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Topology layouts for sharp, angled corners are fairly simple but often overlooked. This is why it's important to build a solid understanding of how different corner topology layouts impact edge flow, mesh complexity and smoothing behavior.

Most corner topology can generally be described as being either boxed or mitered. Boxed corner topology tends to produce a linear edge flow where adjacent support loops intersect and run off the end of the shape. Mitered corner topology tends to produce a continuous edge flow that follows the form of the underlying shape.

Both are viable but it's important to remember that efficient subdivision modelling is about cleanly directing edge flow while using the minimum amount of geometry required to accurately represent the shapes. The overall goal should be generate an accurate base mesh that's easy to edit and relies on the subdivision to generate smooth shape transitions and polished edges.

Here's an example that compares the underlying topology layouts and edge flow for both individual loops and support loops. The top row shows how boxed corner topology creates linear edge flow channels that direct the loops across the mesh until they intersect each other or run off into adjacent shapes. Compare this with the bottom row where the mitered corner topology creates continuous edge flow channels that direct the loops around the mesh without generating any extraneous geometry.

Enabling subdivision preview shows how the smoothing behavior deforms the underlying mesh and highlights where additional edge loops are needed to support the corners.

The linear flow of the boxed corner topology does provide some additional support for the outside corners but this extraneous geometry could be problematic if it runs out into other topology layouts on adjacent shapes. Mitered corner topology layouts tend to use less geometry and in most cases this will make it a bit easier to work with.

Another important thing to consider is whether or not the support loops need to flow around the shape to support additional details. The continuous edge flow of mitered corner topology tends to make it easier to select and adjust the loops that support the shapes.

Mitered corner topology also tends to make it easier to make consistent adjustments to adjacent corners without effecting adjacent surfaces. With that said, there are certain edge cases where the linear flow of boxed corner topology is needed to support additional shape intersections and surface features.

Which topology layout makes the most sense will depend entirely on how the support loops interact with the surrounding shapes and whether or not the mesh needs to be edited again in the future.

Choosing to use mitered corner topology isn't always that obvious. Certain types of shape intersections do require grid topology or intersecting loops to support the shapes but they can often be further optimized by using mitered corners on the perimeter support loops. The first and second row in the example below shows how support loop topology can be optimized to produce better results with less geometry.

There's also some specific edge cases, similar to what's shown in the third row, where secondary surface features require additional support and support loops need to turn corners or flow around complex shape intersections. In cases like this the mitered corner topology will help direct the edge flow without creating extraneous edge loops that flow off into adjacent shapes.

Optimizing the topology layout and edge flow will help reduce extraneous edge loops that tend to increase mesh complexity without providing significant improvements to the overall visual quality of the final mesh.

Effective subdivision modeling is about balancing accuracy and efficiency so it's worth taking the time to block out all of the major shapes and figure out the most effective topology routing before jumping in and investing a significant amount of time adding support loops.

Last weekend's hard surface sketch continues with the camera rig theme. Here's a subdivision model of my favorite lightweight camera mount for standard 15mm rods.

Another modifier heavy workflow where the basic shape is created with a series of boolean operations on a mirrored base mesh. Most of the support loops are generated by modifiers that are controlled by vertex groupings and edge weights. The waffle pattern on the rubber pads is a floater that's generated by a simple tile pattern and trimmed with a boolean operation.

Some parts were reused from the previous project and everything is built to scale in real world units.

Bottom row: base meshes with the mirror and bevel / chamfer modifiers turned off.

When it comes to modifiers and non-destructive modeling there's a lot of different ways to approach creating the shapes but it's always important to evaluate the overall practical efficiency of the entire process.

Some artists recommend only using unedited primitives with boolean operations. The argument in support of this strategy is that everything can be walked back to the original starting primitive and avoiding mesh edits will maximize the non-destructive editability of the surface features. While this type of modeling strategy can make sense on projects where large, continuous changes can be expected, there's often a significant efficiency penalty to brute forcing shapes with unedited primitives and over complicating the boolean stack.

The idea that everything needs to roll back to unedited primitives to mimic CAD processes doesn't really hold water because drawing flat dimensional sketches and extruding basics shapes is an actual process used in CAD workflows.

In most cases it will be more efficient to combine modeling operations wherever possible by editing the underlying shapes that drive the boolean operations. Keeping these mesh shapes simple and controlling surface features with other modifiers reduces complexity without sacrificing editability.

