Filtering Image Clips for Rendering

When using an image clip as a surface texture, you can define if and how it will be filtered when rendered. There are two ways to filter the image:


There is no filtering on this checkerboard image. As a result, the moiré effect at the far end of the grid is obvious.

This (usually unwanted) effect is caused by imprecise sampling of a dense and varied texture.

This checkerboard uses elliptical filtering to smooth the moiré effect.

Although this result could be achieved using antialiasing, this option is much less memory intensive and produces comparable results.

Elliptical Filtering

Elliptical filtering is usually used on high-detail textures that are moving near or far from the camera. This filtering process is much less memory-intensive than using antialiasing in the render options.

Elliptical filtering projects an ellipse onto the object's surface. The circle is elliptical (hence the name of the filtering process) so that it can cover all of the texture's pixels, which are then looked up and computed when a color value is returned for all the pixels in the circle.

You can find the elliptical filtering options on the Filtering tab of any Image shader property editor.

Using MipMaps (Pyramidal Mapping)

You can use pyramidal mapping — or MipMapping — to smooth textures when rendering. Mipmapping mapping performs a pre-blurring of a texture that is far from a camera.

The classic example is a very long checkerboard texture that seemingly goes off into infinity, but starts near the camera. As the grid gets farther away, the texture flickers and breaks up as the renderer samples only a single, far-away pixel.

This can be corrected with antialiasing, but it may become very time-consuming when rendering. Pyramid mapping blurs the distant texture so the render doesn't return a specific pixel color; instead, it returns an interpolation of several distant pixels. This solution is less time-consuming than antialiasing and yields excellent, realistic results.

To use mipmapping

  • Enable Generate MipMaps on the Texturing tab of the Image Clip Property Editor.

    You can specify how a texture is pre-blurred when it is far from or near the camera using the Texture Minification Filter (when a texture is far from the camera) and Texture Magnification Filter (when a texture is near the camera) parameters.