Modelling approaches

Hi everybody

I’m still new at 3D modelling and was wondering if there is any rule to approach modelling objects

I mean, when is it best to use box and when to use contour/edge?

No. There are requirements from the end use and the pipeline, and options to approach modeling problems. There’s no best way to do anything, only options to choose from when all aspects are known. No one is handing out style points so the modeling style like box modeling or poly-by-poly modeling is not important.

What is important when learning modeling though, is not to obsess about modeling styles too much. To be effective with box modeling, it requires a lot of knowledge about structures (topology), about tools, breaking the structure down to steps for the tools to form a workflow, and about interpreting forms and proportions. It’s a fast modeling style, but it’s fast because all of that is handled at the same time. Modeling anything even slightly complex and trying to stick to just one modeling style is nonsense, and a bad idea when learning.

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The nice thing about Blender is it had made it practically possible to approach all of them. (Albeit the NURBS end of it could still use some work. Bsurfaces add-on gives yet another approach to that too.) So you can change what you’re doing on the fly to take advantage of an approach when you need to use it.

Box modeling: Main thing with it is blocking out and defining the volume of an object fast. And of course it’s easies to do that by extruding out faces.

Edge or vertex extrusion: Great for drawing out shapes in profile, so you can take a view and draw out segments to make something like a spiral.

Sculpting: It tries to parallel the real world process you’d have when working with clay. Best for intricate organic forms. Takes out the worry of edge flows in terms of putting something together, and has a high mesh density. Downside is that it can create a mess of tris. (Which is why retopo is a thing.)

NURBS: Uses curves or other math functions to define surfaces in a way that many CAD programs use.

Paths: Sort of like a simplified version of NURBs. Super handy for continuous extrusion forms like pipes or wires.

Retopo: Short for retopology. This is more like a process than a specific style. Generally you’re using one mesh as a template to produce a more organized one. Started out with sculpt based meshes because their tris don’t play well with Catmull-Clarke subdivision, and it helps because user defined quads also play better with deformation animations. Also turns out it’s useful for things like hard-surface where you want to re-define edge flows or develop a lower poly mesh while preserving the volume or surface shape of a higher poly mesh. Basically it gets interesting with the things you can do while free-form modeling over the surface of another thing, either with conforming to that shape in general or preserving alignments for things like seam gaps.

Boolean modeling: Uses previous shapes or primitives to define successive forms. Adding, subtraction, or unions.

Hard surface modeling: More of a style for things like machinery. Uses tricks like micro-bevels, and can focus on booleans in the workflow.

Organic modeling: More of a style for things like plants or animals. Curves and blended forms, various sweeping edge flows, etc.

Again all have their advantages or particular niche. It’s perhaps best to learn a bit of something from all of them, and then figure out what will be fastest for whatever it is you want to do. Essentially the more possibilities you understand, the more extended your own tool kit is to work with. And don’t forget that for things like nurbs or curves you can convert to the mesh (which is what it renders under the surface anyways) with Alt-C. And retopo in Blender is pretty easy with a few workflow tricks like using snapping and/or shrinkwrap modifier.

So in Blender it’s completely possible to box model a generic shape of a guy. Then put some tube like things in with paths. Then convert them to a mesh, and join them to the guy and weld up the vertices to be manifold. (Because sculpting doesn’t like non-manifold.) Then sculpt in a lot of crazy details to the guy with dyntopo. Then retopo the guy to a quad-based lower res mesh, where you can then normal and/or displacement bake the high poly sculpt. And when doing such you’ll find many approaches to get it done.