CAD Forum

Hi all,

In the attached part file, I'm trying to make a revolved feature from "SKETCH Base". But the result doesn't come out how I'd expect it to! Take a look at the attached screenshot, and specifically look at the bottom surface.

Anyone have any ideas?? All help is appreciated!

Thanks in advance,

Seem like a correct revolve to me based on the section view
As you are revolving a concave geometry along an axis, the model will look "flat" depending on your view angle But if you look at the section view/ highlight the surface, you will notice it is still following your profile If this is not what you are looking for, you will need to revisit your modelling approach

Zhen-Wei Tee wrote: ↑Sun Jul 25, 2021 1:12 am Seem like a correct revolve to me based on the section view
image.png
As you are revolving a concave geometry along an axis, the model will look "flat" depending on your view angle
image.png
But if you look at the section view/ highlight the surface, you will notice it is still following your profile
image.png

If this is not what you are looking for, you will need to revisit your modelling approach

Very helpful, thank you! I need to re-visit my approach, haha...

Ballfreak10 wrote: ↑Sun Jul 25, 2021 11:33 am Very helpful, thank you! I need to re-visit my approach, haha...

The attached is where I arrived after remaking the sketch. I just don't understand...why does the bottom surface still appear flat??

Ballfreak10 wrote: ↑Sun Jul 25, 2021 11:47 am The attached is where I arrived after remaking the sketch. I just don't understand...why does the bottom surface still appear flat??

Again, this is most probably due to you are having a concave surface as a base...
This is just how concave surface behave, when you project a concave surface, you will get a flat surface, you might be able to distinguish it by adjusting the lightning and viewing the shadow, but i do not recommend it (If you are really interested, search for perception and concave/convex surface, there are several study on that) I rarely deal with concave/convex surface, when normally I will just split the surface to show the "curvature"

It's not behaving as I'd expect either. I played around with it for a while and couldn't figure it out, but I don't do Revolves much. Maybe someone who's more familiar with them can figure it out.

At the centerline of the revolve, the line to create the bottom needs to be tangent to the horizontal. Draw half of the shape you want. I'm not near my SW machine right now, but that's what the problem looks like from here. So at the bottom of the centerline, draw a horizontal construction line, and make the sketch for the bottom of the feature tangent to it. Or if the bottom is supposed to be an arc, make sure the center of the arc is in line with the centerline, at some distance below the rest of the sketch.

Zhen-Wei Tee wrote: ↑Sun Jul 25, 2021 12:59 pm Again, this is most probably due to you are having a concave surface as a base...
This is just how concave surface behave, when you project a concave surface, you will get a flat surface, you might be able to distinguish it by adjusting the lightning and viewing the shadow, but i do not recommend it (If you are really interested, search for perception and concave/convex surface, there are several study on that)
image.png

I rarely deal with concave/convex surface, when normally I will just split the surface to show the "curvature"
image.png

Ok I'll just accept that it's a concave surface even though it looks flat, haha...thanks again!

Zhen-Wei Tee wrote: ↑Sun Jul 25, 2021 12:59 pm I rarely deal with concave/convex surface, when normally I will just split the surface to show the "curvature"

This is a great way to examine it within the part. You can perform multiples of it for additional edges visible, and you can suppress it but keep it for future reference.

You could also play with appearances, lighting, reflectivity, transparency, and such to produce visual effects to distinguish the curvature more clearly.

Another way (merely another idea), much less intuitive when working within Part context, is to place it in a test assembly and begin mating to that surface. Mates available to a flat face are different than those available to a curved face, or likewise even a conical / cylindrical face. In your case, you may mate a sphere component as tangent to the face, and then drag it around to see its position better. Think of it like a marble or a bearing. Also, mate a cube component to the face, and see if Parallel is available or not. For faces, parallel should only be available upon a flat face.

I deal with this aspect when working upon imported STEP files where, for example, a bolt hole that I would expect to be cylindrical is comprised of two apparently hemi-circular faces, neither of which has a measurable radius. Another example is a mounting "foot" surface from imported body which is not even a flat face. In these cases, I will provide a reference entity (axis / plane) to hold a position and to mate to.

Tom G wrote: ↑Mon Jul 26, 2021 2:22 pm You could also play with appearances, lighting, reflectivity, transparency, and such to produce visual effects to distinguish the curvature more clearly.

Tom is onto the right idea with lighting. The "3 Point Faded" scene used in the default templates shipped with Solidworks is embarrassingly terrible for modeling work. In fact, with the exception of studio room 2, which was added more recently, they pretty much all are.

I've illustrated the issue below. Based on where the directional lights are (behind the part) only ambient light can reach your complicated bottom face. Ambient light is a computationally cheap hack to fake true indirect lighting. Without some accompanying direct lighting, it makes everything look flat with no appearance of depth.
If you use sensible direct lighting in combination with a little ambient to keep anywhere from looking too dark, the complicated nature of the bottom surface becomes clear. This is no realview, no textures or fancy face appearances. Just lighting pointing where you need it. And lighting that isn't locked to the model, so it always points where you need it.
I'm no expert in this stuff, so I'm sure there are better scene files out there, but I've attached the scene that I used here as a zip file if you want to play around with it. Add it to a folder on your machine and point your System Options file location for "Custom - Scenes" to that folder.

ryan-feeley wrote: ↑Tue Nov 29, 2022 4:08 am Tom is onto the right idea with lighting. The "3 Point Faded" scene used in the default templates shipped with Solidworks is embarrassingly terrible for modeling work. In fact, with the exception of studio room 2, which was added more recently, they pretty much all are.

I've illustrated the issue below. Based on where the directional lights are (behind the part) only ambient light can reach your complicated bottom face. Ambient light is a computationally cheap hack to fake true indirect lighting. Without some accompanying direct lighting, it makes everything look flat with no appearance of depth.

image.png

If you use sensible direct lighting in combination with a little ambient to keep anywhere from looking too dark, the complicated nature of the bottom surface becomes clear. This is no realview, no textures or fancy face appearances. Just lighting pointing where you need it. And lighting that isn't locked to the model, so it always points where you need it.

image.png

I'm no expert in this stuff, so I'm sure there are better scene files out there, but I've attached the scene that I used here as a zip file if you want to play around with it. Add it to a folder on your machine and point your System Options file location for "Custom - Scenes" to that folder.

This is a great scene! I just tested it out and loaded it into our system.

Things look so much cleaner!!

Thank you for sharing!!

Late to the game, but... Turn on Zebra stripes?

are you trying to show it rendered, or just think that is isn't correct? By using the cross section tool you can see it is the correct shape and that the bottom has a contour. If your wanting to show a rendered part then you really should use Visualize or another rending software, or at least play with the lighting some.

josh wrote: ↑Tue Nov 29, 2022 10:14 am Late to the game, but... Turn on Zebra stripes?

that works I was going to also suggest curvature but that doesn't help because the curvature is uniform.