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@slrove Thanks! Appreciate the kudos and detailed question.

Subdivision sketch: angled cylinder intersections.

Quad grid topology can be important for certain parts of a game art workflow but it's generally going to be acceptable to use some triangles and n-gons to streamline the modeling process. Most in-game assets will need to be triangulated before baking. So there's often little benefit to spending a significant amount of time creating a low poly mesh that's all quads.

Some pure subdivision shapes will have surface quality issues that can be resolved with consistent quad geometry but the root cause of a lot of common subdivision artifacts is shape deformation that's directly related to the modeling process or abrupt changes in the base topology. Whether or not the high poly mesh needs to be all quads, excluding any workflow specific requirements, really just comes down to what the surface looks like when subdivision is applied.

There's generally going to be a couple of different ways to layout the base topology and a few more ways to structure the order of operations used to model the shapes. Which approach makes the most sense often comes down to how the model will be used, technical limitations, project requirements, timeline, etc. but it should be possible to create most hard surface objects using basic poly modeling operations.

Trying to manage all of the support loops, while modeling the shapes individually, tends to create a lot of unnecessary mesh complexity early on. Which can make it difficult to adjust the topology flow or connect adjacent mesh components, without deforming the underlying shapes. It's often much simpler to resolve topology issues at the lowest level possible by using the block out process to create accurate shapes that also define the loop flow.

Redirecting the loop flow

Using the existing edges as support loops and matching the edge segments of the intersecting shapes is generally considered best practice but there are some situations where it's not possible. A common strategy to resolve this type of situation is to match the existing segments wherever possible then cut in additional edges to redirect the loop flow around the shape intersections to produce a mesh that's all quads.

Below is an example of what that process could look like. The arbitrary number of segments in each cylinder limits the segment matching to the slight round over that runs around the edge of the larger cylinder and intersects the base of the smaller, angled cylinder. Additional loop cuts can be used to join the remaining segments around the shape intersection.

This strategy can produce usable results quickly but does tend to have some compromises when it comes to the overall surface quality.

The area around the highlighted quad, where additional loops are used to redirect the flow around the shape and as a workaround for segment matching, has edges that cross over the existing segments in the base shape. This abrupt change in the topology disrupts the spacing and deforms the shape of the curved surface. Which tends to produce a subtle smoothing artifact that's visible when lit or viewed from glancing angles and when using highly reflective material values. The change in topology flow also produces a five sided E pole that's left unsupported in the middle of the shape. While this pole isn't causing any visible artifacts with this material, it does have the potential to cause surface quality issues. Especially if there are fewer segments in the underlying surface.

There's also a visible pinching artifact around the base of the shape intersection, where the loop around the base of the fillet interrupts the segment spacing of the larger cylinder. Manually adjusting the position of the highlighted edges can minimize the visibility of the pinching artifact between the shapes but can reduce the shape accuracy or create other types of smoothing artifacts. Expanding the fillet to the same size as the loop around the shape intersection would have similar tradeoffs.

Topology like this is workable. It just requires some extra care when routing the loops around the surface and a willingness to trade some minor smoothing artifacts for increased speed and flexibility. This type of topology layout can be especially useful when there isn't enough starting geometry to match the segments in the intersecting shapes but completely redoing the base mesh isn't an option either.

Matching the intersecting segments.

Adjusting the number of segments in each shape, until everything lines up so the existing geometry can be used as the outer support loops, is a lot easier to do during the initial block out. This process can take a bit of trial and error but the increased control over the basic topology will help maintain the accuracy of the shapes and provide a clean set of edges that can be used to guide the loop flow.

Below is an example of what this process could look like. It may be necessary to visualize the final width of the fillet before committing to a specific segment spacing for both shapes. If modifier based boolean operations aren't available then an alternate option is to use another cylinder, with the same number of segments as the intersecting cylinder, that's the same size as the desired fillet.

After combining the shapes and adding the fillet around the shape intersection, any extraneous geometry can be removed using an edge dissolve operation. Use the loops that make up the fillet to constrain any shape changes between the large and small cylinders. This will help preserve the accuracy of the basic shapes and minimize smoothing errors caused by unintended deformation of the base mesh.

This strategy can take a bit more time to work through but tends to provide a cleaner topology layout with evenly spaced segments.

Complex shape intersections on compound curves do generate poles but with this topology layout they are generally going to be constrained to a very small area that's well supported. This extra support around the poles tends to reduce their potential to affect the mesh flow and reduces the visibility of any subtle smoothing artifacts.

The topology flow here isn't all that different from the previous example. It's just that the support loops around the shapes are a lot more consistent. There are certain situations where it does make sense to offset the intersecting shapes and average out any potential smoothing issues over a wider area. It's just that this particular combination of intersecting curves needs to be well supported to prevent unintended shape deformation.

Segment matching on the rest of the shapes is fairly straightforward and the flat areas can be used to either terminate the unnecessary support loops or resolve the mesh to all quads. Ideally the segment counts would be matched before adding any support loops but once the key surface features are defined it may not be strictly necessary to block out everything in one pass. The internal portion of the vessel can be generated using a solidify operation if desired.

Low / high poly topology overview.

Below is what the final topology layout would look like for both the low poly and high poly models. In this example the low poly model is derived from the high poly base mesh by using edge dissolve to remove the unnecessary support loops. Depending on the view distance, it may be necessary to add additional segments to the round over on the larger cylinder. This little bit of extra geometry would help provide a cleaner silhouette when viewed up close.

If a modifier based workflow was used to block out the shapes it would also be fairly easy to increase the number of segments in the individual shapes to optimize the low poly for close viewing. Without having to over-complicate the high poly or rebuild the low poly from scratch.

Recap:

• Try to solve most of the major topology flow issues during the block out.
• Match the segments of intersecting shapes and use existing geometry as support whenever possible.
• Examine the tradeoffs between different modeling and topology strategies and select the one that best fits the project's goals.

Also want to mention, for those who haven't already seen it, that polycount's dedicated modeling thread is a great resource for community feedback, topology layouts, and modeling strategies. It's something that a lot of artists have contributed over the years and there's numerous examples and discussions about the pros and cons of different approaches to the same problems. Even if the shapes aren't exactly the same, a lot of the basic fundamentals will still apply.

Subdivision sketches: miscellaneous cylinder topology.

These are a few examples of simple topology layouts that use segment matching to resolve shape intersections on curved surfaces. Only the key loop paths are shown, to simplify the presentation, and the n-gons could be resolved to all quad geometry using grid fill or manual loop cuts. Most of these shapes can be created with basic modeling operations. So this post is just a test for smaller pieces of content that don't require a lot of explanation. The next couple of posts will be the usual long form write-ups.

Angled cylindrical boss intersecting both flat and curved surfaces.

Toroidal section with intersecting cylinder.

Chamfered cylinder with rounded boss.

Subdivision modeling: mesh density Vs loop structure on curved surfaces.