Hi all, this is an offshoot from the No.1 Pocket Kodak thread, I thought I'd put up this topic to the community to find a simple and efficient way to model a knurl pattern on a cylinder, like on a thumb screw produced on a lathe. Inspired by Pilou.



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The game's rule is ovoid numerous boolean operations who can slow down the system! ;)
Here an "helix": Array Circular with vertical step, Array Dir)
Boolean>Array>Array etc...
So just one boolean inside the first component ;)
The only difficulty is find the first component ;)
After it's very speedy and no problem of boolean!

Concept :)
Rotation is given by the input angle

That looks cool and dangerous Pilou :), I went for the more traditional look, thanks for getting me to have another look at this, it was worth it.
The steps are in the zip file.




Cheers

And here are a couple more!
I think Knurl A is probably closer to one on a lathe.

Brian

Cool ideas here! Just a note - things like this with a kind of repetitive small scale detail pattern can sometimes be most convenient when applied as a rendering-time operation instead of modeled explicitly. Stuff like texture mapping with displacement...

It definitely looks really nice when modeled directly as well, but that also adds a considerable amount of complexity and weight to the model.

- Michael

I suppose it's planned with the layer system, but be able to change the display detail level per object/layer would be welcome for this kind of work too.
This kind of details in nurbs is really heavy, but the exported geometry can be really light with the right settings in the meshing (hyperthreaded :o)) tool.

Displacement map can give great results, with the right engine ... but not that many renderer can do good (and fast) displacement map out of the box . The setuping time can be long too .... displace baking, probably normal map baking if the engine can't do microdisplacement map (like lightwave :'( ) or native 3dsmax). Without saying some uv's seams fighting ... all in all I often prefer to build the detail in the model too.

A bit rough perhaps but please feel free to use if of help.

Brian

Hi PaQ,

> I suppose it's planned with the layer system, but be able to
> change the display detail level per object/layer would be
> welcome for this kind of work too.

I'm kind of hoping to get that solved by having a kind of automatic "down shift" type system for lowering detail on small parts without having to mess around with settings for it.

Some kind of manual control could be useful, but pretty labor intensive in many situations like if you import a highly detailed existing CAD model through STEP or IGES formats, you probably don't want to spend an hour setting custom detail properties on all the little bits of it to get it to a more manageable level.

It kind of needs to happen more automatically for it to help out in a wider number of situations.

NURBS models made up of a ton of little tiny surface fragments will tend to be rather heavy in many aspects though, things like trim curves on a NURBS model have both a 3D curve and a UV curve for every segment in the trim boundary. That kind of goes along with the whole ability to have an "underlying surface".

A polygon mesh object has less overhead per polygon than that. Of course the nice thing with the NURBS structure is that each surface is an actual curved surface and not just a flat polygon, so one surface in the NURBS model under normal circumstances covers a larger area, like as you know a sphere can be just one surface in a NURBS model instead of a whole bunch of polygons to approximate it.

- Michael

>>

I'm kind of hoping to get that solved by having a kind of automatic "down shift" type system for lowering detail on small parts without having to mess around with settings for it.

Hi Michael, that sounds really cool for micro fillets addict :)

This is probably a better quality file for using in a displacement render.

Brian

I tend to like to model everything unless it like a brushed/anisotropic surface. When trying displacement like this you would need to up the sub-d level to a fairly high level well beyond the amount of polys used to just model it in the first place. Dantas example above only outputs around 2500 polys so that is light for the affect it is achieving. To try and get the same look with displacement the poly count would end up much higher.

Also you have the issue of moving between applications. If it's all modeled then no problem but with displacement each app has to be tweeked a little bit to achieve the same appearance.

Is this a secret?
(Grendel--your message noted--at times displacement is helpfull)

Anyway, taking a file into a 3D programme and setting it up to produce an image that can be useful as a displacement map is pretty painful..

A solution, with MoI, because the default lighting is perfect, is to just do a screengrab and trim/save that image as your end result.

Hope this image shows the simplicity.

Brian

I think a scaling detail function would be ideal (beyond meshing angles), automation of this function may be very complex, however I have seen it achieved with polygons (e.g. Torque game engine demo, this is much like the meshing angle option I suspect). Maybe a filter that looked for all surfaces below a set size (area) at each detail level, but replacing them with a different geometry (some sort of interpolation) may require more processing than display of the original. Perhaps a simple show/hide functionality, my only concern is that this approach would drive the desire to model extra (simplified) surfaces. I think this is a tough one, I cannot, off the top of my head think of a good way to do the math to achieve this on a nurbs model, especially since there are so many distinct ways of generating features on solid models these days (yay for that). But, I'm always available to bounce ideas off of. Maybe a simple elimination of vertices that are co-located within a set 'mesh' (for lack of a better theoretical term) size, but this may not give the desired result in all cases, and surfaces would be recalculated each time the 'mesh' was re-scaled.

Adam.

Hi Adam, a lot of cool ideas in there!

But yeah some of what you describe in there would be quite difficult to achieve and would take a lot of time to implement. I'm just not going to have very much time to spend on this so my primary target is going to be something simple like using a much coarser angle metric on small pieces.

Just that by itself should give a pretty significant reduction to memory consumption for complex models with a lot of little pieces and little fillets in them.

- Michael

Hi Brian,

That way of doing displacement map is not good at all and you will just have something that more less look like the original details.
To capture the details you need to generate a 16 bits (at least) grayscale image of the elevation, and it's something different than screengrab a top lighted model.

A normal map will give you a much better result too, but also requiere using some extra tools, like xnormal
http://www.xnormal.net/2.aspx

Cheers

Paq
Is this grayscale image any different?

Producing a normal map with the ,free, Nividia filter plug in for Photoshop is a piece of cake anyway--though I also have a normal plugin in Carrara as well.

In most instances, I have no problems with any of the three file types in the Carrara Displacement tag as far as I can tell. Maybe problems with different apps?

I thought that the Carrara image showed that the screen grab from MoI worked--despite the "theory"?

Brian

PaQ

As a follow up. (Maybe my apps are different)

I can get good 3D displacement either with colour images or b&w or normal maps.

Or NO images at all! --see attached

Brian

Hi Brian,

Just to let you know that you have an overlapping situation in your displacement map (circled) and if you use it over a large area it will show up like dogs you know what :)

Ha! You picked it!

There were two, but the other one was ouside the screen save.
Old blokes, when it's late, take shortcuts rather than go back--OFTEN!

But it was good learning all the same.

Brian