Here's the basic modeling process for the camera mount's metal base plate. Start with the overall dimensions and use snap to grid to keep all of the mesh components in line when blocking out the basic shapes. Use bevel / chamfer modifiers to add chamfered and rounded corners that can be adjusted at any time. Both edited and unedited primitives can be used to define key surface features. Sketch out flat outlines of the complex pocket features and use modifiers to solidify the shape and add corner radii.

Most boolean operations will leave behind some unnecessary geometry. Once all of the major features are present and the model is approved then it should be safe to apply the boolean operations and cleanup the mesh by triangulating and running limited dissolve.

This editable base mesh can then be used to create both the high poly and low poly models. Add a bevel / chamfer modifiers to preview the edge width before cutting in surface features that are close to the outside of the shapes. A mirror modifier is used to simplify the base mesh and bevel / chamfer modifiers, controlled by face angles, edge weights and vertex groups, are used to automatically generate support loops that can be adjusted at any time.

Here's the modeling process for the rubber pads on the top of the base plate. Start with the basic shapes and use bevel / chamfer modifiers to generate the corner radii and support loops.

The waffle pattern is a simple inset tile that's repeated across the top of the surface and trimmed with a boolean operation. This surface detail is floating geometry [floater] so it's basically a one sided mesh that sits above the base mesh. More often then not it will be more efficient to add minor surface details like this using texturing tools.

There's a lot of basic shapes and a few complex intersections with compound curves but the base mesh is fairly simple. All of the support loops are generated by un-applied bevel / chamfer modifiers and remain fully editable.

The simplicity of the base mesh and use of modifiers means that making minor changes to the shape won't be an issue. Any major changes can be made by going back to the block out model with the active boolean operations.

Additional standardized parts can be pulled from previous projects to save time. Here the flag head clamp screws are reused from the rosette clamp model.

Keep the base mesh simple and use modifiers whenever possible to avoid repeating manual editing operations. Avoid over complicating non-destructive workflows and use destructive editing where it makes sense. Work in real world units and reuse components from other projects.

Removing subdivision smoothing errors from shape intersections on curved surfaces is a common theme for questions about hard surface subdivision modeling. A lot of these questions are about pinching and stretching issues near corners and around shape transitions. Most of these questions have been asked countless times and more often then not have been answered with some variation of "Just use more geometry." but is this really the best answer?

More importantly, if using more geometry is the best answer to these questions then how much more geometry is enough geometry?

In most cases: increasing the geometry density does tend to increase the overall accuracy of the underlying shapes but it also tends to increase the complexity of the base mesh. Adding unnecessary complexity will make it harder to edit the base mesh and using too much geometry on a small segment of the model can generate it's own type of smoothing artifacts.

Outside of the obvious cases where there isn't enough starting geometry to support the intersecting shapes, arbitrarily increasing the number of segments in the starting geometry can be a viable solution to remove some smoothing issues but there's diminishing returns on the trade off between accuracy and efficiency.

In some cases there's already more than enough starting geometry and the smoothing issues are caused by improper geometry distribution or topology flow that disrupts the natural forms of the underlying shapes. Fundamentally these type of smoothing issues are problems with the underlying shapes not the geometry density. Blindly increasing the amount of the geometry will work but it's a brute force approach that doesn't address the root cause of the issue.

Subdivision modeling is a [mostly] approximate process but the smoothing behavior is relatively consistent across all platforms. To understand how subdivision smoothing works it's important to break things down into their simplest forms and observe the fundamental smoothing behavior of the basic shapes. Once subdivision smoothing behavior is understood it becomes easier to plan out efficient topology routing solutions for complex shape intersections.

Below is an example of basic cylinder geometry:

Row 1: The edges that define the cylinder wall segments tend to pull inwards uniformly. To counter this it's necessary to add support loops around the edge loop at the top and bottom of the cylinder. These support loops counter the uniform inward pull and deform the top of the shape into a flat plane with a rounded transition into the cylinder wall.

Row 2: Moving an individual segment of the cylinder wall (in or out, up or down, right or left) will change the spacing between the segments and this causes the wall of the cylinder to deform. Failure to maintain concentricity and spacing of cylinder wall segments is a major cause of smoothing artifacts on curved surfaces.

Row 3: Adding edge loops that run perpendicular to the cylinder wall segments has virtually no effect on the curvature of the cylinder wall. Placing additional edge segments between existing cylinder wall segments tends to disrupt the subdivision smoothing which flattens the cylinder wall. Adding support loops to either side of existing cylinder wall segments tends to disrupt the subdivision smoothing and causes pinching.

