An important reminder about normal maps

[Cool_Z 1,547]

Hi guys.

 

As you know, adding a normal map can really help adding detail to a model without using more polygons.

 

There are lots of free and paying progs around to help you creating rormal maps for your models, or help you converting a black/white map into a true RGB map.

There is ONE point that I hope most modelers are aware of, and if they're not I hope they'll now take this into account.

 

You HAVE to invert the red channel of the normal you make or the generated shadows will be wrong.

Here are some pictures to show you what's happening (thanks to GULA for them  )

First here's a normal map: the right part of it has had its red channel inverted

 

Let's look at it applied to some building ingame :

 

The light is coming from the left. Now look at the left building and you'll notice something weird. Yes, the shadows are left/right inverted. The dark parts are on the left and light ones on the right. This is because CSL does not use the standard normal map setup.

Then, in order to get the right results (like on the right building) you MUST invert the red channel of your normal. Some normal map softwares offer the option (NormalMap online does) some others don't, for those you'll have to manually do it in photoshop.

 

(if you're not sure of how your software handles the red channel, do some test like the one above, but it looks like most industry standard software will request this inversion).

 

It looks like most workshop assets use bad normal map settings, and I'm not even 100% sure all vanilla buildings are correctly made  ... but now that you've read this, you've got no excuse for doing it wrong anymore.

 

 

Thanks for your attention, enjoy the game, enjoy building stuff.

  Edited August 17, 2015 by Cool_Z  

[GC_Vos 714]

Thanks for this post Cool_Z! The normals in this game were confusing me, this really helps clarify...

[Drosovila 86]

God dammit thats why my normals never looked quite right. All I had to do was invert the y-axis and it looks so much better. I always thought it was because of mirrored or rotated UV coordinates....

[Mr_Maison 2,426]

I knew I wasn't crazy either. I actually inverted one of my normal maps but thought the issue was my fault as I'm new to making normals

[merc187 46]

Thank you for these tips!  I wish we could have some of you experienced guys make one of these "Advice & Tutorials" at how to make better assets once a week!  Thanks again for the tips and will be excited to see if this will affect any of my previous models and make the shadowing corrected (or maybe I did it right already, didn't notice this level of detail when modeling them).

[mntoes 271]

Could someone please explain how to do this in the Gimp for me I am having problems with this at the moment.

[pauliaxz 195]

just mirror your diffuse (or pre-normal ready) texture -> create the normal texture -> mirror back

[Cool_Z 1,547]

6 minutes ago, pauliaxz said:

just mirror your diffuse (or pre-normal ready) texture -> create the normal texture -> mirror back

Yep, the red chanel is for left/right so mirroring the bump map before turning it into a normal and mirroring the result should give the same result.

BTW creating a normal from a diffuse is not the best way to do so (because you'll get a very irregular normal which will result in a very uneven surface.).

[pauliaxz 195]

Yes, so that's why I said pre-normal ready texture in the brackets. In my case it is basically a bit overhauled diffuse texture.

[Lee Towers 179]

3 hours ago, mntoes said:

Could someone please explain how to do this in the Gimp for me I am having problems with this at the moment.

If you've already made a normal map without mirroring your textures beforehand (like I did the first time), you can do the following:

1. Colors > Components > Decompose

2. Choose colour model RGBA, click OK

3. A decomposed image will open with red, green, blue and alpha layers.

4. Activate the red layer and invert the colours (Colors > Invert)

5. Colors > Components > Compose

6. Again, colour model RGBA > OK

7. Save the image as your new normal map.

Don't use this as your normal (heh...) method, it's merely a way to fix it afterwards ^^

[mntoes 271]

Thank you all for your advice.

[Lost Gecko 481]

@mntoes if you have the normal map plugin installed in Gimp (I don't remember the exact name) you can simply check the 'invert x' box in the normal map window to make it right

[mntoes 271]

Thanks @ lost_gecko I'll look out for that . @Lee Towers works great!

Apologies if slightly off subject but I want to ask about this strange effect in-game on my textures . The model looks reasonable in all lighting apart from briefly from one angle and at one particular light level.. As you can see from the picture the front of the house looks kind off dark and "ugly" (see front left) . The bricks on the side look ok by contrast. Is this usual or has it anything to do with my maps?  Wrong settings? I have a normal map applied to the whole model, an illumination map and a specular map applied to the roof only. Oh and of course a diffuse map. I am trying with this first model to learn about all the maps before I move on to other models, so I want to learn from my mistakes first. (Colour map next)

 

[Darf 1,439]

IMO the front looks about right with it's normal map. It looks much more detailed than the side map. Problem is, C:S only shows the normal map under certain angles of sunlight.

[mntoes 271]

Ah, thank you. that explains it. That is why the map is not showing on parts of the building I guess (not showing on right side of chimney). Is it also true that this effect appears to look worse on darker textures and just as you say a limit of the game?

[boformer 3,169]

3 hours ago, Darf said:

IMO the front looks about right with it's normal map. It looks much more detailed than the side map. Problem is, C:S only shows the normal map under certain angles of sunlight.

That's how a normal map works. If you want to show it permanently, bake it into the diffuse texture.

In case of the bricks, you can easily generate a higher-quality normal map from a custom made height map.

[Darf 1,439]

1 minute ago, boformer said:

That's how a normal map works. If you want to show it permanently, bake it into the diffuse texture.

In case of the bricks, you can easily generate a higher-quality normal map from a custom made height map.

Not really, the effect is different under different angles, but it shouldn't disappear completely like in C:S. Just look at common unity renderers like Sketchfab.