Wall Worm 4.0.48+ has proper support for using the Crop functions in a Bitmap Texture. This feature is very convenient when you want to apply specific sections of a texture atlas to parts of your geometry without having to do extensive UV editing. It also has the advantage of allowing you to update a bitmap (including the locations of elements in it) without having to re-apply UVs. This function works for models when using the WW SMD Exporter, WW Pro SMD Exporter and WW Pro DMX exporter. It also works for brushes in the VMF Exporter. 

You can download the example scene from the following video to explore the creation of the wood texture atlas as well as the usage of the crop functions: Using Bitmap Crop in Wood Prop

When to use the Bitmap Crop

The bitmap crop function has certain use-cases where it is very convenient. However, there are other times that this method is either inefficient or even ineffective.

Conditions for Effective Use

• You are using a texture atlas where each texture in the atlas has its own, distinct, rectangular region.
• The polygons using the texture cannot generally expect to tile in both U and V (only one axis can properly tile).
• For tiling textures, the UV of the target polygons should fill an entire UV space in the axis that is not tiling.

Conditions Not Conducive of using Bitmap Crop

• The sub-textures overlap each other's bounding areas.
• You need to tile the textures in both U and V.

Using Bitmap Crop

To use BitmapTexture crop, open a bitmap in the material editor and look for the Cropping/Placement group in the Bitmap Parameters rollout.

1. Turn on the Apply button.
2. Change the U/V/W/H values in that group to the desired cropping (or click the view Image button and visually set the crop).
3. Set the type to Crop (the Place setting is not supported).

Known Issues

• Limited Tiling Support. You can only tile in one axis. Although 3ds Max itself will allow you to tile in any other arbitrary situation, this will not work in the exported scenes because these crop parameters are applied to the mesh UV transformations on the exported geometry--and there is no crop function for most Source shaders.
• Prior to to WW 4.0.48, the vertical UV coordinates were often incorrect.