Paint tools in Mudbox let you apply digital paint to your high resolution 3D models. Select a paint brush, create a layer to paint on, and paint your model in the 3D View.
Two paint modes are available:
You can also apply images as paint using brush stamps on the model, like a decal or tattoo. See Paint using brush stamps.
Stamps and stencils let you create different effects than using the Paint Brush tool alone.
When you paint on a model in Mudbox, the paint is applied to a paint layer. Paint layers let you keep track of the 2D bitmap image(s) you create as you paint. Layers are similar to transparent pieces of acetate that let you separate paint between one layer and another. See Paint layers overview.
When you paint on a model, you create one or more 2D bitmap images that are positioned on top of the base shading material.
If your model has UVs, the accurate positioning of your painted images on the 3D model is based on the location of the UV texture coordinates (UVs) for the model. This UV mapping correlates the pixel locations on the 2D image you paint to the surface of the 3D model. If your model is set up for PTEX painting, the position of painted images on the 3D model is based on automatic per-face mapping (each base face of the mesh has its own map).
When needed, UVs are usually created in the polygonal modeling application when the model is created. You can tell if your model has UVs by switching to the UV View. For example, any of the default sculpting templates in Mudbox have UV texture coordinates. (The UV View is also useful for evaluating how your painted image looks in relation to the UV texture coordinates.)
To create a quick set of rough UVs in Mudbox, you can select Mesh > Create UVs from the main menu bar. See also UVs overview and Prepare a model with UVs for painting.
The bitmap images that you paint are automatically saved with your Mudbox file (.mud) in a separate sub-directory at the same location as the .mud file. This image file can be used with other 3D rendering applications such as mental ray or RenderMan. (See also Save or export paint layers.)
By default, at least two images are saved for each layer: a background image that represents the material background color, and an image containing the information you painted. Alternatively, you can export a selected layer and save your painted images in any of the image formats that Mudbox supports. See Image formats.
Behind the scenes in Mudbox, the Gigatexel Engine works automatically and seamlessly to let you work with enormous texture datasets. Depending on your hardware configuration, you can paint high quality assets with enormous amounts of detail, without ever having to manually load and unload texture tiles.
When you're working with large textures, the engine starts to operate as a buffer between your paint strokes and texture images, having you paint on lower resolution proxy images while storing paint to the full resolution image. Mudbox automatically loads any tiles positioned in front of the current camera view, eliminating the need for you to load tiles manually.
Your paint strokes always look accurate in your scene and are safely captured in your high resolution textures, and the interactive performance of Mudbox is maintained, meaning you can continue to zoom, track, and tumble smoothly in the 3D View as you work.
As you paint large textures with the Gigatexel Engine turned on, a buffering progress indicator 
may display occasionally as Mudbox loads and unloads texture tiles, or writes your paint strokes to the underlying high resolution
textures.
If you find that the buffering indicator appears at inconvenient intervals or interrupts your work, you can press the Composite Paint Strokes hotkey (apostrophe key 
) to force the Gigatexel Engine to synchronize textures on demand. (You can change this default hotkey in the Hotkeys window.)
Although the Gigatexel Engine is designed to work silently in the background, advanced users can control the texture capacity handling options using the preferences Use Gigatexel Engine and Paint Buffer Memory Budget. If you prefer to turn the Gigatexel Engine off, turn off the Use Gigatexel Engine preference.
Prepare a model with UVs for painting
Prepare a model for PTEX painting
