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Troubleshoot painting

The following table lists common problems and possible solution related to painting:

Problem/Error Message | Possible Solution
--- | ---
Paint strokes appear uneven or with a stuttered appearance. | The Stamp Spacing property is set too high. Decrease the Stamp Spacing value and try again. Check that the Randomize property is turned off.
Paint cannot be applied to some regions of the model. The unpaintable regions appear as streaks or paint artifacts. | Artifacts can appear when painting on a model whenever the UVs overlap, are positioned too close to each other, or are positioned too close to the UV tile border. UVs should be positioned so an empty region (4 to 6 pixels in width) exists along the outside the perimeter of each UV shell to account for the necessary edge bleed that automatically occurs when painting. View the UVs for the model by clicking the UV View. Dolly and track the camera within the UV View to determine if any of the above described situations exist. If so, you must re-edit the UVs in another 3D modeling application equipped with UV editing tools (Maya, 3ds Max, and so on) to correct the problem and then import the model again or import only the UVs using File > Import UVs. Keep in mind that if you shift the UV positions when you re-edit them, any previous paint work will not be registered. For more information, see Prepare a model for painting.
Paint applied to one model appears on other models in the 3D View. | Models imported to Mudbox are assigned the Mudbox Material by default. When you paint on a model, the paint layer creates a texture map behind the scenes that is applied to the associated material property (diffuse, bump, and so on). When models share the same material, they also share any paint that is applied to any of the models unless the UVs for each model are laid out in separate tile spaces. To avoid this, assign separate materials to the various models so any paint you apply is unique to each model. If you want the models to share the same material, lay out the UVs so they do not overlap or lay them out in different tile spaces before importing to Mudbox. For more information, see UVs overview and Paint across multiple UV tiles.
UVs did not appear in the UV View initially but I was able to paint on the model. | Mudbox does not apply paint to a model unless there are UVs present, so UVs must exist on a lower subdivision level. UVs only appear in the UV View if they exist for the current subdivision level that is currently displayed. As soon as you create a paint layer on a subdivision level without UVs, Mudbox automatically creates them for all levels in-between the base level and your current level. In the 3D View, press the Page Down key repeatedly until the UVs appear. If you want to recreate UVs on a higher subdivision level, press Page Up in the 3D View until the desired subdivision level is displayed, then select Mesh > Recreate Level UVs.
When viewing the 2D painted image in the UV View, the painted regions appear white. | Check the current subdivision level on the model. At high subdivision levels, the UV mesh will appear as a very dense white mesh in the UV View. Press the Page Down key to display a lower subdivision level to reduce the density of the UV mesh and reveal the painted image in the UV View.
Air brush paint strokes appear with uneven blending when the paint layer color channel is set to 8 bits. | Artifacts (concentric rings in the brush stamp) can appear in an air brush paint stroke with particular color hues (cyan, gray scale) whenever the Brush Size is relatively large in relation to the layer resolution. This occurs due to the limited bit depth in the specified color channel. If this occurs, specify a paint layer that is 16 bits in depth (for example, OpenEXR 16 bit Floating Point RGBA).
Cannot erase paint from the model. | Ensure you have the correct paint layer selected in the Layers window prior to using the Paint Erase tool. Paint Erase erases paint only on the selected layer. Ensure the selected paint layer is not locked. A lock icon appears to the left of the layer name if the paint layer is locked.
Two paint cursors appear on the surface of the model when painting. | The Mirror property for the tool is turned on. If you do not want to apply paint in a symmetrical fashion, turn off the Mirror property. For more information, see Paint properties.
Stamp or stencil images appear tinted when applied to a model as a paint layer. | Ensure the Color property of the paint brush is set to white. This ensures that the original color of the image is maintained. For more information, see Change the paint color.
A semi-transparent image appears in the 3D View. | A stencil image or image plane may still active for the active camera view Turn off the stencil or image plane in the respective tray or property window.
An additional file appears in the files directory that stores the paint work associated with my .mud file. Its name contains the text Background. What is this file used for? | An image file containing the text Background in its filename gets saved to the files image directory when a model is saved after painting. This small image records the model's default material color so that it appears through any unpainted (transparent) regions of the paint layers. Otherwise, unpainted (transparent) regions would appear incorrect when rendered. If a model contains multiple UV tiles, there will be one background image file created for each UV tile per layer channel.
Model appears with multicolored square-shaped tiles on its surface in the 3D View. | Models with multiple UV tiles are automatically displayed with their textures turned off to reduce graphics memory usage and optimize interactive performance. The multi-colored tiles indicate the unloaded state for the texture tiles. You can manually turn on or off the display of textures for any UV tile using the arrow keys. For more information, see UVs overview and Hide and show UV tiles on a model.
The following message appears when attempting to paint on a model: “To paint this area, you must first load the UV tile. Hold the cursor over the area and press up arrow to load or unload the tile.” | This message indicates that the area of the model you are attempting to paint is associated with a UV tile that is currently unloaded. You must display the UV tile before you can paint on it. This is a feature for optimizing video memory. For more information, see Hide and show UV tiles on a model.
Noticeable pauses occur between the stroke and it updating on the model when painting high resolution paint layers on models containing multiple UV tiles. | To improve performance under these circumstances, turn off the Undo feature for painting by selecting (Windows) Windows > Preferences > Paint > Disable Paint Undo or (Mac OS X) Mudbox > Preferences > Paint Disable Paint Undo.
Cannot paint on a region of the model. The following message appears: Only separated tiles are supported | One or more UV shells on the model are positioned across a UV tile border. UV shells must be completely contained within a UV tile. For more information, see Prepare a model for painting. For more information on viewing the model UVs see, View painted images with UVs.
The following message appears when painting on a model: To paint this area, you must first load the UV tile. Hold the cursor over the area and press the up arrow to load or unload the tile. | This message indicates that the area of the model you are attempting to paint on is associated with a UV tile that is currently unloaded. You must display the UV tile before you can paint on it. This is a feature for optimizing video memory. For more information, see Hide and show UV tiles on a model.
The following message appears when displaying all UV tiles on a paint layer: Displaying many texture tiles may consume available video memory and degrade performance. Continue? (Yes, No) | This message is a reminder that displaying all texture tiles on the model at once may consume all of the video memory depending on the number of tiles and the resolution of the textures on each. When this occurs, the system performance may be slower than expected. For more information, see Hide and show UV tiles on a model.
Painted regions on multi-tile model do not appear in the UV View. | When multiple UV tiles exist on a model, only the paint associated with the currently loaded tile(s) appears in the UV View. To load and unload UV Tiles, see Hide and show UV tiles on a model.
The paint layer appears transparent except for the regions that were painted. | This is correct. A paint layer is fully transparent until you apply paint to it. The color that appears behind the paint is the diffuse color of the assigned material or the paint layer below it.
The Dry Brush is applying paint to both the raised and recessed regions of the sculpted surface. How do I constrain the brush so it applies paint to either the raised or the recessed features, but not both? | Reduce the Size property for the Dry Brush. The Dry Brush works by calculating a reference plane whose height above the models’ surface is based on the average height of the vertices that appear within the brush ring. Paint is applied to the faces depending on whether they appear above or below this invisible plane. As this reference plane is dynamically calculated as you paint with the brush, a large brush ring area may result in the tool determining a plane height that is not optimal.