The Sims 3: Extracting a sim from background
This guide will explain how to extract a sim from its background using layer masks. It takes less than 5 minutes and does not involve the Lasso or Pen tools! This is written with Photoshop CS6 in mind, but I’m assuming it’ll work with any graphics editing program that supports alpha channels. The starting point for working on this was buhudain‘s tutorial here.
First of all, you will need to take two images of your Sim in the exact same position. One will have a white background, and the other will have a black one. To make this easier, I recommend using a camera mod and the buydebug lights to ensure that the lighting is level. These are the two images I’ll be using:
And you can see that I got kinda lazy with the white one, haha.
Open them both within the same document in Photoshop and unlock them. Place the black BG one (I named it ‘BLACK’) above the white BG one (named ‘WHITE’), then duplicate one of them (doesn’t matter which; I named it ‘BASE’). Your layer structure should look like in the screenshot to the right.
Select the BLACK layer and set its blending mode to ‘Difference’. Your Sim should now be completely black (or very dark), while the background should be white (or very light).
Merge the BLACK and WHITE layers (I named the resulting layer, ‘MASK’). Now, we’re going to work on the alpha channel. The gist of it is that you can only paint in black, white or gray on the alpha channel, and this will translate to transparency. Absolute white means completely opaque, while absolute black means complete transparency.
In this case we want to extract the Sim, so it needs to be opaque (white). You’ll notice that the picture shows the complete opposite, and also that the background isn’t absolute white, but a light gray - which would result in partial transparency. We’ll need to fix that before touching the alpha channel.
With the MASK layer active, go to Image \ Adjustments \ Brightness/Contrast and set both of them to 50.
Then, go to Image \ Adjustments \ Invert and voilà, your image is now black & white and the Sim is correctly covered in white.
Now it’s finally time to get to work on the alpha channel 😊
Hit Ctrl-A to select your entire MASK layer, and Ctrl-C to copy its contents. You can now hide the MASK layer, as we will be working on the BASE one. Select the BASE layer, then switch over to the Channels tab (if you can’t see it, enable it in Window \ Channels) and create a new channel, like in the image to the right.
It will be called ‘Alpha 1′. Select this channel and hit Ctrl-V to paste the mask on it. The other channels - Red, Green, Blue - will show your image in different states, but the Alpha channel will show your Sim as completely white, over a black (well, dark red) background.
Ctrl-click on the Alpha channel to make a selection of your Sim. You can fine-tune it in Select \ Modify or using the Quick Selection Tool (press W), but it’s usually fairly accurate. If you aren’t happy with the selection, go back to when we edited the brightness and contrast and lighten/darken parts of your mask manually.
Now that you have your selection, click on the RGB channel, then return to the Layers window and select the BASE layer. Go to Layer \ New \ Layer Via Cut (or press M to select the Rectangular Marquee Tool, then right-click on the layer and select “Layer Via Cut”).
The result will be a new layer with your render! You can now delete the other layers and the alpha channel and import other images to use as background for your Sim :)
