Gradient of light

[ayeshaa23]

I've been trying to figure out how to make a gradient of light coming from a window. I want it to go from transparent to light and back to transparent but look natural. This is what I have tried to do. The light should become brighter as it goes down the page however, it should go from dark to light to dark going horizontally and I am unsure of how to achieve this. Any help is much appreciated!

[c.pfaffenbichler]

Not sure I understand; are you trying to create the direct illumination on a wall or the »bar« of light that might be produced by light hitting dust/moisture/… in the air? 

[Jumpenjax]

Duplicate the layer, then draw the angle with the polygonal lasso tool, should be a triangle, you would like to fill with the gradient. Then go to layer style, double click on your layer between the layer and the name of you layer. This will bring up your layer style box, then click on gradient overlay, pick your color you would like for the lighting. Then go back to you triangle you drew. Grab your gradient tool from your tool bar. The click on the edge of a place you would like to have the lighting start and drag to the other side of the triangle. Drag the gradient to the entire field of the triangle. You may have to play with where your starting point to achieve the correct gradation. You can also play with the the brightness to lightness in the  gradient overlay, layer style and the opacity. Hope this helps.