For those who don’t know what a ‘Frustum’ is, it’s basically just a cone, with the tip of it chopped off basically.
So I’m trying to create something similar to the image below. However, I tried using a Cone Mesh part and to negate the tip off, but can’t use CSG on MeshPart’s so scrapped that idea. Does anyone have a simple solution?
You could either make a cone union by negating tilted blocks around the cylinder and then chopping the top off, or you could just make that mesh yourself in 3D program like Blender.
This is how I’ve done it using unions:
First, I made a part adjacent to the cylinder, then cloned, rotated it by 180 degrees and moved it to the other side. Then I duplicated those 2 parts for every 15 degrees around the cylinder. Then I changed Z rotation to 15 on all those parts through properties, and got this:
Then I got a cone with a weird top, and I just simply negated the top.
And in the end I got this:
Obviously could be made smoother using larger amount of parts and less rotation increment.
I remember seeing another diagram example of this here if that helps you figure it out. The diagram is a bit better and also offers the mathematics behind it.
Making shapes like these is incredibly easy and efficient in Blender. Here’s a quick guide on how to do it.
The first thing we have to do is insert a primitive cone in the viewport. To do this, we press Shift+A and select the Cone.in the Mesh category.
You may notice that the cone is too wide for what we want to make, so to fix that, we press S to scale, then press Shift+Z to exclude the Z axis, then proceed to make it thinner. After you’ve done that, press Ctrl+A and apply the Scale. This will prevent bevels from messing up later on.
Next up, we need to cut off the top. To do this, we press Tab to go into edit mode. Press Ctrl+Tab+1 to change the select mode to Vertex. Pick the vertex on top of the cone, press Ctrl+Shift+B and drag it out.
In the image you showed us you can see that the top of the cone has a little bevel. To do this, we press Ctrl+Tab+3 to swap to Face select mode, select the top face, and press Ctrl+B to bevel the edges.
To top it off, we go back to object mode by pressing Tab, go to the left panel and change Shading to Smooth. Then we just apply an edge split modifier and presto!
If we want to get even saucier, we can go back to our CSG roots and use a cylinder combined with a Boolean modifier to cut a hole through our cone, as well as a little bevel to really get that detail. Be warned though, as this can easily double the poly count in your mesh,
Once you’re done with all that, you can put them all in place.
Following all steps, excluding the Boolean process, should take roughly 20 seconds. You should also take these things into account.
If you’re going to put a lot of these in your game, keep an eye on the poly count. Small props don’t need a lot of detail, so you can probably get away with halving the amount of sides the cone has. The difference is noticable but it’s not that bad.
If you never see the bottom of the cone, remove the bottom face. That’ll get rid of most of the unnecessary polys.
If you’d be interested in a video tutorial instead, let me know and i’ll make one in a bit.
An easy solution to making a cone is to take two wedges arranged to form a rectangular prism. Then revolve them using Archimedes 2. And then union it all.
Diesoft gives an elaborate explanation on the simple tricks you can use with basic studio shapes to form complex structures. Definitely worth a watch.
When I make a boolean modifier like that some faces can turn out missing or “deformed”, especially in more complex shapes. Am I just doing it wrong or are they meant to be used in select situations?
And you definitely don’t need to cut the hole out of the cone for that joining rod. You could even just put that detail into a texture if you wanted.
You don’t even need to chop a cone. Just make a cylinder and scale the top cap on the X and Y axes. Done. You can use the boolean process to cut the hole, but you might also consider cutting the holes manually and joining the two resulting edges. Boolean workflow is fast, but the tradeoff is sometimes nasty shading issues in Roblox from n-gons it usually makes, or more accurately from weird normals at the edge vertices after triangulation (if you don’t clean it all up by hand, which is not fast).
Blender’s Boolean modifier is not suitable for cutting with complex geometry. You should always try to stick with the primitive shapes. But even if you do that, it can result in nasty artifacts. That’s why it’s important to take measures before applying the modifier. Here’s an example on how to do that on the Frustrum pillar.
For starters, here we have the pillar, and the cylinder which we will be using to cut the hole in the mesh.
If we were to apply the modifier now, all faces of the cone touching the cylinder would be affected by the modifier. This is an issue, because the faces are way bigger than the cylinder, and it leaves much room for artifacts.
What we need to do it make the zone that the Boolean modifier can affect as small as possible. By using the knife tool, we can add extra edges to isolate the area around the cylinder.
If we put the cylinder back again, we can see that it only touches the highlighted faces. This should heavily reduce any mess it would make.
Now it’s only a matter of enabling smooth shading and adding an edge split modifier. The finished result should look like this.
Now you might be wondering, what would happen if i were to skip all of that and apply the Boolean right away? The result would look like the cone on the left (image below). Compared to the one we made on the right, you can see that it left some nasty shading, and it can get much, much worse on complex models.
This is the workflow i use for making holes and such. Do keep in mind that while it gives nice results, it’s not very suitable for everyday game assets.
It’s true that for standard props it would be overkill to put details on meshes that eat performance and nobody woud notice. I highly prioritize optimization when i create assets for developers and wouldn’t resort to doing this without a valid reason. However, if you were to create a highly detailed showcase to get noticed by EBR senpai, it might just come in handy.
There are many ways to solve a problem. We don’t all eat ice cream the same way, or put our clothes on in the exact same order. In the end, the model will be the same. It all comes down to personal preference.
Manual cutting does not work in the case of the Frustrum pillar. Doing this would give the same result in terms of artifacts as the Boolean modifier on the left cone.
I find that if you take the proper steps before applying the boolean, you can get good results the majority of the time.
Thank you!! That’s very helpful.
Thanks for showing your prep; isolating the area the boolean modifier will influence is indeed key to not letting booleans make a mess of your topology.
