howdy,
so just starting to play with the neat-o-ness that is zb4 and i just noticed straight off that the clip brushes work except for the rectangle one…
instead of creating a nice clean cut, it smears the edges into a flat sheet that goes past the edges.
anyone else or just me?
happened on medium poly objs and higher poly objs.
jin
Yeah I’m getting this as well. I cant seem to actually get the rectangle to clip anything without created some rectangle shaped polys stretched everywhere.
Same here and not only with the rectangular brush.
Wouldn´t it be possible that the clip brushes created new geometry instead of just smearing the old one around? This way one could also build tunnels through objects. Zbrush can already construct loops around a specified area with grouploops. Wouldn´t it be possible to create similar loops around an area marked by the clipping brush, delete the mesh within (or outside of it) and construct a new surface between the holes? More or less like a boolean operation.
One should be able to turn this behavior on or off so you can also work with the current version, if you need to.
Yeah it looks like a lot of the clip brushes are having issues. I can get a fairly consistent result with the clip curve brush once I figured out how to use it but it still produces some errors from time to time. The circular clip brushes only seem to work fairly well if I use very shallow cuts into the edge of an object. Anything deeper and i get some mess of faces flying out of the object. The rectangular clip brush fails 100% of the time for me though. I’ve never once gotten a decent result from it. It just creates these weird skewed box polys everywhere.
Turn off symmetry and try again.
Its off. Thats one of the first things I checked. Just tried again and no luck. The rectangle clip just makes a mess.
Yes, Symmetry makes a big mess when you try to clip.
One thing I read in the manual though, is that in order to cut out you need to hold down CTRL SHIFT and ALT and make sure the crosshair isn’t over your mesh, i.e you need the crosshair to be outside the mesh, otherwise it will push out the geometry.
But there are definitely some odd little quirks with the clipping tools though, as sometimes it seems to work and other times not so well.
yeah tried it again with symmetry off and the little plus in the center of the square nowhere near the mesh…
it still smears out the polys in big flat sheets around the cut…
but it works with corner cuts - using the corners of the clip brush… but if i just want to flatten down the bottom of a sphere, say to make a round sculpture that will stay on a table, and use the rectangle clip to just clip away the bottom 5th of the sphere or something, it just smears polys.
curious because the clip seems to be working flawlessly for the demo guys and their demo videos.
anyone have any insight?
jin
I don’t think you are using it correctly. The clip rectangle will remove geometry outside the rectangle. If you hold Alt it will remove geometry inside the rectangle but it can’t be used to create holes.
http://www.pixologic.com/docs/index.php/New_Brushes%2C_Settings_and_Behaviors#Clip_rectangle
I havent been using it to make holes. All of my goals with it were pretty simple. A good example is creating a sphere and then use the rectangle clip to shave off a side of the sphere creating a flat circle. Instead it shaves off the side but then creates a giant square shaped poly. When I get home I’ll take some screen shots.
Perhaps I should be using the curve crop tool instead?
Wow these things are a lot more difficult to use than they look in the demo vids. I also saw this problem, and I’ve got some thoughts here.
Overall, you can only nicely clip convex areas, as determined by the planes drawn by the clip shape. In other words, imagine the intersection of the clipping plane and and your object… this will be a curved, two dimensional shape. If you look through this shape at the portions of the object you’re trying to clip off, every part needs to fit inside of the shape, otherwise the points will ‘land’ on the clipping plane outside the surface of your model, creating a ‘wall’ of polys. To understand how this works for the circle and curve, note that the curved sections can be made up of skinny rectangles like the sides of a polygonal cylinder.
in ALT mode, The center ‘point’ of the rect clip is actually a pair of horizontal and vertical lines. If either of those lines intersects your object, the behavior of the perpendicular plane touching the model changes to the ‘push mode’. Eg. say you have an object that is angled on the screen, and you use the rect clip brush in Alt (subtraction) mode, expanding it so the corner falls inside your model, but the center point remains outside. If the top or bottom line of the rectangle you’re drawing is half or more over your model, polygons will be pushed along the length of the line. If the lines are more than half ‘off’ the model, the clip behaves as expected. All four sides of the rectangle behave in this way. In most cases, you can draw your clip box far enough away so that the lines are less than bisected by the edge of the model (scale down the model and use the zoom window to get a better view if necessary 
The Circle clip also has this property – if the invisible center lines intersect your model, the polys will be spread along the curve ‘pointed to’ by the radius line. This is hard to explain.
