3D Toolkit: Curve Brushes

IMM CURVES
IMM Curves are specific IMM Brushes that allow for curved shapes to be drawn into a workspace atop a model. These IMM patterns follow a set curve, which is determined as the curve is drawn over the model. The IMM is then placed over this curve, following its length and orientation and placing multiple IMM instances along it. These instances join together to form one total mass. For example, chains, belt buckles or cables could be constructed from IMM curves. In the example of a chain, the individual chain links would follow the path of the curve and join together to form one swooping path.

IMM Curves can be created by importing multiple Objects into ZBrush. To demonstrate this process, I modelled a charging cable in Maya, separating the model into three objects - a top, middle and bottom section, which had their vertices aligned yet which were not conjoined. This was an important step as it clearly showed ZBrush where the front, mid, and end sections of the model lie, which could then be referred to in the creation of the IMM curve: the curve, when drawn, would begin with the top object and end with the bottom object, with the middle being stretched out and oriented to fit the path of the curve.

When importing the model into ZBrush, I used an export selection to export the three separate objects in the appropriate orientation. I could then insert these objects, OBJ files, into ZBrush. To import this, I utilised the "insert multi selection" functionality, which adds in each exported object as its own Subtool. To transfer these subtools into an IMM brush, I create a Polygroup for each subtool and merge them down into one tool. This functionally combines them whilst keeping them identifiably different, each polygroup acting as a different section of the model: the top, mid and bottom that ZBrush will use to construct the IMM Curve.

To create the IMM Curve Brush, I went into the "Brush" tab and used the "Create Insert Brush" functionality. Then going into the Stroke menu, I could select the brush to be a curve, turning off the "curve falloff". This means that the end of the curve will not taper, which could be used for applications such as hair. I then selected the "Weld Points" function, which should join together the vertices to create one shape. 

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This allowed my cable model to be used as an IMM Curve brush. With this, I went back and added more geometry in the midsection to make it more flexible. I did this by adding Edge Loops to the section. I could then draw my shape in more elaborate curving patterns.