# Signal return vector

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Hi guys

In the attached graphic, I am trying to figure out how much of the signal will return to the source based on signal vector and surface normal.
For the purposes of this example, assume that the horizontal angle between the Z axis and the point from the source is -30°(ie to the left), and that the vertical angle between the Y axis and the point from the source is -15° (ie down). The signal (or "light") is pointing directly at the point. How would I set up the signal vector? I take it this is kindof like calculating the dot product between a vertex point and the view/projection matrix. Any suggestions?

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Would I be correct in building a 3D rotation matrix based on a light vector length of 1? How would I build this matrix in HLSL? I am already familiar with the float2x2 rotation = {cos, -sin, sin, cos};.

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