Welcome on this Normal map Tutorial a Correct and Easy way to do it.
This tutorial will explain what you will have to do to make a correct Normal Map for the Source Engine.
For this tutorial you will need:
For this Tutorial I will use my PP-2000 Texture
Firs I will show you how many do it and what is actually WRONG!
Mostly the Diffuse Map is used to Generate this Normal Map like shown above.
What happens here is that the Normal Map Plugin takes the diffuse White and Black as Height and Depth to generate the Normal.
If I would use this method on my PP-2000 it would look something like this in game:
The normal created here is made from the diffuse the base will look all like stone and the parts that should be engraved or extruded will have a totally wrong effect.
To make a proper normal map you first need to make a Height Map (Bump Map). Starting off with the neutral gray "RGB: #505050. Than painting all the objects that you want to be extruded White and those you want engraved Black.
You don't have to start with the gray surface you can also make the bump maps in several layers with just only black and white and normal mapping them separated with overlaying the final result on top of each other.
Here's a small example of a height map(bump map):
It are just simple stripes from black to white in different steps. Applying the Normal Map Filter it will come out like this:
Though because we are working with the Source Engine the Green Channel or Y-Channel should be inverted so it fits the light direction of source. "Note: This is not always the case"
Its not hard to flip the Green-Channel or Y-Channel. You can do this by going to your Channel Tab or in the nvidia filter by checking an option:
On the left you see the normal map filter, to change it you only need to check Invert Y or you could go to your channels tab (In default workspace next to the Layers Tab) than select the green channel and press crtl+I (Invert)
If we would render this Normal on a plane surface it will look something like this:
Now if we would make the height map for the PP-2000 it would look something like this:
The grip, text and hole's are filled with black, because they need to be engraved down, but like the screws and the front pattern they should come out so they require to be white. Do note not everything need to be bumped, only the things that aren't modelled like grip, text, patterns, etc...
If we would now run this Height map trough the Normal Map Filter this would be the result:
The normal applied onto the model it would give us this effect:
With the right normal map applied the text is correct engraved and the metal surface is smooth as it should be.
This is quick tutorial of how to make a Correct Normal Map from a simple Height Map.
I hope that you won't never use Diffuse Normal Mapping again and make proper Normal Maps for your releases.
But to memorize it a bit better:
