A Short and Easy Tutorial on Alpha and Clip Mapping
Introduction
Alpha and Clip maps are both very useful when creating complex textures in Lightwave. Surprisingly, the book doesn't mention either of them.
This tutorial will give you basic examples of how to use both types of maps for your Lightwave scene. First let's talk about alpha maps. Alpha
maps use black and white colors as information telling Lightwave how to render certain elements. For example, when an alpha map is placed on top of
two color maps (in a layered texture) only specific parts of the color maps will show up. This is dependant on what areas are black and white on the
alpha map. Basically, anything black will show the bottom layer, and anything white will show the upper layer. Here's a good example from 3dTotal.com:
Alpha Maps:
Creating a Simple one of our own :
Let's create a very simple wall that will can texture with 3 maps. 2 color maps and one alpha map.
Model a simple wall
1) create a simple model of a large wall about 8m X 6m
.
2) give the wall a surface name
-Now here you would create any UV maps that you would want to use for your textures
(which is highly recommended when working with multiple walls to ensure that textures at the corners meet together realistically)
That completes the modeller end of things, now find any textures online that you are going to want to use for your wall and have them ready.
Here are the textures I'm using:
3) Load the object into Layout and open up the image editor to load all the image maps that you are going to use:
4) open up surface editor and select the surface you named earlier for wall.
5) click the T button next to Color to add a color map:
6) Select the first color map for your wall (in my case stone.jpg) and give it a Planar projection over the X axis.
(or select your UV map if you made one)
7) hit the Auto resize button (if you have no UV) to fill the wall
8) Now we want to rotate the image 180 degrees so the dirt is coming up from the floor rather than down from the cieling.
to do this, Select the Rotation tab and enter a value of 180 in the "p" text box. The texture should rotate.
Next Repeat steps 5 through 8 but on the Bump channel and add your corresponding bump map to the stone wall. (in my case stone_bump.jpg)
9) Ok, Now go back to the Color channel's texture editor and add a new layer, select Image map as the option
10) Select the next wall image that you would like to use and set it to a Planar project on the X axis once again (rocky.jpg) except
this time don't rotate it. Enter any settings to your pleasing for the size, In my case I kept the size at the default 1 x 1. This texture is going
to be the rocky texture on top of the stone, so its probably not a good idea to stretch it out too much. or the rocks will look disproportioned.
Do the same steps once again for the Bump channel, but use a correct bump map and scale it exactly the same is the map you used in the color channel.
Next we will load our alpha map.
11) Under the Color texture editor again, add a new layer > image map. Load up the Alpha map that you picked to use and set the projection to planar along the x axis just like the other two layers. Size the map however you wish, but keep in mind that in the final render, the black areas of the Alpha map will show the bottom layer, and the white areas will show the next layer above that. In my case first hit the auto size button for the X scale, but changed the Y scale to 3 and the Z scale to 5.
12) Next, and most importantly, under Blending Mode at the top be sure to set the selection to Alpha, or else you will have a funny looking black and white splotchy wall. Your settings should look similiar to the screenshot below:
Once again, Repeat these steps by adding an Alpha Map to the bump channel as well, so that the proper bump settings are shown correctly for each image map that are shown in the color channel.
Finally, render your wall making sure you have Anti-Aliasing on, and you should get something like the screenshot below:
There you have it, a very fast example of using alpha mapping to add multiple image maps to a texture.
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Clip Mapping (summarized tutorial)
Let's create a banner similar to one shown below:
Go out and find an image online of a poster or banner that you would like to use for your model.
Here is what I came up with, its a banner with Roman symbol:
Save your image somewhere handy for use later on.
Next we need to open up an image editing program such as photoshop in order to create our clip map.
1) Using your program (I use Photoshop) draw an image similar to the one below:
This is done by drawing an outline freehand with a pencil tool and then using the paintbucket tool to fill the outer edge black.
2) The edges of the clip map must be sharp and can have no AntiAliasing, so in order to do that click Image -> Adjust -> Levels to bring up the box below:
Enter the settings shown, hit ok, the save your picture as a .jpg somewhere where you can find it easily.
Now, open up modeller and create the banner:
1) Select the box tool and then bring up the numeric properties dialog box and enter the settings shown in the picture. Give the object a surface name then save the box and exit modeller.
2) open up the box that you just created in Layout. Adjust the camera so that the soon to be banner is in clear view.
3) open up the Surface editor for the box, select the surface you named it.
4) select the Texture button next to color to bring up the the Texture Editor.
5) Click the image tab and select Load and navigate to the banner picture you got off the Web earlier.
6) set the projection to planar on the proper axis (in my case Y). Select the AutoSize button to fit the picture properly on the box.
Now to add the clip map:
7) click the objects button at the bottom of the screen and set box that you mad as the "Current Item"
8) click the Properties button that is to the right of the Objects button. This will bring up the Object properties dialog box.
9) click the Render tab, and you should see an option for "Clip Map"
10) next to "Clip Map" is a "T" texture button. Click it to bring up the Clip map Texture Editor.
11) Setup the clip map using these settings (be sure that blending mode is set to Additive!):
12) close the clip map texture editor, set up your camera and do a render. It should turn out something like this:
Later you can add a displacement map to give it some cloth like feel, or an alpha map for dirt.
Thanks for following along!