A useful program to have when conducting an image quality analysis is TheCompressonator, which was written by ATI and is a developer tool used to compress textures and create mipmap levels. Version 1.20.1042 was released in July and contains a number of enhancements and bug fixes.

The feature of TheCompressonator that is exercized in this examination is the texture and image comparison feature. TheCompressonator compares two images and will visually point out differences between them. When two similar images are compared, the differences may only become visible after the brightness level is increased in TheCompressonator.

The examples below illustrate the output from TheCompressonator and consists of an image with 8X anisotropic filtering on the left and an image with 1X anisotropic filtering on the right. The middle image highlights the differences between them, which can be brightened and enlarged. The brightness was increased by 400% in the second image and by 1600% in the third image.

TheCompressonator Output

Default Brightness

Difference Brightened by 400%

Difference Brightened by 1600%

The following javascript applets will demonstrate the effects of the various levels of anisotropic filtering that are available in Doom 3. Clicking the links underneath each image will reveal the screenshot that was taken with the chosen level of anisotropic filtering enabled. Each image in the comparison averages around 50 KB in size.

After each image is downloaded and saved in your browser cache, you will be able to quickly switch between them to see the differences in the levels of anisotropic filtering. As you switch between the images, subtle changes will occur. The most noticeable changes will occur during the transition from 1X to 2X anisotropic.

High Quality Image Setting - Scene 1

1X Anisotropic | 2X Anisotropic | 4X Anisotropic | 8X Anisotropic

High Quality Image Setting - Scene 2

1X Anisotropic | 2X Anisotropic | 4X Anisotropic | 8X Anisotropic

High Quality Image Setting - Scene 3

1X Anisotropic | 2X Anisotropic | 4X Anisotropic | 8X Anisotropic

In many cases, applying anisotropic filtering beyond a 4X level becomes counterproductive.

Next Page: Direct3D Texture Filtering