Making the texture glow in-game is a simple. I'd suggest using photoshop or a free sofware called paint.net (It's referred to as "PDN"). I do not use photoshop because i'm a cheap-skate, so i'm going to be explaining the PDN side to doing this. PDN will do the job just right though. :)











To start off, you want to select the parts of the image that you would like to glow. You want to do CTRL+C to copy it, add a new layer on the bottom right and do CTRL+V to paste what you just copied. (If the entire texture needs to glow, skip to "Setting Up The VMT").



























Now what you need to do once you've created your layer with everything you want to be have glow, you want to select your main layer (The one that does not glow) and then click on the little wrench icon on the bottom left right of the "layers" tab.




Inside the little menu that pops up, you want to change the opacity all the way down to 1.
This should make it practically invisible with the glow part clear as day.
















You should always want to save it as a normal old PDN file just in case you mess up somewhere and need to go back to fix it. If you don't, then i'm sorry but you'll have to either deal with the bug or start over. After you have saved the PDN file, you want to save it as a PNG file with a name of your choice. Now it is time for VTFedit.

Alright, so you saved the image as a PNG on your desktop. (It should be flattened first). Good; let's open up vtf edit. Prepare for some reading:

In vtf edit, go to file, import, and then select your png image. Depending on how big your image is, (It should be nothing more than 512x512 or 1080x1080), it might take a little while to pop up on the screen. Once it's opened, for the flags on the left, check SRGB. Now you want to save it with a name of your choice in wherever your materials folder is in the game directory. Go to options > create vmt. The little menu should pop up. Go to the options tab. For the shader, if it is a normal texture that will go onto a normal surface in hammer, leave it on "LightMappedGeneric". If this texture is for a model, always set it to "VertexlitGeneric". Select your surfaces you want, and then you want to make sure "Translucent" is unchecked. Click on create, and then save. Now you want to go to where you just saved that vmt and then open it with notepad or notepad++. If it is for a model, then add " "model" 1". under everything, add " "$selfillum" 1".

FREAKING REMEMBER TO SAVE.

You are now done; congrats on your success. Now open up hammer and pop in your texture or model and see how that baby looks in-game.




In this image I used an env_lightglow for that sexy glow detail. Without it, it will glow in the dark regardless. :)