And this averaging process is a root cause of losing quality in alpha tested materials. The simplest filter that can create a mipmap will use an average of 4 neighbor pixels to generate one pixel for the next level. I want to mention two of them bilinear filter and Kaiser filter. In computer graphics a lot different filters have been developed (with different usages and characteristics, I won’t go into details for this text). Generating a downsized version of the original image can be done by using algorithms called filters. Each level is two times smaller than the previous level.Ģ) The material sampler filtering type must have proper value (in OpenGL GL_LINEAR_MIPMAP_LINEAR). Mipmaps are downsized duplicates of the original image and form a chain of images. GPU needs to have two things:ġ) material textures must have mipmaps. Mipmapping is a technique in computer graphics that was developed to help avoid aliasing artifacts (shown in Figure 2) and thus render a better quality image. This problem occurs because of the way mipmaps are generated for those alpha tested textures. In the standard way of generating alpha textures an object which is using this material will tend to degenerate (disappear) when moving far away from the camera. Your browser does not support the video tag. Let the following video below be an example of this issue. It can be noticed when a rendered object (with applied cutout material) is far away from the camera. These types of materials are commonly used to render vegetation, fences, impostors/billboards, etc.Īlpha tested materials have some issues. When shaded pixel’s final alpha value is less than this threshold value (threshold value is constant for the instance of the material and a typical value is 50%), it is clipped (discarded) and will not land in the shaders output framebuffer. In a very basic form, a material (shader) of a rendered object can discard processed pixels based on the alpha channel of RGBA texture. This technique which I want to share with you consists of two neat tricks that can improve the quality of alpha tested (cutout) materials.Īlpha test is an old technique used in computer graphics. It's about alpha tested (also know as cutout) materials. Today I want to share with you a trick which my colleague from previous job mentioned to me a long time ago.
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