Modeling Diving Knife Tutorial
STEP 2 – BLADE
Ok, now we got our blueprints set up the way we want, and now we’re gonna speed things up a bit. Basically all you need to do is to trace the outlines of the blade. Use Line (or PolyLine) and Ortho for straight lines, use Curve for curves, and Match to match the curves to other lines or curves to get smooth transition between them. Usually Tangency is enough option in Match command. For the little circular blades on top of the blade use two circles with various radii. And with Trim just trim the lines you don’t need.
It was easy to say it, but lets get on it and make it. And for your convenience you can put the PictureFrame into another layer and lock it. So when you move or select or perform any other action you don’t mess with the blueprints.

Basic lines & curves
So, as you can see, in the picture above, there are just simple lines and curves. For the lines, make sure you use Ortho so they are straight, either vertically or horizontally. So, naturally next step would be to
Trim some lines. You can hide the middle line, we don’t need it anymore. Ok, now we have some lines and some curves. To you they might seem to be ok, because I did make them pretty accurate. But not 100% accurate. we need our curves to be tangent to our lines. We can adjust that with
Match command. Now, the important thing is to note that once you are in the
Match command it asks you first for the line or curve that will be edited to match the
Match settings (Position, Tangent or Curvature) and then for the curve that you will NOT change with
Match command. Of course there is one option in
Match command that lets you change both curves (Average Curves) but we’ll get to that when creating the handle.
Repeat this for other two.After matching all the curves to the lines, we will need to
Split two lines:

split lines
Now, create a
Point on the Mid point of the little line you created by splitting the top straight line. Once you create the line, move it up by units. This
Point will be the center of
Circle.

point
Ok, now create a
Circle with 10 units as radius and as center use the point.

circle
Now, guess what, we are going to
Trim that circle with the line and
Mirror it using the line we recently hid to make the copy on the bottom side as well.

curves and lines for planar surface
Before we go and create our first surface, we need to join the curves. Select all the lines and curves like on the image above, and
Join them. Next thing we need to do just before creating surfaces is move the lines we just joined. From the blueprints we can see that the thickness of the blade is 5 units. Since we started everything from the origin (0,0) we already have set up mirror plane. We can just make one half, and then
Mirror it to the other side as well.
Using
Line command create one
Line like on the image below, and using Copy command copy it 3 more times. Using End OSnap option will do the trick.

Four lines
Create one more
Line:

Another line
Do the same for bottom with
Mirror or create a
Line again. Now, using
PointsOn turn on the control points of the left horizontal curve. And move the last control point to the end of the inner tip of the flat closed set of lines and curves:

Points On
Now, from top viewport (it would be smart to disable OSnap for the moment) adjust other control points so the curve gets the smooth arched direction:

Adjust control points
After you adjust the remaining control points, you can enable your OSnap now, and using
PointsOff command hide the control points. Now, go ahead and create your first surface. Using PlanarSrf command create a surface out of closed set of curves:

Planar surface
Using
Explode command explode the closed curve set you just used to create this planar surface. And, then using
Join command join these curves only:

Two sets of joined curves
I’ve created this line with
Line (or PolyLine) command starting from the top corner and moved it down to be perpendicular on the edge of surface (or curve). Use Perp in OSnap.

line
Ok, now with
Sweep2 command we will use upper and lower sets of curves as rails (yellow), and three section curves as sections (red):
Now, lets set some curves for the lower part of the blade. First we need to
Join 4 curves into 2 curves:

Two joined curves
Again, using
Sweep2 command, create a surface:
Now, using PlanarSrf we will fill in the two gaps we have left. Then we will extrude this set of two lines and one curve with
ExtrudeCrv command.

Extrude
For the extrusion height you can type in 2.5 or just use any of the lines as reference points:

Extrusion
Do the same for the other side, or just
Mirror it. Now, using
SrfPt command fill the side of the blade:
Ok, now
Join every surface. Then
Mirror that polysurface and
Join those two halves. Now, we have our blade form on which we will proceed with modeling details.

Base blade surface
Using
Line command, create a line on top of the blade edge.
But try not to snap to the left end, but rather finish the line a bit closer to the corner:

Closeup
Next thing we’ll do is
Divide the line into 7 parts. The command
Divide isn’t actually splitting the line into 7 separate parts, but it places Points on the line instead.
So, using the second point looking from the left we will
Split this
Line:
Ok, now we need our blueprints again. You can turn on the layer you put your
PictureFrame in on. Using
Arc command, make sure you click on the StartPoint option in the command line, and then click on two points:

Click on Radius to input the radius
Now, like on the picture above, click on the Radius in the command line, and input number 6 as radius. After that click on the viewport (Front) to set the direction of this arc.
Make another
Arc with 8 units as radius, and using Copy command copy those two arcs 6 more times:

Copy arcs
Now, using the bigger ones (stay in this viewport – just set it to Ghosted by right clicking the Front caption)
Trim the blade surface:

Trim surface with bigger arcs
Now, using
Loft command make a surface between two edges and one smaller arc:
Repeat this step for all other six arcs, or just Copy this surface six more times:

Final blades
Next, just
Join all surfaces. And for the last thing in this step we will use the same method on the bottom blade. So, first using blueprints, trace the outlines with
InterpCrv command. Adjust the curves with
PointsOn command if needed.

Some more curves
Before we start trimming the surface, we need to trim our smaller curve with the surface.
Now, using bigger curve we will trim the surface:

Trimmed surface
Now, adjust the smaller curve’s ends. With
PointsOn command we will show the control points and move each end to the end of the surface:

Adjust curve
After that we need to hide the control points with
PointsOff command. Now, again, with
Loft command make a surface: (it might be necessary to do one side at the time and then
Join both)

Final step on the blade
Related posts
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AWESOME tutorial! Haven’t seen any other tutorials with this much detail!
thanks Brian, I appreciate it
Looks a lot like Ragde’s diving knife.
It is. If it is “his” design.
I’m not really teaching design here, rather just modeling in Rhino.
What dimensions do you use and what version of rhino is this?
I used centimeters, but those measures aren’t absolutely accurate, just a reference. Rhino version is v4.0 for all tutorials on this site.
is it possible to use background bitmap instead of pictureframe? for some reason pictureframe just draws a frame and there is no image. do you know why?
sure is. you can use background bitmap. As for the image not showing in pictureframe, search the forum, there have been couple of similar questions. I’d guess it might be problem with drivers. But than again, I might be wrong.
Excelent tutorial. Thank you!
Great tutorial but i have some trouble with the first sweep 2 rail for handle. i get some strange surface result. may i send you an image by email to check what is the problem?
thanks in advance
go to http://www.rhino3dhelp.com/forum/index.php?board=11.0 and open a new thread with your image attached.
first of all thank you for this awesome tutorial..,, second is to cast a newbie question.. how can I view the image after I make a picture frame?? it seems no bitmap image or jpeg Appeared after the operation…pls…help… if I’m going to use background image it will appear ,but if I;m going to use picture frame it won’t appear. only a rectangular line appeared….. as this tutorial instructed is much easy to use picture frame than background image….. pls…help….Much appriciated your help and respect..
regards