As shown in this example: moving existing cylinder wall segments can cause undesirable deformation. Additional geometry that runs perpendicular to simple curves tends to have a relatively minor impact on smoothing behavior along the curve. Additional geometry that runs parallel to existing edge segments in the cylinder wall tends to disrupt the smoothing behavior and is a major cause of smoothing artifacts on curved surfaces.

To avoid these kind of smoothing errors it's important to maintain a relatively consistent spacing between curve segments and ensure that the smoothed mesh components and surface features are concentric to the wall of primary shape.

Below is an example of basic rectangle geometry:

Row 1: The edges that define the volume of the rectangle tend to pull inwards uniformly. To counter this it's necessary to add support loops around the edges that define each face of the rectangle. These support loops counter the uniform inward pull of the smoothing and deform the basic shape into a series of flat surfaces with a slightly rounded transition between each surface.

Row 2: Adding geometry to or moving geometry along flat surfaces [between the outer support loops] generally has no major impact on the overall shape. Moving surface geometry components out of plane does cause deformation.

When properly supported, flat surfaces are generally very tolerant to substantial topology changes so they can be a good place to simplify the mesh by culling unnecessary edge loop propagation. Flat surfaces that are angled, relative to other surfaces, should be flat to themselves. Keeping shape boundaries well supported and individual surface coplanar should be all that's required to prevent major smoothing issues on shapes with flat surfaces.

The previous observations seem fairly obvious but it's important to keep this information in mind when merging shapes. Trying to add geometry to curved surfaces, without accounting for the effects of edge loop propagation, often results in pinching and stretching errors.

The modeling process shown below seems to work but once the final support loops are added to the cube they run off the cube and parallel the existing geometry of the cylinder. This changes the segment spacing in that area and causes undesired cylinder wall deformation.

Moving the extra edge loop along the cylinder wall can reduce the severity of the smoothing artifacts but it generally doesn't fully resolve the issue. It is possible to manually re-adjust the segments so things are relatively smooth but this often requires a significant time investment and tends to introduce other issues with the overall accuracy of the major shapes.

When asking for feedback on resolving this type of smoothing error, it's very common to get a vague answer like "Just add more geometry." and that's understandable, because this strategy is simple, easy to explain and generally works. Sadly this advice is often simplified into something along the lines of "Just double or triple the segment count." Most of the time this will work but it's not an optimal strategy and this kind of advice ignores the wider context of what's appropriate for a particular part of a model.

Arbitrarily increasing the complexity of the model without addressing the root problem that's causing the smoothing error is a sure fire way to reduce process efficiency. It will also make it more difficult for anyone who has to come back and make adjustments to that part of the model. This is why it's important to evaluate what's actually causing the smoothing error and take other factors (such as object size, average view distance, complexity of adjacent mesh segments, etc) and make an informed decision about where to add the additional geometry.

A better answer is: match the segments of the intersecting shapes and use the appropriate amount of geometry to match the necessary edge loops on the adjacent shapes.

Below is an example of how the number of segments on the larger cylinder can be increased to match the number of edges that make up the intersecting rectangle. As discussed previously, the number and position of the segments in the cylinder wall are critical elements that influence smoothing behavior. It's also generally considered best practice to use the existing geometry as support for the shape transition area around the shape intersection.

The process of segment matching is fairly straightforward and this is one of the reasons why it's important to block out all of the major shapes before investing a significant amount of time in adding support loops and other details. Establishing accurate shapes with good topology flow between them will make it easier to place and route support loops that won't cause major smoothing issues.

With subdivision modeling: the goal should generally be to use the minimum amount of geometry required to effectively hold the required level of shape accuracy and surface details.

Once all of this is understood and put into practice it becomes much easier to generate meshes that have a better balance between shape accuracy and process efficiency. Here's an example of the previous modeling process but the number of segments in the cylinder is increased slightly to match the number of segments required to support the intersecting cube.

It's also important to view the mesh from multiple angles and evaluate the total prominence of any smoothing artifacts. A shiny preview material with a wide highlight roll off can really light up surface imperfections when a mesh is viewed from off axis glancing angles. Using this type of material and toggling the subdivision preview will help make it easier to identify the severity and source of any smoothing errors.

When increasing the mesh density there's a definite fall off in quality as the amount of geometry increases and there's a corresponding jump in editing difficulties. This is why it's important to consider how visible a smoothing error is before investing a significant amount of time trying to remove it. If there's minor smoothing errors in a small segment of the mesh that's not regularly visible to players or if minor smoothing errors are covered by high frequency surface normal details then there's minimal benefit to achieving perfection in these areas.

