- Blender 2.5 Materials and Textures Cookbook
- Colin Litster
- 877字
- 2025-03-31 05:24:23
We discovered early in the first chapter that man-made materials will often closely resemble their natural surface attributes. Slate is a natural material that is used in many building projects. Its tendency to shear into natural slices makes it an ideal candidate for roofing. However, in its man-made form it is much more regularly shaped and graded to give a nice repeating pattern on a roof surface. That doesn't mean that there is no irregularity in either the edges or surface of manufactured slate tiles. In fact, architects often use this irregularity to add character and drama to a roof.
Repeat patterns in a 3D suite like Blender can be extremely difficult to control. If repeats become too obvious, particularly when surface and edges are supposed to be random, it can ruin the illusion. Fortunately, we will be employing Blender controls to add randomness to a repeated image representing the tiled pattern of the roof.
Of course, slates like any building material need to be fixed to a roof. This is usually achieved with nails. After time, these metal joiners will age and either rust or channel water to add streaks and rust lines across the slate, often emphasizing the slope of the roof. All these secondary events will add character and dimension to a material simulation. However, such a material need not be complex to achieve a believable and stimulating result.
The preparation for this recipe could not be simpler. The modeling required to produce the mesh roof is no more than a simple plane created at the origin and rotated in its Y axis to 30°. The plane can be at the default size of one blender unit and should have no more than four vertices. That's just about the simplest model you can have in a 3D graphics program.
Position the camera so that you have a reasonably close-up view as shown in the following image:
The default lights, as suggested in Chapter 4, Setting a default scene for materials creation, will be fine for this simulation. But, you are welcome to place lights as you wish. Please bear in mind that a slate roof tends to be quite a dark material. So, if test renders appear too dark, raise the light energy until a reasonable render can be produced. You can also turn off Raytrace render and Ambient Occlusion, if it has been previously set, as they are not required for this material. This will save considerable time in rendering test images.
Save your blendfile as slate-roof-01.blend.
You will also need to either create or download a small tileable image to represent the pattern of the slate roof. Instructions are given on how to create it within the recipe but a downloadable version is available from the Packtpub website.
We need to create an image of the smallest repeatable pattern of our slates. This can act both as a bump map and also to mask and apply color variation to the material.
The image is very simple and is based on the shape and dimension of a standard rectangular slate. You will see later how the shape can be changed to represent other slate patterns.
This was created in GIMP, although any reasonable paint package could be used. Here are the steps to aid you in creating one yourself:
- Create a new image with size
260x420pixels. I will show later how you can scale an image to give better proportions for more efficient use within Blender.
- Either place guides or create a grid to sub-divide the rectangle into four sections.
- In the top half of the rectangle, create a blend fill from black at the top to white at the middle. Do the same for the bottom half of the rectangle.
- Create a new layer and draw a black line, of three pixels' width, from the middle of the top rectangle section to divide the top rectangle into two.
- Draw black lines of the same thickness on each side of the whole rectangle. If you used a grid, you should find that one of these verticals is two pixels' width and the other one. Obviously, when this image is tiled, the black lines will all appear as equal in thickness.
- Finally, create another blend fill from the bottom of each rectangle from black to white upwards about ten pixels.
- Save your completed image as
slate-tile.pngto your Blender textures directory.
If you want to skip these steps you can download a pre-created one from the Packtpub website.
The image that you want to tile must be carefully designed to hide any seams that might appear when repeated. Most of the major paint packages, such as Photoshop and GIMP, have tools to aid you in that process. However, manual drawing, or editing of an image, will almost always be necessary to create accurate tileable images. Even tiny variations between seams will show up if repeated enough times across a surface. Fortunately, there are techniques available in Blender that will help mask these repeat image shortcomings.