Let's Learn Blender! #7: Knife & Bisect tools!

[Music] hello my name is colin and this episode of let's learn blender we'll be talking about two of blender's 3d modeling tools first the knife tool the knife tool is used to let you create custom edges in pretty much any direction on any face of the surface of a mesh that you want it's a super powerful tool and the second tool we're talking about is called the bicep tool which lets you cut clean through a mesh and what that means that you're cutting basically a loop around your mesh wherever you want and you can even adjust where it is and the angle that cut through the mesh is facing and you can even use the bisect tool to remove or chop off part of a mesh and even cut a mesh into two with a few extra steps so we'll be talking about these two tools in this video this will be a little bit of a shorter video in this series we'll go ahead and put on the bottom of the screen right now how you can help me out by clicking like subscribe and the bell icon also if you've not checked out the rest of this video series on youtube this is my tutorial series called let's learn blender i'll put a link to this whole series up on the top of the screen right now so go ahead and check that out so diving into the knife tool in blender the knife tool is a tool that you access while you're in edit mode of a 3d mesh object in blender so of course with a mesh object selected you press tab to switch from object mode into edit mode the knife tool is one of the tools along your side toolbar i'll go ahead and drag the edge of my toolbar to make it a little bit wider so i can see all the tools on the screen now the knife tool is right here and if i select it you will notice that my mouse cursor if i go ahead and zoom in is now a little picture of a knife and all i have to do here is click anywhere on the surface of my mesh object in edit mode to start creating a cut in other words an edge that starts with a vertex and runs to another vertex now there are a few things to keep in mind here if you create a cut on the surface or an edge on the surface of a mesh an edge can't just end in the middle of a face so i'm gonna go ahead and click just on an edge and it'll kind of snap if i'm not exact to that edge and you can see when i click it creates a green square which is a vertex and i can move my mouse i'm not holding anything down right now and i can simply click on another edge and that creates the beginning of a cut and now i could keep going but i'm going to go ahead and make that edge that cut permanent simply by pressing the enter key on my keyboard when i do that now of course if i switch over to my select tool and i'll go into face selection mode i can select either of those two faces and i can do whatever i want with them let's say i could select this face and press the e key on my keyboard to extrude i can move my mouse and click of course the e key on my keyboard is the extrude tool and so now i have an extruded face right there now you don't just have to make one cut from edge to edge the knife tool is a lot more powerful than that if i go ahead to this other side i'll orbit and pan over so you can see this side a little bit better if i use the knife tool again and start on the same kind of upper edge i can make a zigzag pattern creating new vertices along my cut in the middle of a face so i'm going to click down on this edge usually go from edge to edge typically so i'm going to click and you can see i can keep going with this cut or of course i can press the enter key on my keyboard or the return key and that completes that cut and so now if i go to the selection tool and i go to face select mode and i select either one of these faces they are in fact faces now they are n-gone faces that means they are faces with more than three or four sides but they're still faces in facelike mode i could tap the e key and extrude and yeah you can see i've got a pretty silly looking extrusion or face here extruded out it is important to note that when you're using the knife tool you cannot simply cut a hole in the surface of a face so if i want to create let's say a square hole in the middle top of my cube i could cut from there to there i'm just clicking now with my knife tool and i can complete this cut you can see that if i press the enter key on my keyboard it doesn't just let me create a face in the middle of another large face you can't do that in blender so it automatically created connections or connecting edges from my middle face out to a couple of corners just based on what it thought would be best for the faces on the top of my cube so you can't just have a face in the middle of another face something else you can do with a knife tool is you can create new separate cuts before you press enter to finalize the cuts that you've just made let's go and see what i mean if i go back to my knife tool and i create a cut from this corner if you just click it'll snap to that corner or to that vertex and i click on this vertex well maybe i want to cut from there to there but then i want to let's say create another cut from here to here before i press enter on my keyboard to make those two cuts permanent i can simply do that by pressing the letter e on my keyboard i'm not sure why it's letter e it just is but when you press e it kind of finalizes that cut and now i can orbit around and create a new cut here to there in fact i'm going to press