Below are three examples [with increasing mesh density] to compare how increasing the amount of geometry effects the overall visual quality of the subdivided mesh and editability of the base mesh.

Here's the cube intersecting a 12 segment cylinder.

Here's the cube intersecting a 24 segment cylinder.

Here's the cube intersecting a 32 segment cylinder.

As the density of the mesh increases there's a clear fall off in the rate of change at which the difference in visual quality is perceivable.

This means that, past a certain point [for an object of a given size, viewed from an average view distance] increasing the number of segments in a cylinder will no longer have a measurable difference to what players experience. At this point there's very few reasons to continue adding additional segments.

Where good enough is good enough will be different from project to project but there's a distinct case to made against over complicating the mesh. Time spent perfecting something that doesn't directly effect the playability or player's perception of the overall visual quality of the model is time that could be better used else where. This all circles back to why block outs are so important.

Another point worth making is that there will be situations where it's either impractical, impossible or imprudent to increase the number of segments in the base geometry. Often there's cases where parts are very small or constrained by adjacent geometry and the cost of making minor improvements far outweighs leaving in minor smoothing artifacts.

In situations like this it's best to try and reduce the visibility of minor smoothing artifacts by manually adjusting the mesh to help pull everything to shape when subdivision is applied. Often small, soft smoothing artifacts can be covered by surface noise in the normal textures.

It's generally acceptable to make minor manual adjustments to small details constrained by adjacent topology but keep in mind that using this to make large changes to most of the shapes in an object can produce undesirable results. Excessive manipulation of geometry components to compensate for an issue caused by a lack of adjacent supporting geometry can generate it's own type of smoothing issues and tends to decrease the overall accuracy of the shapes.

Below is an example of what this process can look like. Dissolve unnecessary edge loops and with subdivision preview enabled, scale or move the offending geometry components back into line until the stretching or pinching issues are minimized.

The results are far from perfect but it is an improvement on the original base mesh's smoothing behavior. This strategy is really only useful on making minor improvements to parts that would have otherwise required reworking a large section of the mesh to blend in. Again, it's important to evaluate the root cause of the smoothing issues and address that whenever possible. This solution is only passable on minor parts that are generally out of the player's close view.

All of these principles can be applied to other shapes. Below is an example of how this works with cylinder to cylinder intersections. Start by blocking out the major forms then match the number of segments in the intersecting shapes. Preserving the natural shape of the underlying geometry will reduce the likelihood of prominent smoothing artifacts.

The mesh in this example is passable if the geometry density is constrained by adjacent shapes but it does have some deformation issues caused by the limited amount of geometry in the larger cylinder.

Here's another example that shows the same modeling process with more starting geometry.

The overall goal should be to preserve the natural forms of the underlying shapes and increasing the geometry density to closely match the segments of the intersecting geometry tends to improve both shape accuracy and smoothing behavior. Using the appropriate amount of geometry will help provide a good balance between shape accuracy and process efficiency.

it's also worth noting that transitions areas around shape intersections can provide natural support loops that should be used to constrain any smoothing errors caused by any differences between the geometry of the intersecting shapes.

Below are three examples to compare the difference made by increasing the geometry density of intersecting curve shapes.

Here's the small cylinder intersecting a 12 segment cylinder.

Here's the small cylinder intersecting a 24 segment cylinder.

Here's the small cylinder intersecting a 32 segment cylinder.

After a certain point it becomes necessary to also increase the number of segments in the smaller cylinder to match the segment increase in the larger cylinder. Failure to match the number of segments on curved intersections will generally just move the smoothing issues from one shape to the other.

Intersecting shapes with flat segments and sharp corners tend to be more demanding than circular shapes with soft corners. This circles back to the idea that it's possible to adjust the underlying geometry to compensate for minor smoothing issues. With cylinder to cylinder intersections it's often possible to average out any minor smoothing issues over a wider area without needing to increase the density of the starting mesh.

As shown in the example below: there is a minor decrease in overall shape accuracy but the tension in both curves helps pull everything back into shape. The accuracy penalty for making minor shape adjustments on this type of geometry tends to be much less than when it's used on intersecting shapes with strong linear features.

Becoming proficient at subdivision modeling does require practice but it also requires learning to see the underlying shapes and being able to extrapolate new solutions from existing knowledge. Limited experience can be a barrier that makes it difficult to take relevant examples and apply them to new problems. The basic principles will work on most shapes. Start by learning the fundamentals and build up from there.

