 09:38 AM

Can someone help me,

I have a problem when I try to get the origin of an object in world space coordinates.

For example I have a sphere wich moves along Y axis, parallel to it (x = 0, z = 0, Z means UP, Y means DEPTH)

The projection is perspective :

gluPerspective(70.0, (float)w / (float) h, 0.08, 4.0);

Camera position is defined as follows:

gluLookAt(0.0, -0.2, 0.25, 0.0, 0.3, 0.0, 0.0, 0.0, 1.0);

I get the sphere's center location using the following code :

glGetDoublev (GL_MODELVIEW_MATRIX, modelviewMatrix);

x = modelviewMatrix[12];

y = modelviewMatrix[13];

z = modelviewMatrix[14];

When the sphere's center Y value becomes less then 0, Z value of the sphere's center starts to decrease. Nevertheless the sphere continues to move parallel to the Y axis.

The problem is why Z value changes ?

Another point is when I change the position of the camera (Z value) I receive different values for x,y and z, despite the object location is the same.

Regards!

I have a problem when I try to get the origin of an object in world space coordinates.

For example I have a sphere wich moves along Y axis, parallel to it (x = 0, z = 0, Z means UP, Y means DEPTH)

The projection is perspective :

gluPerspective(70.0, (float)w / (float) h, 0.08, 4.0);

Camera position is defined as follows:

gluLookAt(0.0, -0.2, 0.25, 0.0, 0.3, 0.0, 0.0, 0.0, 1.0);

I get the sphere's center location using the following code :

glGetDoublev (GL_MODELVIEW_MATRIX, modelviewMatrix);

x = modelviewMatrix[12];

y = modelviewMatrix[13];

z = modelviewMatrix[14];

When the sphere's center Y value becomes less then 0, Z value of the sphere's center starts to decrease. Nevertheless the sphere continues to move parallel to the Y axis.

The problem is why Z value changes ?

Another point is when I change the position of the camera (Z value) I receive different values for x,y and z, despite the object location is the same.

Regards!