Re: Model View Transformation

You are not setting up the projection matrix correctly. Both the near
plane and far plane( of the view volume) should be located in the
direction in which camera is looking.
All objects outside the view volume will be culled so make sure the cube
is inside the view volume.

> Hi,
>
> I am drawing a cube (2 units on all sides)  that extends from -1 to 1 on Z
> axis. I have defined a view volume (parallel projection) that covers 3
> units
> on all sides (glOrtho (-3.0, 3.0, -3.0,3.0,-3.0,3.0). The cube faces are
> differently colored so that i know what faces i am looking
> at. The camera by default is at (0,0,0).
>
> 1) glTranslate on Z axis with 0.0, 1.0 and 2.0, i see the front face. If i
> move greater than 2.0  units, i see the back face. I am unable to explain
> this. Isn't the camera pointing towards the -Z axis at the begninning ?
> Then
> why am i seeing the front face. Then when i cross 2 units, i see the back
> face. I am unable to understand this. To see the front face, don't i have
> to
> be in front of the cube i.e something like -1.1 ? Also, for seeing the
> back
> face, don't i have to move forward at least 1.1 and then turn around ? I
> am
> confused.
>
> 2) glTranslate on Z axis with values >  4.0 or -4.0, i don't see the cube.
> I
> can see that the camera/viewpoint is  too far. What is too far ? How do i
> know that i have gone too far without trying different values ?
>
>
> Thanks for any help.
> mohan
>

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