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Directional Light From Camera

Started by MatthewEva Mar 30, 2004 at 5:33 AM 1 replies 650+ views

Original Post

Mar 30, 2004 at 5:33 AM

Hi, Im having a little trouble with matrices. I have set up a view matrix that I am spinning around using the mouse. However, What I want to do is set up a directional light pointing towards where I am facing (the view). so I have a D3DXMATRIX member variable representing the current view matrix. I use this in the SetTransform(..) so I know the matrix is getting changed ok. Once I change the view, what I need to know is how to obtain the vector facing the direction of the view. Imagine you are a camera on the end of a torch, I need to find the direction vector required to set the directional light. i.e. 0.0f 1.0f 0.0f if my cam is pointing along the y axis. Is there an easy way to obtain this vector, I dont know too much about Dot Products, or cross products, are these the key to what I am looking for? Hope you can help

[edited by - MatthewEva on March 30, 2004 8:19:29 AM]

neneboricua19

Mar 30, 2004 at 12:49 PM

You can get the camera''s view vector directly from the view matrix:

direction.x = view._13;
direction.y = view._23;
direction.z = view._33;

In general, you can get a bunch of info from the view matrix:

right.x = view._11;
right.y = view._21;
right.z = view._31;
up.x = view._12;
up.y = view._22;
up.z = view._32;
direction.x = view._13;
direction.y = view._23;
direction.z = view._33;

Hope this helps,
neneboricua

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