Perfect Threads

ZooHead

Well-known member
Sheetrock Screws. I don't know if there are other names for this type of screw
in other parts of the world as Sheetrock may be an American brand name.

Sheetrock screws usually have a black non reflective finish.

The tip is a problem area where so many points come together, it makes using the Optimize tool hazardous.

I wanted to build one without Subdividing, but the Wrap Modifier Extrude Creator sections limit is 20 and I needed 64.
So I had to find other ways much too tedious to explain, but I'll figure a simpler method. Correction added

This one looks great but it's not watertight at the tip due to the Optimize Tool making some holes.

Sheetrock Screw Tip.jpg
 
Last edited:

Chris Heath

Member
Thanks so much for this thread :ROFLMAO:.

No really, I just tried the wrap modifier method and it worked! I need to do more with modifiers. The helical steps above are the next thing to try.
 

Chris Heath

Member
Here's a four part tutorial that should illustrate the steps.



View attachment 37230
Thanks so much for this Eric. I got to the end of Part 2 and it looks identical to your last step in Part 2 by using Cover and Normal Move. The Normal Move only moved the selected polygons away or towards the centre. But Part 3 starts with the tapered thread. So how do you go from the the last image in Part 2, to the first image of Part 3? I had some success by loop selecting the edges and 'normal moving' them, but there are some differences between what I'm getting and Part 3's starting point.
 

ZooHead

Well-known member
Thanks so much for this Eric. I got to the end of Part 2 and it looks identical to your last step in Part 2 by using Cover and Normal Move. The Normal Move only moved the selected polygons away or towards the centre. But Part 3 starts with the tapered thread. So how do you go from the the last image in Part 2, to the first image of Part 3? I had some success by loop selecting the edges and 'normal moving' them, but there are some differences between what I'm getting and Part 3's starting point.
Looks like I left out a step. Once you Cover and Normal move use Normal Scale to get the taper.
Sorry for that and thanks for pointing it out, I'll have to fix that.
 
Last edited:

ZooHead

Well-known member
Polygon count comparison between a subdivided and a non subdivided screw.

I really want to see difference between the two, and also a subdivided model manually optimized.

Parameters: 1 unit long, 0.1 shaft diameter, TPU 16, P= .0625 (P is peak to peak)

First I had to make one with no subdiv. I can't use the Spline Extrude
method because the Extrude Creator can only make 20 sections and I need 64.

With my original "Plane" method I used a 1x1 plane but for 64 sections I chose to double the width.
If you double the width, you divide the .0625 by two for the Move setting in the Wrap Modifier.

Hi Res.jpg


Hi Res 01.jpg
 

ZooHead

Well-known member
Here's a comparison of the polygon count.
It's unexpected but there is a distinct difference in the reflection for some reason. :unsure:

Rendered side by side with the same material.

Poly Count.jpg
 

MonkeyT

Active member
The difference in the reflection is very interesting. I'm not sure there's a way to 'fix' it in the low-poly model, but could you mimic the issue by applying a higher Smooth setting in the high-poly model? That may identify the nature of the issue.
 

ZooHead

Well-known member
@MonkeyT Thanks for the suggestion, it did give me a better edge reflection, but it still looks so different.
I like the way the SubDiv model looks but radially they are the same. Vertically the SubDiv model is more dense.

Poly Count Smooth.jpg
 

ZooHead

Well-known member
I did some more test with two straight cylinders and straight but spiral Wrapped cylinders.
These all do not show the differing reflective quality.
It's only with the threads present that this occurs.
 

MonkeyT

Active member
Question: "Smoothing" doesn't literally deform the polygons, does it? It's a purely rendering thing that wouldn't affect a model's shape against the rest of the layout, right?

My guess is Smoothing on the screw model is acting as if the boundary between the cylinder and the threads is getting pushed out at the top and the bottom so that the thread walls become a slightly concave, letting it pick up that hot highlight from the top of the environment and the darker coloring at the bottom. What it doesn't do, however, its actually bend the boundaries of the polygons seen in profile, meaning the "outside" edges of the object are "clipped" as sharp as they would normally be, keeping the threads' points and corners sharp in its profile. I think it's like drawing and filling a square selection in Photoshop, using it to great a mask layer but only blending the image, not the mask. You get a softer texture inside the square and half of the softened edges, but they are clipped by the hard-edged mask.
 

ZooHead

Well-known member
Smoothing is just for shading, like a reverse bump map, so no polygons change.
Well they both look good so no real problem, it's always something.
 

MonkeyT

Active member
Beautiful. I think breaking the cylinder's polygons from two into four (vertically) between each thread did the trick.
 

ZooHead

Well-known member
One thing about the Wrap Modifier I haven't covered,
it builds a cylinder from the edge, not the center.

This means you need to establish a central point eventually.

Don't just use Center Pivot Point, that won't do it.
You have to move it manually in Pivot Mode, and then Burn Pivot Point.

First I move the model over the World Center, then move the pivot point to the World Center.

Making the screw tip:

tip_fill.gif
 
Top