Basically, when using alt mode for both the circle and rect clips, ensure that any parts of your model that you wish to clip away fall wholly within one of the quadrants created by drawing horizontal and vertical lines from the center point. (whew) (I call this the Quadrant Rule
The curve clip also has similar behavior, but is much harder to understand and explain. Fortunately, something about how it works makes it much easier to get the clip you expect. In many cases, it may be better to use the curve clip instead of the circle and rectangle for clipping off portions of your model.
Clipping using the rect clip so that the clip portion falls within a quadrant, but the corner lies outside the model will cause the polygons to spread out along the clipping plane in a direction away from the center of the rectangle. To avoid this, place the corner of your clip rect as close to the edge of your model as possible (the zoom window can help!)
Masked areas count as ‘off the model’ for the center point. Clipping so that masked areas are in the portion of the model you’re trying to clip causes ugly stretching, but clipping so that masked areas are kept can help avoid messy results.
the clip tools are infinite in the z direction, so anything done to the front of the model affects the back. This is very noticeable when using the ‘push’ mode (centerpoint on model)… .mask or hide the back to avoid it this problem. In general, masking or hiding seems to be very important for complex models. Note, clipping in push mode too near a mask or hidden point will cause ugly stretching.
Clipping in push mode without any masking at all with the (ctl+space) bradius on will distort any portion of your model that isn’t masked as all the points try to collapse onto your clipping shape. Low bradii look to create some interesting effects though
when clipping arbitrary shapes (like cutting the hand off a model) it seems to be easier to first use the curve clip, and repeatedly clip at angles to pare down the larger portions (the hand) into a wedge shape below where you want to clip.
Symmetry seems to work fine, but ALL of the symmetry shapes follow the above rules, meaning it can be difficult to get nice clips on complex shapes.
When clipping pieces off of a model (say lopping off a nose), it works best to not use the alt mode, but instead the regular mode, and select what you want to keep (eg to cut a sphere in half, use the rect clip and select the half of the sphere you want to keep.) Especially in the case of the rect clip, this tends to create a much nicer ‘projection’ on the clipped area.
I started writing this agreeing that the brushes seemed to be broken. I think I figured them out now though. Note, most of the demo videos show people using #11, the curve clip, and such. Once you figure out how to use these according to the items above, they seem to work pretty well.
right - not using it to make any holes.
like i said, just trying to use the rectangle clip to flatten the bottom of a sphere so the sphere can rest on a table (for example).
it won’t make a clean cut so that there’s a flat circle at the bottom of the sphere but instead smears polys out off the sides of the circle so you get a big rectangular mash of polys surrounding the “base”.
jin
Thanks for the info oofnish, but if you are correct I’d prefer not to use them as that is far too much information to swallow, especially since these tools should be fairly straight forward.
To me dragging a rectangle along the edge of a shape should clip it, but instead there is usually some weird behaviour, namely the exploded plane.
Still, it’s early days yet and I’m overwhelmed by ZB4 as there are so many new things to work out. So I think I’ll take a break and come back tomorrow.
oooooooo
good catch! i just tried to make a flat area on my sphere and using the ALT mode creates a mess… not using the ALT mode and just putting the rectangle around the portion i want to keep works beautifully.
this would have stymied the heck out of me because it just seems more natural for me personally to rect select the area i want to get rid, not the area i want to keep.
actually, ALT mode seems to be broken then. it should work just like the inverse of the non alt mode (i.e. there’s no reason it should not work as well) so hopefully, they’ll work this out.
can marcus, beta testers or mods confirm that ALT mode on rect on a sphere (for example) is broken?
jin
Yeah great info Oofnish! That has helped a lot. I’ll make sure to follow those rules in the future. Sounds like they might need to make a slightly more detailed description of how these tools work than they did
Thanks, Oofnish,! Anyway, too many rules and restrictions for such useful tool, seems they are really broken. Hope, Pixologic will repair clip brushes soon (as well as many other bugs of zb4-for me it still not usable in pipeline)
I agree that the Clip Rectangle in Alt mode doesn’t work so good. I’m sure the development team will take note of your concerns.
Hmm. It doesn’t look like any of these issues have improved in R2.
I’m having ‘extrusion’ problems both with the clip rect’ and clip curve. In spite of avoiding the ALT-inverse trick.