e on my keyboard again and i'm going to create a cut from oh let's say that bottom corner down here up to there and i'll tap e and start from here and go to there and now if i press the enter key on my keyboard all of those cuts that i just made are finalized so now i could go ahead to my selection tool and i could select let's say that face and that face and tap e to extrude them out and maybe i could select this face and this face and tap e to extrude them out and i could select this face and tap e and extrude it in so there's a fairly interesting geometric 3d shape that we've created fairly quickly using different options in the knife tool now the knife tool has of course this active tool here on your toolbar but if you just want to have your selection tool enabled and quickly get to the knife tool the legacy keyboard shortcut in blender is the letter k on your keyboard k is for knife and the reason i'm showing you this is because the legacy k version of the knife tool has a few more options and they are listed on the bottom information bar at the bottom of blender's interface so you can see down here i'll go ahead and zoom in that if you press the enter key on your keyboard it confirms a cut if you press the escape key or right mouse button it cancels your current cut with the knife tool if you press the left mouse button it defines or starts a cut if you double tap the left mouse button it closes the cut the e key as we've covered before makes a new cut while you're still using the knife tool here's a new one it's the control key and the control key if you hold it down it turns on mid point snap and if you let go of the control key on your keyboard it turns off midpoint snap what does that mean well i'm going to go ahead and press the ctrl key on my keyboard and hover over the edges of this cube in edit mode you can see it snaps no matter where i have my mouse cursor a point to the middle of that edge so i'm going to go ahead and click there i'm going to keep holding ctrl and i'll click there and then i'll press enter on my keyboard and you can see i've cut the top face of this cube perfectly in half let's go ahead and press the k key again to keep going through those little keyboard shortcuts the control key of course is midpoint snap the shift key will ignore snap so if you want to create a new point or a vertex near an edge you see how when i move my mouse cursor it snaps to an edge well if i don't want that if i want to make a point that's right near an edge i can simply hold the shift key on my keyboard and now it won't snap to an edge so i can create you know a cut that's very near an edge and i can press enter of course it's not going to let me put an edge in the middle of the face so it connected both of my ends up to the nearest corners okay pressing k again to go through the rest of those keyboard shortcuts c is the angle constraint keyboard shortcut so if i press the letter c on my keyboard well i've turned angle constraint on so if i start making a cut you can see i'll just click off to the side that it's constraining my cuts to 45 degree angles and these angles are based on my current view in my 3d viewport so because i'm looking at my scene from a random user perspective view it's going to cut and if i cut all the way across my mesh yes you can start off the mesh and go across and click it's going to cut at 45 degrees based on my view and i can press enter and if i orbit my scene you can see well now it's no longer at 45 degrees compared to my view but it was just a moment ago so if you're going to use the angle constraint option you might want to go to a top or front or side or bottom view to look at your scene first before you start making that cut of course you can use your number pad keys on your keyboard or i could press this little minus y uh button on my little gizmo axis up here to go to my front orthographic view if you're not in orthographic you can press this button right here it toggles between perspective and orthographic orthographic means flat and so now if i press the letter k key on my keyboard and then i tap the c key to turn on angle constraint now i can cut directly across and press enter and i know that edge is flat with my ground because i use angle constraint the last keyboard shortcut is really powerful it lets me cut all the way through my mesh it's letter z on my keyboard if i tap k to go into my knife tool you can see the z key is called cut through if i tap z i can now cut through my mesh and press enter and you can see if i orbit around it actually cut all the way through my mesh including faces that i couldn't see before from that angle and so now i have a cut a loop cut essentially all the way through my mesh by the way if you want to do that with the active knife tool here that option is called occlude geometry it's turned on by default so you don't cut through all the way through a mesh it only cuts the faces you can see so it ends right there and right there the color i just made i'm going to go ahead and undo that if i have occluded geometry turned off and i cut all the way through and i press enter well you can see now it goes all the way around based on the view or angle of my view that i was at just a moment ago this knife tools cut through option along with the angle constraint option can be a real life saver if you ever run into a problem where you're trying to do a loop cut through a mesh or around a