The Vanishing Point Filter is another one of those hidden gems in Photoshop.  Basically, you define a 3D-wire-frame and have Photoshop use it as a guide.  Sure, you can Clone in this 3D space, but did you know that you can Copy-and-Paste also?  Take a look at the Before and After pictures below.  I used the Vanishing Point Filter to add the cloud reflections to the windows.

1. Prepare file in Photoshop

In Photoshop, I duplicated the original layer for use in the Vanishing Point Filter.  I also selected the portion of the clouds to be used as the reflection source.  This selection must be Copied (Control-C or Command-C) BEFORE you launch the Vanishing Point Filter located in the Filters drop-down menu.

2. Create the 3D Plane

Using the Create Plane Tool, I set four points to define the first plane.  Photoshop automatically defines a grid around these four points.  You can use the Edit Plane Tool to tweak these 4 points.

3. Paste selection into Vanishing Point Filter

With the Plane defined, simply Paste (Control-V or Command-P) into the Vanishing Point Filter.  The selection will appear as a floating layer in the upper left corner.

4. Drag selection onto Plane

Now, it is just a matter of dragging the pasted selection onto the Plane.  I then used the Transform Tool to edit the selection to fill the Plane.  Once completed, I just clicked OK to apply the Vanishing Point Filter to the duplicate layer.

5. Finish in Photoshop

The Vanishing Point Filter does not have Opacity Controls to vary the strength of this tools.  That is why I created a duplicate layer specifically for this effect.  I used the Layer Blend mode to vary the strength of the layer.  Soft Light blending works perfectly to create reflections.  I just fine-tooled the effect by adding a Layer Mask to only reveal the portion covering the windows.

The final effect in very natural.

Tomorrow, I will cover another variation on the Vanishing Point Filter.