I sampled the color from the sky layer and painted to fill the gap.
Drop in the Sky3 into the Sky group. Reposition the sky. I wanted the top right portion of the image. So keeping it intact hide the remaining with a Mask.
Adjust the tone and lightness with Hue/Saturation box.
I Duplicated the background Layer. Disabled the mask, copied the portion that I wanted. Blended it using Layer Mask and Curves adjustments.
Step 4: Creating the Futuristic Building
This is what we are going to create
So we have this idea of having a giant structure in the scene based on the sketch. To create the initial shape we will use Illustrator's 3D tools. Switch to Illustrator. Press Ctrl+N to create a new document. Draw the outline shape using the Pen Tool. Change the stroke color to #ffffff
After the shape is defined go to Effect > 3D > 3D Revolve.
Copy the object and paste it into our document as Smart Object. Place it above the mountain range in the middle ground. Create a new group for the object. For the sake of simplicity call it "Building". This is going to be the base layer that contains photo elements and details.
Yeah the shape is good but I wanted it to be a little bit wider. So I stretched it a little bit by pressing Ctrl+T. Add a Layer Mask to the base layer and hide the areas that are covering the trees in the background to make it look like it is behind the trees.
Recolor the building. Create a new layer above the base layer. Press Ctrl+Alt+G to clip the layer to the base layer. Create a new gradient in with similar values. Apply the gradient by dragging with the Gradient tool.
Lower the opacity of the layer to 50%.
Open the building stock and remove the sky using the Magic Wand Tool.
Set a vertical guide. Press Ctrl+T and rotate the building to align with the vertical guide. Make a selection, copy and paste into the main file.
Now clip the layer to the base layer. Flip the layer horizontally.
I stretched and squeezed the layer quite drastically. Try to get it right in one attempt. If you back and forth the image will loose data and blurs.
We will use the middle portion of the image. Hide remaining with a Layer Mask.
Adjust the colors and remove that green shades using Curves and Hue/Saturation.
The image is evenly lit. So paint a dark color on the shadow side of the building. Create a new layer above the current layer. Just sampled a dark tone from the background and painted with a large soft brush. The red color in the below image indicates the painted region.
Adjust the highlights slightly. Click back on the photo element, press "Q" to enter quick mask mode paint over the right edge with around 50% brush opacity. Press "Q" again to exit the quick mask mode. Invert the selection by pressing Ctrl+Shift+I, adjust the highlights slightly.
Deselect the selection. Reduce the saturation of the layer.
Create a new layer and paint a shadow. Clip to the base layer.
The lighting isn't strong enough. Paint a lighter color with a soft brush. I painted with 50% opacity setting.
Add fine details. I picked a 1 pixel brush to paint subtle highlights and shadows. Spend some time to get it right.
Paint structural details. Pick a small brush to paint details.