One of the main problems with the creation of bitmap based materials is getting them to look as though they repeat or tile seamlessly across a rendered surface. This tutorial explains the various ways by which this can be achieved.
By way of an illustration of the problem, look at the two bitmap tiles illustrated on the right. They are both 100px by 100px. They are both JPEGs and superficially they both look similar. However, when used as a material, one of them displays obvious seams while the other doesn't. The bluewave1.jpg image was created simply by scribbling with the Airbrush Tool in Photoshop. The bluewave2.jpg image has been tweaked so that it will tile seamlessly. The rendered result of each of these two images are illustrated below. The material based on the bluewave1.jpg image is shown on the left and the material based on the bluewave2.jpg material is shown on the right. The bluewave1 material displays obvious vertical seams. In this case, the horizontal seams aren't too obvious but that's more a case of luck than judgement. What we need is a sure fire method of creating a material that can be tiled without showing any seams.
|bluewave1 material exhibiting "seams"||bluewave2 material tiling "seamlessly"|
So, how can an image be tweaked to avoid such seams? At the heart of this technique lies the Photoshop Offset filter. You may have been working with Photoshop for some time and never come across this filter but this is exactly the purpose for which it was designed. Let's first have a look at how bluewave2 was created.
The sequence above illustrates just one strategy for creating seamless tiles. Although in every case, the Offset Filter should be used, there are lots of different ways you might go about building up the texture. For example, one of the simplest methods is illustrated below.
|1. Make a random pattern of splodges but keep away from the edges of the image.||2. Use the Offset Filter to offset half the bitmap height and width and Wrap Around.||3. Simply fill in the gaps with more splodges and Hey Presto! you have a seamless tile.|
If this simple 3 step process is repeated a number of times, you can create beautiful deep seamless textures. After 3 or 4 more iterations using different colours, the tile above finished up as the scrub.jpg file shown on the right. The result of and AutoCAD render using our Garden.dwg file is shown below.
To get some really good results, you need to experiment. Try using different Photoshop filters, consider using Layers to build up your textures. The textures below are the result of a few minutes experimentation using various brushes, the noise and blur filters and gradient fills; they are all completely seamless. The possibilities are almost limitless.
To download any of the images above, right-click on them and selectfrom the pop-up menu. Save the image to your textures folder and test them out as materials in AutoCAD.
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