A 2026 Guide to the Emission Map (And How to make things Glow)

A lot of the emission layer guides I've come across are quite old, generally unclear with some missing or vaguely-explained steps, and some of them have the wrong dimensions listed for the size of the emission map in relation to the type of CAS object that's being edited.

I have wanted to make an up-to-date Emission map guide for a long time that is in-depth, clearer, and in more broken-down steps. I originally learned from the rough tutorials about it on Sims 4 Studio, but they are older and refer to things we don't need to do anymore to import the option for an Emission map into a .package, amongst other things.

I will also cover a completely unexpected snag I hit in the making of this tutorial and will explain the issue that I eventually found in CAS tools hours after I'd fixed every other possible issue. 

This is a guide to the Emission map that makes CAS content glow, and how to edit it to make glowing or flashing designs on CC! This is will also explain the application of the design to the T-shirt texture using GIMP, for completion's sake, as well as a few ways you can clean up the design a bit beforehand.

FLASHING WARNING: I'm not sure if this requires a warning, but later on on the section about controlling the fade in-out glow, there is a gif which shows the pawprint design on the T-shirt flashing from bright to dim 4 times in 4 seconds. It's not super quick, but the warning is here.
There is also a .gif of many stars flashing at different speeds, but no faster than the 100% white Alpha channel pawprint .gif.

 

YOU WILL NEED:

- Sims 4 Studio (up-to-date, the current Open Beta version as of 20/04/26 is 3.2.6.1 (Star)
- GIMP (I use version 3.0.4). 
- CAS Tools
- All of the steps in this tutorial can be done in Photoshop instead of GIMP, so if you know how to use Photoshop you can use it for all the same steps. GIMP is my go-to hence the focus in this guide.
- A 2d design, pattern or drawing that you want to make glow on a CAS object. I recommend using a single-colour design (like a silhouette) or lineart for this. For the first part of this tutorial I am using a paw print.

The CAS Tools parts here are something I learned from Cmar's emission map guide

Save frequently, and save multiple copies! As you go, make sure you SAVE a separate file after every numbered step. Ideally, you want to have these as separate files:

- The unedited Diffuse texture
- The Diffuse texture with your design on it
- The .xcf file (or .psd file in Photoshop) that has your Design on one layer, and the Diffuse texture from Sims 4 Studio on the other
- Your Emission map texture, saved as .png BEFORE you edit the Alpha Channel
- the Emission map as a .dds file 

 

What is the Emission Map?

The Emission map is a sort of texture map in Sims 4 that controls any glowing light on a Sims 4 CAS object.
An example of something with an Emission map is the Logitech headset, which has glowing parts on it, or the Vampires pack's eyes that glow.

 

The fading in and out of the glowing is controlled by editing the Emission map's Alpha Channel, usually connected to transparency.

Typically, the alpha channel of the Emission layer is edited with blacks, whites and greys to control the speed and style of the glow / flash. 100% Black means a constant glow. 100% white means the glow will fade in and out pretty fast. And then there's the greys in the middle, and the darker the grey the slower the glow. I'll show some examples of this later.

 

The colour of the Emission layer glow is controlled by the Red, Blue and Green channels, usually referred to as the RGB. We won't need to touch those for this guide.

 

 

Editing the texture of the CAS item

1. Open Sims 4 Studio.
Select 'Create CAS Standalone' under CAS and then click the blue button.

Next, we have to choose our CAS item. I highly recommend choosing a Top to keep our intro to the Emission layer easy. 

There are numerous drop-downs at the top:

 

- SPECIES: Keep as Human.
- GENDER: select Male or Female.
- AGE: For now, choose Adult.
Part Type: Select the CAS category. For now let's pick Clothing Top.
- GAME PACK: Filters the items that come up by Pack. You can set it to All. I'm just going with Base Game for now.

 

I'm going to pick the black T-shirt.
Click 'Next' in the bottom-right corner and save the .package file.

 

2. We are going to Export the T-shirt texture.

When Sims 4 Studio opens the object, it should automatically be on the Studio tab (where the model appears).

