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Editing Surface Normals

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Ryokukitsune give you an explanation of normals and normal maps

Well if you’ve started working in radiant by now you’ve noticed that anything you build with brushes is very sharp and angular where if you work with terrain its very soft smooth and organic.

The difference between these two types of surfaces is the surface normal. Like normal maps, surface normals are just another way of creating the illusion of surface texture, basically how it receives light.

A Normal Map is how a surface generates shadows; a surface normal is how we fake curvature. I know it sounds like I just reverse what I originally said but bear with me. You have to have a surface normal to use a normal map, a normal map manipulates the surface normal to create texture. So how does terrain fake curvature and solid brushes do not?

Well the answer is a normal texturing however it’s not as simple as that. If you try to throw a texture with a Normal map on a surface you’ve tried to make look smooth and curved you’ve noticed that you still get all the sharp edges produced by the corners of the brushes. If you’re reading this then its something that you want to make go away.

First off, what is a surface normal? A surface normal is how geometry appears to have a surface. All that geometry is really a series of points in space. They have no volume and no actual surface so they can’t be solid based on that information alone.

To have a surface you need to know a few things, first where is the surface? Well a surface is defined by the location of the points, a point, known as a vertex or plural vertices. You need a minimum of 3 vertices to define a triangle which is geometry or a polygon.

How do you have volume? Well volume is created when you have a closed shape, meaning that all polygons are connected and there are no holes. So anything inside the points in space would be considered its volume.

So why is a Terrain patch one sided and how does that work? Well a terrain patch is just a surface; it’s not supposed to have volume. How it works brings us to the actual Surface Normal

Without getting into the painful math of it, a surface normal is the direction of any given piece of geometry. Relatively speaking it means up or in the case of solids; out. This is why when your camera is inside a large brush you don’t see it.

So how do you change surface normals, its actually very easy. Radiant is much simpler than professional programs like Maya or 3ds Max so the guys at IW broke it down into a matter of texturing but you won’t find your surface normals in the texture pallet. You have to change the surface mode.

There are 3 modes you can toggle threw: Textured, Light map, Surface Normals. To toggle threw them you press Shift-L on your keyboard.

Textured mode is obvious, you start off in it.
In this mode you can add and adjust surface textures the information you see in game in all modes you have the ability to change the tiling and angle of the materials applied to brushes

Light map mode is used to fix problems you have with light maps, like with textures when you stretch them out really far they don’t look rite if you stretch out your geometry then you end up with light map problems, this is where you fix it simply by adjusting the tiling of the light map grid, the checker pattern material.

Finally, Surface Normal Mode.

There are 3 textures in this mode: Smoothing_Hard, Smoothing_Soft, Smoothing_Smooth_Other. With exception to the last they are pretty self explanatory. Hard gives you corners and edges smooth is… well smooth. I’m not exactly sure what the smooth other does but it doesn’t work like the swatch seems to suggest. If you know what it does PM a mod and have them edit this tutorial.

To change how surface normals are used its pretty easy, just select a face and apply a different normal texture. I personally think they dumbed down the operation a little to far but what ever works.You can’t preview the surface normals in Radiant but I assure you they work

Now there are some problems with messing with surface normals.

First you cant use Alpha Blending with surface normals since you aren’t really working with textures. You may be able to make a believable cylinder out of brushes but if you make a beveled cube edges will really pop out. Since building in radiant is like building with Legos each shape has its own surface normals and they aren’t directly connected which is the problem.

You could use surface patches to create complex forms but it leads to texturing problems and it gets to be a bigger and bigger mess the more you try and fix it.

To cut it off here, this is how you edit surface normals but use them wisely…

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