Below are a couple examples that show how the topology for a through hole is essentially the same as the topology for a boss. The only difference is one pushes inwards and the other pokes outwards. There's very little magic. It's mostly about repetition and rhyme.

There will be challenges along the way but it's important to keep going and to study how other artists have resolved similar problems. Sometimes it seems like it can't be that easy [because sometimes it's not] but it just take thoughtful practice and evaluation. Experimenting with different topology solutions and comparing the results can help identify winning modeling strategies.

Here's another example: surely an oblong through hole must have different topology than what's needed for a circular through hole! Nope. It's pretty much the same, just split the circular through hole and fill the gap. Fundamentally it's mostly the same or variations on a theme because the underlying process (subdivision smoothing) is relatively consistent. It's all repeatable which is why it's important to research, experiment, evaluate and repeat.

Below is another example that's a variation on the theme: does it need more geometry or does it just need better geometry?

Well for starters it's overly complicated and poorly organized. But remember that there's cases where more geometry is a brute force solution to problems with the underlying shapes. Effective subdivision modeling is about using the minimum amount of geometry required to accurately hold the shapes.

Here's an example of how a better result can be achieved with the same amount of starting geometry. Start by defining ALL of the basic shapes, use the existing geometry as support for shape intersections and place the intersecting geometry on or between existing segments as appropriate.

Below is a comparison of the same shape with different mesh densities. Under optimal conditions there's very little practical difference between all of these. With that said, there will be certain situations where increasing the sharpness of the edge width by adding additional support loops will require more geometry to support the increased edge sharpness.

Again it all comes down to what the project requires and knowing how and when to make tradeoffs between accuracy and efficiency. This is why it's important to block out everything beforehand and evaluate how accurate things need to be based on player view distance.

How about this shape? More geometry or better geometry?

Parallel edge propagation is making an absolute mesh of the underlying shapes. This is a case where increasing the geometry density will help and so will adjusting the placement of the cylinder's edge segments so the intersecting geometry is properly supported by the existing geometry.

Here's one example of how these smoothing issues could be resolved without throwing a lot of geometry at the problem. Start by blocking out the shapes then match up the segments of the intersecting shapes. Try to preserve as much of the existing geometry as possible and use it as support for the shape intersections.

The initial result is much cleaner than the previous version but it does have some unwanted deformation near the peak of the circle at the end of the slot. This minor imperfection can be resolved by shirking the height of the circle's center vertex at the surface of the curve.

As before, increasing the geometry density does tend to increase the overall accuracy of the shapes. The question is how much has this increase improved the results and how much has it complicated the underlying mesh? The answer depends on the quality goals for the project.

It's also worth noting that, when increasing the geometry, it doesn't always have to be an even number and the segments don't always have to align perfectly. it's very common for artists to stick with common even numbers like 8, 16, 32, 64 or 12, 24, 48, etc. All of these numbers are easy to work with and visualize but sometimes it's better to use less conventional numbers like 10, 14, 20, etc. Sometimes it's more important to line things up with the intersecting geometry than it is to have a common number of segments.

@Nominous Thank you, glad you enjoyed the content. Overall I'd have to agree that getting a clean and consistent result is (almost always) an important priority.

Modifier based modeling strategies can be a really efficient way to work since the underlying mesh is kept relatively simple. This makes the model easier to edit since most of the support loops are generated by the modifier system and will remain editable (via modifier settings) throughout most of the modeling process.

Offloading repetitive modeling tasks to tools and modifiers should reduce manual editing and increase shape consistency. The structure of the underlying mesh topology tends to have the single greatest influence over the quality of the geometry generated by modifiers and other tools. If the input mesh is clean, straight and well organized then the support loops added by the modifiers should be clean, straight and well organized.

It should be possible to re-create the previous example without having to apply any modifiers. Here's an example that shows the base mesh and modifier settings required to get this to work in Blender 2.91. Depending on the shapes, angle based modifier controls aren't always accurate or reliable so sometimes it's necessary to use grouping or weights to achieve the desired results.

Correct: there's a significant efficiency bonus to using the same base mesh for both the high poly and low poly models.

Using modifiers to control the geometry density of specific features means this process works in both directions since the parameters can be used to add or remove geometry from across the entire mesh or specific areas.

How complex this setup is depends entirely on the project and the complexity of each individual part. It's all about balancing shape accuracy and editability to efficiently arrive at a result that hits the project's quality goals.

This process is something I plan on covering in the near future.