- Make sure you are on the Textures tab on the left-hand side. On the box underneath 'Swatch Thumbnail', you'll see a list of Textures. We want the Diffuse - the main texture.
- Select the Diffuse and click Export. Export it as .png. 

 

3. Find the design that you wish to put on your T-shirt. I recommend using a one-colour image, lineart or silhouette.

 

- Make sure you have permissions to use the image for your CC and credit the creator of the asset if you upload the CC anywhere.
- I am using this paw print, which requires attribution but is free to use otherwise. (I'm going to get rid of the heart shape).
- Try to find a .png file. A .jpg silhouette isn't the end of the world, but it might need some cleaning up. Mine was .jpg, but I can show you how to clean it up a bit if you have a .jpg silhouette.

 

 

Preparing the design 

4. Open GIMP. 

- Press CTRL + O to Open up the Diffuse layer (with the T-shirt texture).
- Then press CTRL + O to open up the image you want to put on the T-shirt.

So there's two problems - one, the white background, and two, the heart. To get rid of the heart:

 

- I press the O key to bring up the Colour Picker and I click the black paw-print. This will change your active colour to the exact shade of black of the pawprint.

- I press N to bring up the Pencil tool. 

I make sure the brush type is the 'Hardness 100' brush and then I draw over the heart until all I have is the paw print.

 

5. Now to get rid of the white background.

- I click Shift + O to bring up the 'Select by Colour' tool. 
- I click the white.
- I press Delete and...nothing happens? 

This is because this image has no Alpha Channel, and so no transparency. So let's add one!

Go to the menu toolbar at the top, and then click Layer > Transparency > Add Alpha Channel.

 

Now I've done that, it's let me delete the white and now I only have the paw print - but I want to change the colour of it. 

 

I am going to use the Select by Colour again on the black. This is a very crisp sharp image so I don't need to worry about any stray pixels not getting filled.

 

- Press Shift + B for the Bucket tool.

 

 

 Make sure it is set to 'FG Color Fill' fill type and 'Fill Whole Selection' for Affected Area.

 

Underneath the tools is the Colour Picker. The top left one is the FOREGROUND colour, and the bottom right one is the BACKGROUND colour.

 

Change the FOREGROUND colour to whatever colour you like. I recommend something vibrant!

 

6. Booooo! So I was wrong. There are stray white and black pixels all around it. Let's fix it!

 

- Use Shift + O to bring up the Select by Colour tool, then Select the transparent background. We're going to increase the size of the selection so we can delete the stray pixels.

 

On the menu toolbar, go to Select and then on the drop-down select 'Grow...' . 
- On the little dialog box that pops up, change the number to 2 px (pixels). Then click OK.
- You will see that the selection has increased slightly and is now including the fuzzy edges.
Click Delete, and then press CTRL + Shift + A to deselect.

 

If there is a lot of empty space around your image:

 

- Go to the menu toolbar at the top and click Image
- on the drop-down menu, click Crop to Content and it will crop the image right to the edges of your design. 

 

However, my design is still way too big to work with right now, so: 

 

- Go to the menu toolbar and click Image
- on the dropdown, click Scale Image.

I resized my paw print to a more manageable 500 x 487. Don't touch those little chain link icons, leave them as is so your image resizes in a uniform manner.

 

Make sure the Interpolation is 'None', so that it won't have blurry fuzzy edges when you resize it.

 

SAVE this image! 

 

 

Putting the design on the T-shirt

Open the T-shirt texture in GIMP.

 

- On the Menu toolbar, click Layer, New Layer, leave it as transparent and then click Okay. Usually your pasted-in design is automatically a new layer but we're going careful!

 

Paste in your design and use the Move tool (M key) and Scale tool (Shift + S) to move the image and resize it until you are happy. Try not to put the design too high up on fem-frame tops because the boobs might distort them too much.

 

Save this as both .xcf (or .psd if you're in Photoshop) and also go to File > Export As...and export it as a .png. 

 

8. Go back into Sims 4 Studio. With the Diffuse texture selected, this time IMPORT the T-shirt texture with the design on it.

 

Look at the model and see if the design looks okay. If it isn't, go back to your .xcf file and move and resize the design around until you like it.

 

 

It doesn't look great, but that's fine, because all I'm doing is teaching you how to make stuff glow. 