mesh object and you can't because of n-gons let me show you what i mean if i go ahead and press the letter k on my keyboard to go into my knife tool and i'm going to hold the ctrl key on my keyboard and make a cut across the top of this cube from the middle over here with the control key to the middle over here i'll go ahead and press enter i'm going to turn my little cube into a very simple little house now if i want to later add a door to the front of my house here well i'm probably going to want to extrude a door inward a rectangle inward so i might want to make a loop cut around my house so that i'm forming the top edge of my door so if i go ahead and press ctrl r on my keyboard control r brings up my loop cut and slide tool you can see i can hover my mouse over the mesh and you can see from some directions of this loop cut tool it goes all the way around the mesh like it should but in some directions it doesn't and that's because i'll go ahead and press escape on my keyboard that's because i have a face here and a face here that are n-gons they are faces with more than four sides you can see one two three four five so this face kind of interrupts loop cuts because when you make a loop cut around a mesh it needs to know the exact opposing edge to start at and to go to and if i make a loop cut from there to there well it doesn't know on this face if this cut here should go from that point over to this point or up to this point because there's no immediate opposing edge at least as far as it's concerned so how do i make a loop cut around my house well i could use the knife tool i'll go back and press escape i'll go back to my selection tool i'll press letter k on my keyboard i want to make a cut that goes across my house perfectly flat so actually i'm going to go to my front view i'm going to press the little minus y button up here actually i'll go to my side view so i'll press the letter x here now i'm in my right orthographic view what i want to do here is i want to make a cut all the way through my house but straight across perfectly so i'm going to press letter k to use my knife tool i'm going to turn on angle constraint with letter c of tap c so it's on i'm going to turn on cut through as well so i'll tap z on my keyboard so now angle constraint and cut through are both on and so now if i click over here i can then move my house across and click over here and now if i press enter on my keyboard and zoom out and orbit around you can see it's made a loop cut essentially all the way around my house and i could use my selection tool in edge select mode and i could select i'll hold alt on my keyboard and click on an edge there to select the entire edge loop alt and click select an edge loop on edge and so now i can use the move tool and move that edge loop down to wherever i want the top of the roof to be so as you can see the knife tool can be a great problem solving tool especially when you want blender to make a topology that means an organization of faces and edges on the surface of a mesh that it's not giving you by default so that's the knife tool the second tool i'll be showing you in this video is called the bisect tool and the bisect tool is actually a tool on your toolbar i'll go ahead with this uv sphere selected and i'll make my toolbar a little bit wider so we can see all the tools it's actually hiding behind the knife tool here so if i click and hold on the knife tool icon and i hold you can see i have the knife tool and the bisect tool and you can tell if i let go on it that it looks like a tool you can use to chop off part of a mesh and that's pretty much what it is except it's a bit more powerful than that so let's go ahead and check out how you use it for this i'm using a uv sphere just to mix things up a little bit if i use the bisect tool what i want to do here is start off the edge of the mesh and click and drag across the mesh and if i keep holding down i can adjust where the mesh will be cut across so if i move my mouse around and then i let go it's made a cut not just across my mesh where i can see it's actually made a loop cut essentially around my mesh wherever i defined it and it's giving me this funny looking little gizmo this gizmo on my screen by the way a gizmo is basically any control and blender on your screen lets you move where that cut is now if you go down to this little pop over you can see under the bisect pop over that you can adjust its plane so where it is you can adjust kind of its location you can adjust its normal the plane normal which is basically its rotation in any of the three axes like that you can select clear inner or clear outer clear outer basically gets rid of the mesh that is where this gizmo arrow is pointing and you can select clear inner which will get rid of below where that surface of the arrow is pointing if you select one of the clear outers or clear inners and also select fill i'll select clear outer and fill it will make the new face of the cut into a solid face an end gone in this case so now you can see i've used this tool the bicep tool to cut off part of the mesh now you're probably thinking to yourself hey couldn't you just do this with a knife tool yes you probably could but probably in a few more steps than with the bisect tool so this just makes it a little bit easier to do well this process with a knife tool of course you could make a cut across the mesh you could make that cut cut