ZBrushCentral

Trim Curve Defaults?

ZBrush Usage Questions
#1

Hi, I’m new to ZBrush and I’m trying to figure out the default behaviour of some of the tools. Maybe I missed something in the documentation.

Is the trim curve tool supposed to create a twist like this through the geometry (see image - I was using the trim curve on a polycube). When I use the trim curve brush with an orthographic camera aligned on the X & Z axes, it seems to create a twist along Y axis. The behaviour seems connected to the strength of the anchor points.

  1. Is this the default behaviour and is there a way to control it/ work around it (how can I use a curve to cut perpendicularly through the front surface)?
  2. By pressing ALT, I can add anchor points but the weighting seems to increase based on the distance from the last anchor point. For me it seems difficult to get a simple smooth S-curve.
  3. Is there a way to control the strength of the anchor points (i.e. using the brush size/ focal shift, etc.)?
  4. Anyone know what the mathematical model is behind the anchor points (i.e. what is the math behind the type of splines, - are these bezier curves, etc.)? I’m having a hard time visualizing the way curves are supposed to behave.

Thanks.

Attachments

trimCurve.JPG

trimCurveAnchors.JPG

#2

i think zbrush controlling the curve ONLY by the distance of points(maybe) , in you case,you can get the first result if each point have a short distance , but the length probably not enough to go through the whole mesh,you can zoom out to let you mesh to fit the curve…alternatively ,press alt more frequently to create more point…

#3

Thanks very much for the reply, that’s kind of what I thought, but the question seemed worth asking anyway.

From my perspective I find the behaviour of the anchor points less than ideal, but I can live with it. You’ve answered questions 2, 3, and 4. I found an answer to question #1 myself this morning…

  1. Yes, it’s the default behaviour of the TrimCurve brush. But it’s not the tool you should be using if you want to cut perpendicular to the surface. Use the ClipCurve brush (or any of the clip brushes but change the stroke to curve).

I figured I was doing something wrong.

#4

Trim curve will cut, erase and closeholes in your mesh. If you want it to have flatten results in your piece use Clip curve insted.