 

Whilst in Sims 4 Studio, on the Textures tab, make sure you click 'Make Blank' on the Normal, Specular and Shadow maps. I always do this to make sure it doesn't interfere with the Emission glow.

 

SAVE a copy of the .package file.

Now for the Emission layer! *internally crying*

 

 

Creating and importing the Emission Map

Emission maps can sometimes be tricky depending on what CAS part type you're working with, as the size of the Emission map will differ depending on which CAS part type you are working on.

 

It appears, both from my digging and some of the information from CMar's Emission map guide, the size of the Emission Layer appears to be the same as an object's Normal layer.

 

Typical emission sizes for certain parts are:

 

- Top, Full Body and Bottom: 1024 x 1024
- Hat: 512 x 256
- Shoes: 1024 x 512
- Eyes: 1024 x 2048
- Ring: 1024 x 2048 

 

An easy-ish way to be sure what size you need is to export a .package file from Sims 4 Studio of an object of your desired type that has an Emission map. To find out what emission size I needed for a Hat, I had to export a .package of the Logitech headset from the Base Game that had an in-use Emission map. Then I exported the Emission map and looked at the dimensions of it. It turned out to be 512 x 256. 
You can also do this by downloading CC of your desired Part type that has an in-use Emission map and exporting it.

 

Typically, a Top's Emission map is 1024 x 1024. I edited a Ring to make some custom content and the Emission layer was 1024 x 2048.

 

So, for the Emission Map, let's open up the .xcf file. Gimp's .xcf file it is native file type and preserves all your layers separately.

 

9. Delete every layer you have EXCEPT for the design.

 

We need to make this 1024 x 1024, but carefully, so the design ends up in the correct position.

 

- Change the 2048 number to 1024. You'll notice the long box on the right change.
- Drag the bottom part of the right-hand box UP all the way, so it's in the middle of the white box.
- Make sure the little chain link is UNLINKED.

 

Once it's 1024 x 1024 and you've moved the texture all the way up on this box as far as it can go (so it's in the middle of the white box) and click OK.

 

After this, go to Layers on the Menu toolbar and then on the drop-down select 'Layer to Image Size'. 

 

Huzzah! Now to edit the Alpha Channel. 

 

In the bottom-right Layers tab, navigate to the above-circled Channels tab. 

- Once this is done, highlight the Alpha channel like above.

- Go to the Layers menu, then to Masks > Add Layer Masks. 
- Instead of Selection, choose 'Black (Full Transparency)'.

 

IMPORTANT: SAVE your Emission map texture before you do the next step.
If the Emission layer goes wrong or accidentally has something on it you want to delete, it's a bit easier fixing a .png, so save it as .png now as a backup before we edit the Alpha Channel.

 

When you click OK, the image will disappear. That's fine.

 

You can add different shades of greyscale on the Alpha channel, but I will show you how that affects the flash / fade-out glow later.

 

Once you've done this, go to File > Export As... and then export as a .dds file type.

 

Make sure it's set to DXT5 and Generate Mipmaps is selected.

 

10. Back in Sims 4 Studio, with your .package file open:
- On the Textures tab, select the Emission Map and Import your .dds file.

 

Through Cmar's guide, which although 7 years old is one of the more informative and clear guides on Emission map shenanigans - You can actually preview your Emission map a bit using CAStools.

 

- Open your .package file in CASTools.
- On the top set of tabs, click Previewer.
- All texture maps except the Bumpmap should be displayed already, but if not, make sure the Diffuse and Glowmap are ticked.

 

If you can't tell if you can see the glow or not, click the Glowmap on and off and you can then check that the glow is coming up in the way you expect it to!

 

It is coming up correctly here, but I hit a snag with this particular design and shirt. I'll explain it just in case you bang into the same issue.

 

Now, this is only a tutorial on the Emission map, but for clarity's sake in terms of whether or not the Emission covered up the entire desig , I wanted to make sure the pawprint wasn't going to get warped by the breasts. so I moved it quite far down. Then in-game this happened:

 

If you notice, only half the design is coming up with the glow, cut straight across.

