# camera

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Hi, To orbit around an object in y direction, how should I modify my up vector. [Edited by - tinu on March 26, 2007 1:28:53 AM]

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You don't. If you use a look-at matrix, set the look-at vector to your object, and move your camera in a circle around the object.

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How to
move camera in a circle around the object.

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You google for some basic matrix mathematics. Are you sure you want to rotate the camera around the object, and not rotate the object on the spot?

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s.I need to rotate the camera around the object.

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D3DXMatrixLookAtLH() will do the job then, and you can just have the camera position move in a circle as:
D3DXVECTOR3 vPos(sin(angle), 0.0f, cos(angle)); where angle is the angle you want to use, which will be incrementing each frame.

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Given an angle and a radius, you can use some simple trig to determine the X and Y position.

                             Camera                             +                            /|                          /  |                 radius /    |                      /      |                    /        | Y                  /          |                /           _|              / theta      | |             +---------------+         Object      X

SOHCAHTOA

You'll need to modify the axes to rotate on the Y axis (for simplicity this is an example of rotating on the Z axis).

EDIT: Yeah, what Evil Steve said.

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Yes.
This is true in orbiting in x-direction
But to orbit in y direction what should i do?

z = Radius * cos( Angle );
y = Radius * sin( Angle );

Is this correct?

If I do this,At particular angles my object disappears.

To avoid this, should I modify my up vector also?

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Quote:
 Original post by tinuYes.This is true in orbiting in x-direction But to orbit in y direction what should i do?z = Radius * cos( Angle );y = Radius * sin( Angle );Is this correct?If I do this,At particular angles my object disappears.To avoid this, should I modify my up vector also?
To orbit around the Y axis, you modify X and Z. You only change the up vector if the "up" direction has changed - which is if you rotate the camera around either X (Pitch) or Z (roll).

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To rotate the camera around X axis (pitch as mentioned)
how should i modify my up vector

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