through all the way through the mesh and then you could delete part of the mesh and you could fill in the gap on the new side of the mesh but this just makes it much quicker with this bicep tool though you can also cut a mesh into two separate meshes with a few extra steps so i'll go ahead and do that i'll press ctrl z on my keyboard to get rid of that bisect cut and i'll use my bisect tool by the way if you don't want to use this active tool you can go up to the mesh menu and it is right here i believe there is no keyboard shortcut for it though like the k key for the knife bisect doesn't have that so if i select the bisect tool it works the same way i can click and drag and i can let go and because i already had used this tool and set these two options it did those for me automatically of course i could adjust you know where the normal is i could adjust the angle of it i believe in some way i believe it starts your cut up here so it bases the rotation of the plane normal uh up here instead of in the middle of your cut or mesh object that's okay but what i'm going to do here instead of clearing either the inner or the outer i'm just going to fill in and create a face uh in the middle of that new edge loop that's cut all the way through my mesh and now i'm going to actually select one half or the other so i'm going to go up to the select menu i still have that new edge loop selected i'll go up to the select menu and i'm going to go to select loops under select loops i'm going to select select loop inner region and what i have to do before i do anything else you can see i was expecting it to select either one half or the other i actually have to select down here select bigger and it'll select the i guess it's the bigger half of your mesh object if you want to separate the other half of the mesh you could always go up to select and invert that's up to you i'm going to select invert again to select that original bigger half and now if i want to separate this mesh or this part of the mesh into a separate mesh to create two halves where i use my bisect tool i can press letter p on my keyboard p brings up the separate menu and i can simply separate the selection here so i'll click on selection and now i have a separate mesh object for my bottom half i'm still in edit mode of the top half so i'll press tab on my keyboard or use the mode menu so now i have a mesh object there i'll go ahead and press g on my keyboard and click to move it up and i have a mesh object here so two separate mesh objects now because i use that fill option with my bisect tool you can see the bottom half in my case has that filled big n gone face there if i press tab to go into this mesh object's edit mode there is in fact an n-gone here if i press tab and orbit around you can see there's a gap or a hole in the mesh there is no filled side there that's a pretty easy fix i'm gonna go ahead and just grab that and move a little bit farther away if i press tab to go into edit mode of this top mesh and i use the edge select tool and i hold the alt key on my keyboard and click on one of the edges around the hole you can see hey is selected well in my case all of the edges around the hole and i can simply press the letter f on my keyboard to create a new face or to fill around those edges or in those edges okay so that's the f key to fill and i'll press tab to go back into object mode and now i have two halves of cut through my mesh now one last thing is of course that i have these origins these little orange dots here and on this mesh object here and usually origins are in the middle of a mesh unless you specify them to be somewhere else in my case i want to move these origins the middle of the mesh because when you use one of the transform tools the move rotate or scale tools the little handles for those tools gizmos they will be coming off of that origin so this looks a little bit weird it really should be in the middle of the mesh so i'm going to select that mesh go up to the object menu and set origin to geometry and that will put that little orange dot in the middle of that selected mesh's geometry so if i click on that you can see it jumps up to right there and now my gizmo handles a little bit easier to understand i'll select this one object set origin to geometry there we go so now i have two mesh objects out of one using the bisect tool so that will be it for this video if you made it to this point in this video thank you so much for watching again my name is colin and of course if you like this video or if you learned something in it please go ahead and click on that like button below this video it really helps out me and my channel and gets these videos more seen of course if you want to see more videos like this one in blender or in the godot game engine go ahead and click subscribe and that bell icon so notified whenever i upload a new tutorial check out my facebook and instagram pages in those two places i post sneak peeks and previews of what i'm working on next and that's where i communicate with all of you the most except here on youtube of course but that'll be it for this one thank you so much again for watching i'll see the next one bye [Music] you

Channel: BornCG

Views: 44,034

Keywords: Blender, tutorial, lesson, 3D, model, modeling, modelling, beginner, knife, bisect, cut, draw, edge, nife, edit

Id: HMg8ezK-Gfw

Length: 21min 47sec (1307 seconds)

Published: Sun Oct 24 2021