 

I could NOT for the life of me work out what the problem was.
Shadow, Specular and Normal maps were blanked. 
The .dds was the correct size, with mipmaps, and matched up perfectly with the Diffuse texture. 
So what the HELL was the issue? I decided to go into CAS Tools and dig around.

 

I opened up the CASTools previewer and I noticed you could make certain parts of the model invisible - then I found the culprit.

 

 I hide EVERY mesh on the default model and I noticed that the cutoff on the Top, was the same glow cut-off in-game.

 

What's happened is that I've put the design too far down - so the bottom half of the pawprint is in the 'Bottom' section on the mesh.

 

 

I layered the texture on top of the UV coloured section layout, and you can see the texture crosses into Bottom a bit, and I guess the way the mesh warps the texture makes the bottom half of the pawprint cross into the bottom when it's applied to the mesh. At least, that's what I gather.

 

(Trust me to run into an issue like this during a bloody tutorial. Well it's good I did because I could have given you a possible solution to a possible issue you might run into.)

 

So, I moved the pawprint design higher up (and made a new Emission map with the pawprint in that position)

 

And now look! IT WORKS!

 

Another possible thing that you could do is - remember when we did the 'Grow...' on the Selection earlier to get rid of stray pixels?
You could have the edges of the design DON'T glow, but the inside does by doing this. (This looks quite nice on eyes.)

 

- On the .png version of your Emission map, before editing the Alpha Channel, select the transparency around the design.
- Go to Select on the top menu and then to Grow....
- Choose any number from 1-3 px, and then click Okay. 
- Then press Delete to get rid of the bits that are now within the selection boundary.

 

Then, edit the Alpha Channel using Layer > Masks > Add Layer Masks > Black (Full transparency) whilst the Alpha Channel is selected, as explained in this tutorial, and then test in CASTools.

 

There we go!

 

So let's look at controlling the speed of the fading glows, shall we?

 

 

Controlling the fade in-out speed of the glow using the Alpha Channel

As I explained earlier, the fade in-out of the glow is controlled by the monochrome shade of the Alpha Channel.

 

100% black, like we did, is a persistent glow that doesn't fade.
100% white, and the fade in-out is very quick.

 

The darker the shade of the Alpha Channel, the slower the fade-in-and-out of the glow. The below .gifs show you some examples:

 

 

If you don't edit the Alpha Channel at all, it will end up white on all the texture parts, which causes the quick flashing in-game, which is an issue you'll likely run into whilst doing anything with the Emission map.

 

 

I cannot guarantee that this method will work EVERY time you have a non-1024 x 1024 or non 1024 x 2048 emission map, but this is how I made my Emission map for the hat-based project given its 512 x 256 sizing. It wasn't as easy as making a 1024 x 1024 from a 1024 x 2048.

The Emission layer for the hat is 512 x 256, so that's the size my Emission layer needs to be.
That's a bit more difficult than it being an easy size like 1024 x 2048. 

 

I downloaded the adult female coloured section template from this Sims 4 Studio forum post (Download from the linked .zip file).

 

I opened it on GIMP, and then imported my texture for that object. 

 

I then go to Image menu at the top, and then click the 'Crop to Selection' option on the menu. This crops the whole image to fit the square / rectangle selected.

 

I quickly go into Image > Scale Image to check it's exactly 512 x 256.

 

Then I delete the coloured sections template, and I get rid of ALL the base texture (the black) leaving ONLY the glow texture, since the Black is part of the Diffuse, not part of the glow.

 

Now I have to repeat the Emission layer steps from earlier in the tutorial, making the Alpha channel completely black and then saving as .dds. After exporting the 512 x 256 .dds layer...

 

Huzzah!

 

 

Possible Issues, Possible Causes + Possible Fixes

•  If your CC's glow is flashing quickly, then you didn't change the colour of the Alpha Channel. Go back to the step about editing the Alpha Channel.
  
  
• If your CC's glow is coming up wrongly, or not at all, you either made the error I did where there's a crossover between parts on the original CC, you didn't select 'Generate Mipmaps' when saving the .dds file, or you did not make the Emission map the correct dimensions (depending on what part you're editing, might be some trial and error to find the right size)

Have fun!