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At the present day, almost in all 3d editors two kinds of textures are used: bitmap texture (usual raster image) and procedural textures - these are computer generated images created using an algorithm intended to create a representation of natural elements such as wood, marble, granite, metal, stone, and others. Such textures can be of two types: two-dimensional (plain) and three-dimensional (volumetric). About this textures' type we'll talk a little bit later in the article "Animation of Procedural Textures".
Texture (texture map) is a raster image (bitmap) applied to a surface, the picture of which is used for making relief, transparency, reflection, specks, etc. As textures can be used either graphic formats ((jpeg, png, tiff, tga, exr and so on) or video formats (avi, mov). Also don't forget about procedural textures, that also can be used as textures. When we use raster images in the capacity of textures, the following functions can be added to them in any 3d editor: smoothing, blur, brightness, contrast ... . The most interesting thing for users - parameters of texture adjustments, that directly have an effect on a material, changing its properties.
Here are parameters that are present in Blender (in other editors too):
1) Color - causes the texture to affect basic color of the material.
2) Nor (Bump, Relief) - causes the texture to affect the rendered normal. It adds the effect of a relief without object's transformation.
3) Csp - causes the texture to affect the specularity color.
4) Cmir - causes the texture to affect the mirror color.
5) Ref - causes the texture to affect the value of the material's refelectivity.
6) Spec - causes the texture to affect the value of specularity (specks).
7) Amb - causes the texture to affect the value of ambient.
8) Hard - causes the texture to affect the hardness value.
9) RayMir - causes the texture to affect the ray-mirror value.
10) Alpha - causes the texture to affect the alpha value and it is used for disguise of some object's parts on the basis of a definite texture's color or image's alpha-channel.
11) Emit - causes the texture to affect the emit value.
12) Disp - let the texture displace the surface. This function is similar to Bump. The texture deforms the object. For correct work any mesh you work with should be well subdivided.
As a rule, all afore-mentioned settings work well with usual color raster images, using information about pixels' brightness, that is why in most cases there is no need in additional texture maps when using seamless textures from the assistcg.com website. However, such a necessity appears when some effect should be created, for example, bulging and dislodged stones on a roadway. For creation of such a texture (Bump map) a basic color texture is used. In any raster editor, for example in Gimp, a basic texture should be decolorized, having indicated the basis for hues of grey color (it is better to choose midtones). The next step that is necessary to carry out is to lighten and darken some separate fragments of your image. Using the same method we also can make additional maps to all afore-mentioned settings.
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