Wrinkle

Carbon is very good at ironing out wrinkles in existing geometries, therefore removing unwanted creases which have been baked into the geometry. Using Carbon Cloth Flat Angle sets all existing angles, which larger than its value, to be flat. In Tailored mode, all reference angles are flat and the Flat Angle parameter allows to control the seaming angles’ limits.

But on the other hand, some creases are meant to be permanent. Typical cases for this include curtains, dress shirts with collars, skirts with pleats or pants with pleats.

The latter is used in this tutorial, which demonstrates how to set up and simulate permanent wrinkles, such as creases or pleats, for a Carbon Cloth node.

It is recommended to use the Tailored cloth mode for handling any types of garments that have been created using a virtual garment design tool. For introductory information on how to create a Tailored simulation with Carbon, please refer to Tailored Cloth Setup Tutorial before continuing with this tutorial.

Setting Up The Geometry

As pleats are hard angle overwrites on user-defined creases, it is crucial to ensure that the pleat lines are a part of the geometry when creating a virtual garment in a design tool. Otherwise, the pleat will not form a straight line and will look undefined.

_images/tutorial_wrinkle_start_ref.png

Start pose and reference panels of the pants.

The geometry setup for wrinkling comes from the painted attribute wrinkles. For introductory information about attribute painting and paint maps, please refer to the User Guide Painted Attribute Maps and Painted Attribute Maps Tutorial.

As geometry creases along edges, the reference angle between two faces that share an edge is determined by the average value of wrinkles for the two points on that edge.

_images/tutorial_wrinkle_reference_angle.png

Wrinkles controls the reference angle between two faces.

A painted wrinkles value of 0.5 sets a reference angle of 0 degrees between the two faces. This corresponds to a flat geometry, i.e. both faces lie in the same plane.

Therefore set the initial value for the whole geometry to 0.5 and afterwards paint all areas where wrinkling is supposed to happen. Paint maps range from 0 to 1 and are used as multipliers.

The Wrinkles Limit parameter in Carbon Cloth controls the actual angular wrinkles limit of creases. A painted value of 0 then corresponds to -wrinklesLimit degrees and 1 corresponds to wrinklesLimit degrees. The final angular value for each segment then calculates as follows:

With avg_{paint} being the average of two wrinkle point attribute values across a segment, angle = wrinklesLimit *(avg_{paint}-0.5) * 2.

Dealing with creases or pleats, it can be quite hard and tedious to use a Paint node for setting up the wrinkles paint map. Another way is to select all points of the geometry that should receive equal values and put them in a point group by adding a Group node.

_images/tutorial_wrinkle_group.png

Select and store and points on the pleat lines in a point group.

Then, create and set their wrinkles attribute value in an AttribCreate node. Default initializes all points and Value allows to additionally set a different value for all points in the provided Group.

_images/tutorial_wrinkle_attrib_create.png

Set the wrinkles attribute by using a AttribCreate node.

This method is very precise and flexible. For visualization purposes, it can be helpful to also add a Paint node and display the wrinkles attribute. The result is shown below.

_images/tutorial_wrinkle_paint_map.png

The wrinkles paint map on the pants.

The final graph of the geometry node also includes all steps needed for the Tailored cloth setup. Furthermore, add a point group to bind the top of the pants, as they would fall down otherwise, see also Avatar Cloth Setup Tutorial.

_images/tutorial_wrinkle_geometry.png

Network view of the geometry and the pants.

Setting Up The Carbon Cloth Node

After completion of the Tailored simulation setup, wrinkling involves one single and easy step. The simulation graph looks the same with or without wrinkling, and wrinkling is controlled by only one parameter - the Wrinkles Limit.

_images/tutorial_wrinkle_dopnet.png

DOP network of the simulation.

The Wrinkles Limit’s values range from -180 to 180 (degrees) and set the angular limit of the wrinkling, with negative values expressing an inversion of the wrinkles paint map. This can be useful if the initial paint map has been painted the wrong way around.

In this case, 90 is a suitable value to produce the expected creasing.

The simulation can now be run with the pleats clearly showing.

Recalculating The Normals

Finally, as the simulation output normals are averaged, it can be a good idea to re-import this geometry using a Carbon DOP Import node and then consecutively have the vertex normals along the pleats recalculated to make them look sharper. This can be easily achieved by adding all the points along the pleat into a new point group and then attaching a Normal node to it. Set the Normal node Group parameter to the newly created point group and select Add Normals To Vertices, and also set Cusp Angle to 0.

_images/tutorial_wrinkle_normal.png

Final result after applying a Normal node and recalculating the vertex normals for all vertices on the pleat point group.

_images/tutorial_wrinkle_result.png

Pants without wrinkles (left), with wrinkles (center), with wrinkles and recalculated normals (right).