How to Use the KNIFE Tool in Blender!

what's up guys Justin here with the CG essentials.com so in today's video we're going to talk about how to use the knife tool in blender let's go ahead and just jump into it alright so the way the knife tool works is you can tab into edit mode with an object selected and then you can tap the K key in order to activate the knife tool or you can just click on it right here okay so notice how when I activate that tool this is highlighting different parts of my model to show me where it would cut this object and so basically the way this works is let's say that I was to click on this point right here and then move my mouse down here and click on this point right here notice how I'm getting a little inferencing to the different points in here that's actually really helpful for making sure that we cut things the way that we want but notice how when I click notice how what that's going to do is that's going to add an extra Edge in here and it's going to split this face up inside a blender so now if I hit the enter key I can finalize that cut and so now notice how this is split this object into two surfaces one thing to note about this is it is really easy to create ingons by doing this so just be aware that if you do create n-gons in here notice how now if I do like a control r or anything that requires quads that's going to be broken on this side of the face so just be aware of the geometry that you're creating sometimes those in-gons can be problematic but a lot of the time this can just make life a whole lot easier but a lot of the time we don't necessarily really care all that much it just kind of depends on what we're trying to create you just need to be a little bit careful with this but notice how for example now I can take those surfaces that I've created and I can extrude them because they're completely new surfaces and so notice how when you have the knife tool active it's set up where it's going to add an additional point on your cutting path every time you click right so if I click in here like this what it's going to do is it's going to add a new point until I close it and then I'm going to hit the enter key right here and notice how it does add a little a bit of additional supporting geometry in here right here but now I could take this scale it in something like that and so if you ever have a cut going and you want to cancel it like this you can just hit the Escape key and it's going to go away so you're not necessarily locked into those there's a number of different keyboard shortcuts that go with this tool actually so if I hold the shift key down notice what this is going to do is this is going to lock this into midpoint mode so it's snapping to the midpoints of these edges so if you hold the shift key you can find the midpoints of things and use those as your snapping locations and notice how you can cut across an entire object based on your view as well so if I single click move my mouse and then click again notice how it's going to split this object based on my view in a straight line like this and so you can use that along with your camera location in order to add Cuts based on your view I don't do that very often mo more likely most of what I'm going to do is going to be in like the straight on view like this so I can make sure that I'm only cutting this front face right here and so one thing to note about this tool is when you tap the K key you can also tap the a key in order to set an angle constraint and what that means is that means that your object is only going to or your cut is only going to be constrained by the angle that you have in here so if I was to type in a value of 45 degrees with this active so I'm going to click on this point tap the a key and tap in 45 notice how that's going to set this to a 45 degree snap if I was to type in 15 it's going to do a 15 degree snap just like this so you can use this in order to set your cuts based on an angle direction if you want to do that and so one other thing to be aware of is there's also an option here for cut through and so what that means is that means that right now for example let's say that I was to just make a cut like this right what it's going to do is it's going to cut the geometry that I can see however if I was to tap the K key and then tap C of in order to go to cut through mode notice how now when I move my mouse you can kind of see some additional points in here that means that what this is doing is this is cutting through the entire object whether you can see it or not so for example if I was to click on this surface right here with cut through mode active notice what that does is that cuts all the way through my object like this and so that can be really valuable for a lot of things but what it really does is it gives you the ability to slice your entire object so let's say you wanted to slice this all the way through you would just want to make sure that you tap C in order to be in cut through mode like this in order to do that and so you can also display distance and angle measurements by tapping the S key so notice how if I tap s in here what that's going to do is that's going to allow me to toggle lengths as well as angles on my surfaces so notice if I tap it a couple different times it's going to show me different things right if I tap the S key it's going to show me just the length if I tap it again it's going to show me just the angle so you can use this in order to see the lengths of the cuts that you're making note that your standard inference snapping is going to work as well so if I tap the X Y or Z Keys notice what it's going to do is it's going to lock to those different axes like this so note that you can also cut multiple objects at once if you have them selected when you go into edit mode so for example if I wanted to slice across all of these spheres like this I could just do a shift click to select them all and I can tap into edit mode and notice how when I jump into edit mode it's going to allow me to edit all of these objects and so let's say I wanted to cut across all of these objects I just tap the K key well notice how because they're all all selected I can just click and drag and it's going to allow me to cut through all of them like this so if you do want to cut multiple objects like this you can do that just by selecting all of those objects inside of edit mode one thing to note about this is note that it only cut through the visible geometry so if you wanted to cut this across the whole object right you would probably want to with the knife tool active tap that c key in order to activate cut through mode like this and so notice how then these cuts are going all the way across the object like this and note that there is another tool in here called the bisect tool and basically what it's designed to do is it's designed to help you cut through the full object one thing to note about this tool by the way is you want to make sure that whatever you want to cut through you've selected so I'm going to tap the a key before I do this but with the bisect tool what I can do is I can click and drag in here like this and what it's going to do is it's going to give me this little plane and I can use this plane in order to set where the bisection of the object is notice how I can orbit while I do that but I can use this in order to adjust the cut that I'm generating in here but where this gets really powerful is not only does it have the ability to do that you can also use it to remove everything in front of or behind that point that you're creating or that plane that you're creating so notice how you can use it to slice this object I can also use it to add a fill wherever this object is being sliced like this so the bisect tool in my opinion is probably the better tool for like cutting all the way through an object so it's very powerful for that press well you do have to be really careful of your topology when you use this tool it can be really helpful for cutting out different parts of objects other things like that so leave a comment below let me know if you have any questions about the knife tool as always thank you so much for taking the time to watch this and I'll catch you in the next video thanks

Channel: The CG Essentials

Views: 23,917

Keywords: blender, blender 2.82, blender 2.8, blender modifier tutorials, blender tool tutorial, the blender essentials, the cg essentials, thecgessentials.com, justin geis, justin geis blender, blender 2.9, blender 2.91, blender knife tool, blender knife tool tutorial, blender knife tutorial, blender knife edit mode

Id: fb3qod9-9DM

Length: 7min 30sec (450 seconds)

Published: Tue Dec 13 2022