Tools > Color > Generate Texture (available when at least one polygon object exists) creates a texture map on the active polygon object.
A "simple" polygon object with color stores a color attribute in each vertex. Therefore, high-resolution color requires a dense polygon mesh. But when a dense polygon mesh is undesirable, and you use a variety of polygon-altering functions such as Polygons > Decimate or Polygons > Relax, the per-vertex color can become so washed out or distorted that acceptable color resolution is lost. Therefore, the industry developed the concept of a texture map to maintain precise color even with an altered polygon mesh.
A texture map is the mapping of a high-resolution image to a lower-resolution polygon mesh. The high-res image and the coordinates become part of the lower-res polygon object such that their existence is transparent.
To use this function:
Load polygon object A with color (per-vertex color), then remove its color using Tools > Color > Remove Colors.
Optimize the colorless polygons using functions like Polygons > Decimate or Polygons > Clean, then save it as object B.
Import object A (such that both A and B appear in the Model Manager), and make B active in the Model Manager.
Run Tools > Color > Generate Texture. Select object A as the input object. Upon completion, B has its modified mesh and the original color of A.
Alternate scenario:
Designate a colorless polygon object the active object in the Model Manager
Run Tools > Color > Generate Texture, press the Apply button, then then the OK button.
The previously colorless polygon object has been assigned a white image with a texture map. This prepares the polygon object to be used by other functions that operate on texture maps.
The controls and indicators are:
Color objects group - specifies objects in the Model Manager that are to be processed.
Object Name dropdown (a list of polygon objects in the Model Manager that have color) - specifies the object whose existing color will be mapped to the active object. When the goal is to convert one object's per-vertex color to a texture map, make it active before starting this function and pick its name from this list.
Statistics group - presents details of the resulting texture map.
Texel Size decimal field - the average size of all actual texels.
Texture Maps integer field - the actual number of texture maps. (Depending on complexity of the active object, multiple texture maps might be created.)
Max. Texture Size - the largest texture size in any texture map.
Resolution group - sets constraints for the resulting texture map.
Min. Texel Size decimal field - the lowest acceptable size of a resulting texel.
Max. Texture Maps dropdown (One, Two, Three, Unlimited) - the maximum number of texture maps that can be generated. (Depending on complexity of the active object, multiple texture maps might be created.)
Max. Texture Size (256x256, 512x512, 1024x1024, 2048x2048, 4096x4096) - the highest acceptable size of any resulting texture map.
Options group -
Observe Boundaries checkbox - disallows any texture region from crossing a red boundary line.
Use Current UV Space checkbox (available only when UV coordinates already exist because the active image already has a texture map) - causes the input image (from Object Name) to be projected onto the active image according to existing UV coordinates, without first generating new UV coordinates. Use this option when the active object already has a texture map and you simply want to apply the color from a different input image (from Object Name).
Texture Display group - A texel is the smallest uniquely colored unit on the surface of any colored object. When you zoom way in on a colored image, a texel looks like a uniquely colored square. When you zoom out, a texel gets as small as a hardware pixel, or smaller. The following settings specify how pixel color is determined (in this application only, not in exported files that are loaded by other applications). Typically, accept the defaults.
Min. Filter dropdown ("Minification" Filter, the opposite of "magnification") - specifies methods of rendering pixels when texel size is smaller than pixel size.
Nearest - a pixel assumes the color of the nearest texel.
Linear - a pixel assumes color based on the four nearest texels.
Mipmap - a pixel assumes color based on best-matching mipmap.
Linear Mipmap - a pixel assumes color based on best-matching mipmap and the four nearest texels.
Mipmap Linear - a pixel assumes color based on two nearest mipmaps and the the nearest texel.
Linear Mipmap Linear - a pixel assumes color based on nearest mipmap and the nearest texels. (The "linear" choices create better visual quality at the expense of speed.)
Mag. Filter dropdown ("Magnification" Filter) - specifies methods of determining pixel color when a texel comprises multiple pixels
Nearest - a pixel assumes the color of the nearest texel.
Linear - a pixel assumes color based on the four nearest texels. This can create a blur where one texel meets another.
OK button - generates a texture map, saves changes to the active object, and closes the dialog.
Cancel button - terminates the dialog without saving changes to the active object.
Apply button - generates a texture map. Next, press OK to close the dialog, or change the parameters and press Apply again.