Edit UVs > Unfold

 
 
 

The Unfold feature lets you unwrap the UV mesh for a polygonal object while trying to ensure that the UVs do not overlap. Unfolding UVs helps to minimize the distortion of texture maps on organic polygon meshes by optimizing the position of the UV coordinates so they more closely reflect the original polygon mesh.

For example, if the initial shape of the UVs results in a distorted texture pattern on the surface mesh, you can use the Unfold feature to minimize the distortion because it attempts to maintain the UV’s relationship relative to the original surface mesh.

Related topics

Edit UVs > Unfold >

These are descriptions for the options in the Unfold Options window.

Weight solver towards

A bias setting that determines the weighting between two unfold solver types: local and global.

When Weight Solver towards is set to 0 (default) a local solver is used for the unfolding calculations.

When the Weight solver towards is set to 1 a global solver is used for the unfolding calculations.

When the Weight solver towards is set anywhere between 0 and 1, the unfolding results are based on the combined solver calculations.

A Weight Solver towards setting of 0 is recommended for the majority of unfolding operations and provides the quickest results.

Some polygon configurations can cause the Unfold feature to produce an undesired tapering effect on the unwrapped result. For example, the tapered shape from the thigh towards the ankle on a character’s pant leg may result in a more exaggerated tapering as a result of how the local solver works when it unfolds the UVs. When this occurs, the results can usually be improved by performing additional unfold operations with the Weight solver towards setting set to a value above 0 so that the global solver is taken into account. The unfold operation will take substantially longer, but the tapering effect will be reduced. Once the scale is more uniform, you can carefully pin UVs to control areas that were previously at different scales to ensure they don’t revert back. Once the UVs are pinned, you can perform subsequent unfold operations with the Weight solver towards setting at 0.

For an example of how this works see Solver weighting example.

Optimize to original

Specifies which polygon comparison method is used for the unfolding operation. This setting is only available when the Weight solver towards setting is greater than 0 and can be biased towards two comparison methods:

Face area

Compares polygons by comparing the area of individual UVs to the original faces of the polygon mesh.

Edge length

Uses a method that compares the length of the edges of the UVs to the face edges of the original polygons.

When the Face area/Edge length bias setting is set to 0.5 (the default) both methods of comparison have equal weighting in determining the final result. In general, this is a good starting point for the majority of unfold calculations.

Polygon meshes with high areas of curvature can have better unfold results when the bias is set towards Face area. This setting minimizes the buckling of the texture map in the areas of curvature. However, if the bias setting is set fully towards Face area, a shearing effect on the texture can occur as a result of the calculations attempting to work within the constraints specified by the Face area bias.

Pinning

Use the following options to unfold only selected portions of the UV shell.

Pin UV border

Maintains the position of the UVs along the poly shell’s border edge during the unfold operation. Use this option when you want the shell’s border edge to be unaffected by the unfold operation.

Pin UVs

Lets you perform the Unfold operation but pin specific UV combinations.

Pin selected UVs

Maintains the position of only the selected UVs during the unfold operation.

By default, Unfold repositions all of the selected UVs during the unfold operation and the unselected UVs remain pinned. This option reverses that default behavior. This option can be useful when specific UVs are already in a desired pattern when unfolded and you need some of the UVs to remain unaffected by subsequent unfold operations.

Pin unselected UVs

Maintains the position of only the unselected UVs during the unfold operation. This is the default setting.

When this option is on, Unfold repositions all of the selected UVs during the unfold operation and the unselected UVs remain pinned.

Unfold constraint

Specifies how the unfolding of the UVs will be constrained as they are unfolded.

None

The UVs will unfold freely in any direction during the unfold operation.

Vertical

The UVs will be constrained in the vertical direction as they appear in the UV Texture Editor.

Horizontal

The UVs will be constrained in the horizontal direction as they appear in the UV Texture Editor.

Maximum iterations

Specifies the maximum number of repeated calculations allowed for the unfold solver when calculating the final unfolded result if the Stopping threshold value has not been reached. When this maximum occurs, the unfold calculations will stop.

Tip

You can stop the unfold calculations at any time by pressing .

If the calculations appear to stop prematurely, it simply means that the Stopping threshold has been reached. The default is 5000. Setting the Maximum iterations higher than 5000 causes the Unfold feature to calculate further towards the Stopping threshold and lengthens the time for the unfold calculation.

If the Weight solver towards setting is any value above 0, you may wish to initially set Maximum iterations to a smaller value such as 50 for your initial unfold iteration.

Stopping threshold

Specifies a mathematical threshold to stop the unfold calculations. The value is based on an internally computed relative percentage of overall improvement when comparing the angles, distances, and areas between the original polygon mesh and the unfolded result. The unfold calculations will progress until this percentage threshold is reached or until the maximum number of iterations specified by the Maximum iterations setting is reached.

Setting the value smaller than 0.001 will result in longer times when unfolding. If time is not of concern, you can also set the Stopping threshold to 0 and allow the Unfold feature to calculate the best result.

Rescale

Resizes each final unfolded UV shell to match the Scale Factor once the unfold calculations are complete. It accomplishes this by first determining the surface area of the polygon mesh in object space (XYZ), comparing it to the unfolded UV meshes' surface area, and then scaling the UV mesh by that value.

This option is useful when multiple shells are unfolded and you require them to have a similar scale between them.

Scale factor

A ratio value that determines the amount of Rescale. A Scale Factor greater than 1 results in the UV mesh being scaled larger, whereas a Scale factor less than 1 results in the UV mesh being scaled smaller.

For example, if a polygon mesh had a unit size of 1 in the scene view, a Scale factor setting of 0.02 would result in the corresponding UV mesh having a unit size of 0.02 in the UV Texture Editor.

Keep history

When Keep History is turned on, the Unfold feature automatically recalculates the UV texture coordinate positions for the shell whenever the polygon model’s mesh is changed. This provides an effect where the texture appears to be distorted inwards or outwards along the surface when the mesh is deformed.

Turning Keep History on can result in long computation times when the polygon object is animated thereby affecting interactive performance. It should be turned on only when you specifically want this special effect to occur and are aware of the impact on interactive performance in your scene as a result.

The default setting is off.

Solver weighting example

The following example demonstrates how changing the Weight solver towards option in combination with pinning and aligning UVs helps to control the unfolded UV layout and the texture mapping that results.

  • A barrel shaped polygonal object is texture-mapped with a checker texture. Using the Unfold feature and performing an initial unfold with the Weight solver towards option set to 0 (the default) initially produces a tapered UV layout in the UV Texture Editor. The resulting texture map is skewed and distorted on the object.
  • A second unfold operation is performed with the Weight solver towards option at 0.6. This unfolds the UVs in a more global manner and reduces the tapering that previously occurred. The UV layout is more predictable, but there is some overlap of UVs in the lower left corner of the UV mesh resulting in overlap on the texture.
  • Repositioning and pinning the corners of the UV mesh and performing another unfold with the Weight solver towards set to 0 further relaxes the UVs and removes the overlapping region.
  • The top and bottom rows of UVs are aligned and a final unfold operation is performed with the Weight solver towards option set to 0 with the borders pinned.

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