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How to blend terrain

To make your terrain more interesting, you will want to know how to blend. Blending allows you to fade two or more differently textures terrain into one. This could be used to put snow on mountain tops, make paths in the grass, or any other number of things.

*edit: after a couple requests, I went back and created a sample map and bsp for download. While this sample map contains the same textures and components, I added hills to this o­ne in order to show it off more. blend.zip

1. To keep things simple, let start with a simple square brush that we will be using for our ground. I made a square brush that was 384 x 384 units. I just wanted something that was larger enough for my test player to run around o­n and look at out final terrain. The height was left at default since it will not be important o­nce we turn this brush into a terrain patch mesh.

2. Let's also texture this brush with something dark so when we later texture it with snow, you will be able to clearly see the blending in action. Selecting the correct texture is a very important step. It must be a solid texture which is denoted with a @ symbol in the name of the texture and is not displayed with a white border in the texture preview window.
I have chosen to use belgium/ground/rock@snowycreekbed from the collection of ground textures in the belgium set. This texture has the @ symbol and does not have a white line around the texture.

3. Move up to the top menu and open Patch > Simple Terrain Mesh...
This option will allow you to create a mesh of polygons that divide up your brush so you can give it terrain-like characteristics.

*note: For terrain meshes to be shaped into hills and mountains, you need points that can be moved around. If you o­nly have four points, which would be the case if we did not divide up the terrain, you would o­nly be able to make a slanted brush. But, if you had some points in the middle that could be moved up or down, then you could start making your hills and valleys. The more points you have to work with, the more detail you can put into your terrain. However, the drawback to having too many points is that the game-play could suffer from lag. Extra points means more work for the game engine and you have to find that happy medium between a great looking terrain and a easily playable map. That takes experience which are are developing now.

4. When you open that menu option, a small box will pop up asking you what terrain density you would like to create. This is the number of divisions that will take place in the X and Y axis (forward to back, left to right). With terrain, we are not concerned with dividing the terrain o­n the Z axis since we o­nly need a 2 dimensional area to view. I suggest just dividing your map up using a width and height of 3. This is o­nly a test and we want to keep things simple.

*note: It is possible to divide terrain o­n the Z axis. You will notice the pop-up window asks for width and height. This works for which ever view window you are working in. Since we are viewing from the Z axis denoted by the small Z in the middle of our work area, width and height will effect the X and Y axis. However, if we switch our view point to another axis like the X or Y, the width and height will effect the other two axis. This is great if you want to create a wall of terrain like o­n the side of a mountain or even in a trench.

5. We must now copy this brush for the texture that we will be blending over our rock texture. Hit the space bar o­nly o­nce to create a copy and then move this brush to a clear area so we can work o­n it without accidentally effecting anything else around it.

. Let's select a contrasting texture to blend with our dark rock texture. I have chosen to use a snow texture. Again, selecting the correct texture is a very important step. This time we want to select a texture that has an alpha channel. An alpha channel mean that the texture has transparent qualities that also makes it a non-solid. If we used this texture as out main texture for the terrain, our player would just fall through it. However, with the solid texture used first, we will ensure that our player will remain o­n top of the terrain when we are finished.
I have chosen to go with the texture belgium/ground/snow_1024lightfill. Note that there is no @ symbol in the name, but there is a white border around the texture in the texture preview window.

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7. It's time to start editing our texture for blending. To do this, hit the y key o­n the keyboard to bring up the Advanced Patch Editing Option (aka, terrain editor). I will leave the default radius and amplitude for now. I will select the option to Flatten, deselect the option to Allow soft select o­n un-highlighted patches so as not to accidentally effect any unselected terrain, and I will select the option for Alpha.

. Now we can "paint" o­n our "transparent" area to the non-solid texture. When you move your cursor in the D window, you will notice it looks like a group of rings now. These rings consist of the inner radius and outer radius. The inner radius has a direct effect o­n the terrain texture with the outer radius works like a gradient where is gradually effects less of the terrain texture from the inner radius outward. If that sounds confusing, don't worry. It will all make sense o­nce you start playing around with it.
From within the 3D window, place the rings in the center of o­ne edge of the snowy terrain, hold down the alt key + left mouse button. Begin to draw a straight line through your terrain as if you were creating a path. as you move your mouse back and forth, more and more of the texture will gradually be effected. Continue to move it until you see a solid gray line down your path. This solid area will be complete transparent in the game while the surrounds snow will be completely visible.

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. o­nce you are happy with your snowy terrain, hit the y key again to close the editor.

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10. We must now move the snowy terrain back to where it came from. This would be the exact same position as the dark, solid rock. These two terrains need to be sharing the same space so the game doesn't know they are separate terrains. While your snowy, non-solid texture is still selected, you should be able to see the blended terrain as it will be displayed in the game. o­nce you deselect your brushes, you will no longer be able to see this snow even though it is still there.

. Finally, I have created a test room around my terrain and placed a player spawn point inside. This way I can compile and test the map to see how it all worked out.

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