Sketchup and Photoshop Rendering - Layer Masks

Tutorial by:

Christopher Wingate (wing0124@umn.edu)

This group of tutorials will go over how to create a rendering using Sketchup and Photoshop.

The process is based on exporting a series of images from Sketchup using Styles, overlaying them in Photoshop, and using layer masks to add realism and drama to the image.

This is part 1 of the tutorial. The rendering process makes heavy use of Photoshop's layer masks feature. If you are familiar with layer masks, please skip to the next section.

Layer Masks

Open "Layer Masks.psd"

The concept of a layer mask is simple; it allows you to control that layer's transparency. The Opacity setting in Photoshop can also control a layer's transparency, but here is the difference - it can only affect the entire image at once. If you set the Opacity of a layer to 70%, the entire image will be 70% opaque. A layer mask allows you to control the transparency of different parts of the image at the same time.

Hide the layer "Original" and show the layer "Car Removed" by clicking on the eye icon for each layer.

You will see that the car dissapears from the image. Look at the layer itself. You will see a black and white icon next to the image thumbnail. This is the layer mask. It works by being inserted into the layer and using a gradation from black to white to control the transparency of the layer. White is 100% opaque, black is 0% opaque, and shades of grey can be used to get any value of transparency in between.

Hide the layer "Car Removed" and show the layer "People Cut Out."

Now only the people are visable in the image. Look again at the layer mask. You will see that the people are white and the rest of the image is black.

Hide the current layer and show the "Gradation" layer.

Now the image's transparency is a gradation of opaque in the upper left to transparent in the lower right. The black and white gradation of the layer mask attached to the layer controls this.

Hide the current layer and show and select the "Experiement" layer.

To add a layer mask to it, make sure the layer is selected (it will be blue) and click the icon on the bottom of the layer control panel that is a white circle inside of a grey square.

To edit the layer mask, click on the mask icon on the layer, click on the paintbrush tool, select a shade of grey, and paint on the image. You will see that the transparency of the image is affected accordingly.

Hide the current layer and show the layer "Original".

To add a layer mask to a selected area, follow below.

1) Select the layer you want to add a layer mask to (layer "Original")

2) Click and hold on the lasso tool, then drag your mouse over Polygonal Lasso Tool when it pops up to select it.

3) Draw a selection. I will draw a circle around the wheel in the image.

4) With the selection active, click the layer mask icon.

Layer masks can be copied to other layers. Hide the active layer and show the "Experiment" layer. Create a new layer. Paint the entire layer red using the paint bucket.

Hold the 'Alt' key down on the keyboard, click and hold on the layer mask on the "Experiment" layer, and drag it up to the new layer ("Layer 1" by default). This will apply the mask to the red layer.

Layer masks can also be moved independently from the image they share the layer with.

1) Click on the chain icon between the layer mask and image thumbnail on "Layer 1" to unlock the layer mask's position

2) Select the Move Tool on the toolbar.

3) Click and drag on the image and you will move the layer mask accordingly.

The goal of the tutorial was to get your familiar with layer masks. Please follow the next tutorial to learn how to use layer masks when rendering with Photoshop and Sketchup.