Automotive grille parametric modelling-Alias/Grasshopper

[TomTom (Tom)]

somehow like this section.

Did it help?

[davidcockey]

@TomTom

There are some exceptions but in general it is always Bezier. If a toolmaker makes a Nurbs out of is possible, but these people are not supposed to modify the shape itself.

I assume “Bezier” means single span and “NURBS” means multiple spans. Any Bezier curve has an exact equivalent single span NURBS curve.

@Proterio

I guess I am trying to get some information that I can use to actually produce a Grill. For example, what kind of plastic is specified, what is the thickness of the webbing material at the thinnest point, how deep are the webs to give it enough strength IN GENERAL. I understand these are all dependent upon the design, in this case irregular polygons, but thumbnail numbers would be helpful to get my design closer to the real world )

Aftermarket part or OEM part?

Choice of material for OEM parts depends on multiple factors including performance requirements, appearance requirements, volume (number of parts to be built), ability to match other surfaces if required, manufacturing capabilities and cost. Frequently tradeoffs are needed to reconcile conflicting requirements.

[TomTom (Tom)]

@davidcockey

I assume “Bezier” means single span and “NURBS” means multiple spans. Any Bezier curve has an exact equivalent single span NURBS curve.

I know this, and you know that I know this. At least if we speak about a mathematical level. On a computational level this is not true. Some applications differentiate between these, since a pure non-rational Bezier geometry doesn’t contain any information of Weights, Knots and conditional branches to deal with multispan data. Thus they are “lighter” on a computational level. Algorithms can be much simpler when excluding certain properties.

Ideally a clean multispan skin might result in a clean and equally surfaced skin. But this is the ideal world. In practice people using multispan data, creating heavier geometry. Some exceptions are e.g. spheres and circles. But any rational geometry is much harder to further work with… Try _flowAlongSrf on a rational and a non-rational surface for example and see how this affects the cp count of the morphed geometry.

As I said, I don’t want to start a discussion about it. As I said not all reasons and concerns are valid points if you ask me. But if we speak about (german) oem parts, the computational representation is Beziers (or single span Nurbs as a subset). At least for all the models I have worked at/with.

[TomTom (Tom)]

I believe the reason why certain single-span-only tools are still not part of Rhino, is the fact that any command needs to satisfy the multispan solution. For some functionality this becomes really difficult. Think about surface extrapolation or surface splitting (untrimmed). These are so important for daily modelling, doing similar things in Rhino is always a difficulty to workaround. Implementing these for multispan is much more demanding and so we see no true equivalent yet.