The object has a lot of repetitive surface features so try breaking it down into mirrorable or tileable segments. Working on a small portion of the mesh and copying it to create the rest of the shapes tends to be more efficient than trying to manually clean up a bunch of individual boolean operations.
There's a few different topology layout strategies and a lot of ways to approach modeling these shapes so what follows is just a general overview. What works best will often depend on the tool set and overall goals for the project.
When blocking out subdivision meshes it's generally considered best practice to match the number of edge segments on the intersecting shapes while also trying to use the existing geometry on the larger shape as support loops whenever possible. Subdivision modeling tends to generate approximate shapes so there's generally a trade off between shape accuracy [mesh density] and editability.
All things being equal: increasing the density of the base mesh tends to increase the accuracy of the shapes but it also tends to make editing the mesh more difficult. Try to balance these two elements by using the minimum amount of geometry required to accurately represent the shapes from the desired view distance.
The topology layout can be done directly on a curved mesh or it can be done on a flat mesh that's bent into the correct shape. Both approaches are viable but which makes the most sense will depend on the complexity of the shapes and the accuracy of the tools used to deform the shapes.
It's worth mentioning that, although mesh deformation tools can be a very efficient way to force less than optimal topology layouts into shape, inconsistent geometry spacing and untidy topology routing along complex curves can contribute to certain smoothing artifacts and make it difficult to add additional surface details later in the modeling process.
This is why it's generally considered best practice to maintain relatively consistent segment spacing along complex curves or at least space the segments in a way that's compatible with subdivision smoothing behavior. It's also helpful to be aware of how segment spacing can influence edge poles and how this may effect the smoothing behavior along the larger curved surface.
Here's an example of what this process could look like when modeling directly on a curved mesh. Start with a small cross section of the shape and adjust the number of segments in the curve until there's enough geometry to match the number of segments in the adjacent sides of the intersecting shapes. Split the cross section in half. Add an edge loop across the curve to match the remaining segments in the intersecting shape. Run the boolean operation and resolve all non-quad geometry (triangles and n-gons) to quads. Mirror the cross section.
Use a bevel operation on the highlighted edges to generate the support loops and confirm this section of the mesh subdivides cleanly before proceeding. Testing different topology layouts on small samples can help identify potential smoothing artifacts before investing a significant amount of time in adding all of the support loops to the rest of the object.
It can also be helpful to view the sample mesh from multiple angles with slightly different materials since this can help highlight any subtle smoothing artifacts that could cause problems with highly mirrored material values. Also consider the relative size of the object and the view distance of the player. Resolving minor smoothing issues on very small parts or objects that won't ever be viewed up close may not be the best use of time and may be good enough as is.
If the smoothing behavior on the sample is acceptable then continue mirroring, copying or instancing the tileable section of the mesh then extrude the final section and round over the corners. Support loops can be generated along the highlighted edges by a single bevel operation. Modifier based workflows can be used to automate a significant portion of the repetitive modeling operations. With this approach only a small portion of the object needs to be modeled and changes to this section of the base mesh will be pushed through the modifier stack.
Repeating this processes with additional geometry in the larger curve produces a different topology layout where the poles are closer to the shape transitions between the holes and the curved surface of the larger shape. This topology layout tends to produce better smoothing behavior along the curve by reducing the smoothing stress around the holes and the additional segments in the curve help increase the overall shape accuracy while also supporting the adjacent shape intersections.
The result is a slightly denser mesh with a much smoother surface and less noticeable smoothing artifacts when the curve is viewed from glancing angles. Some of the geometry between the holes, that runs perpendicular to the radius of the curved surface, can be dissolved to optimize the mesh but this will be covered a bit later.
Here's an example of what this process could look like when the holes are added to flat surface that's bent into a curve. Start by placing the geometry for the holes on a flat section of the larger shape's block out. Add support loops with relatively consistent spacing until the geometry in both shapes lines up. Extrude the flat plane and subtract or connect the holes to the top of the mesh. Bend the top section of the mesh to the appropriate curvature using a curve deform or shrink wrap operation.
Add support loops around the highlighted edges with a bevel operation and confirm the mesh subdivides cleanly. If everything looks good then continue and mirror, copy or instance the base section of the mesh to generate the rest of the tiled surface features.
While mirroring and copying sections of the mesh will help reduce the amount of repetative work required to create the shapes, it's also important to think through the order of operations to help maximize the efficiency of this modeling process. Try to work on the smallest section of the mesh (as is reasonably possible) and work through other repetitive features (like the rounded corners) before applying the lateral minoring.
With subdivision modeling there's almost always tradeoffs between shape accuracy and efficiency. Sometimes these tradeoffs aren't entirely obvious or can be slightly counterintuitive. At a given view distance there's almost always going to be a point where adding additional geometry doesn't really increase the visual quality of the model but it does significantly degrade the editability of the model.
How much geometry is actually needed to represent the shapes often comes down to how closely the object will be viewed and how well the topology layout subdivides. The smoothing behavior of this base mesh is arguably better than the other two examples and it can be further optimized by dissolving the highlighted edges.
Deciding where to split the tiling sections can also have a major impact on the topology layout and mesh density. This is where it's important to look at certain arbitrary restrictions, like assuming the mesh MUST be all quads, since that can exclude certain strategies that can eventually be resolved back to quads without a lot of work.
The example below shows how keeping the base mesh all quads require splitting the tileable segments along the edges between the holes and this ends up generating a lot more geometry than splitting the tileable segments through the middle of the holes and resolving the n-gons / triangles to quads after merging.
This is why it's important to evaluate the final
results and avoid over emphasizing certain technical elements. For game
art assets, if the mesh is easy to work with and subdivides cleanly then
more often then not it's passable.
When it comes to questions about modeling shapes there's a dedicated thread stickied at the top of the technical talk section so it's definitely worth skimming through that and posting future questions there since more people read it.
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