Quote: "I use Blender for all my occasional custom modelling needs. It's a lot easier these days to get into from scratch; although it will take some time before you can make anything half decent. Practise makes perfect. Start off with a cube. Work out how to texture it. Extrude some stuff; add some extra geometry and texture that. Watch some tuts."
I made plenty of mistakes when I started out modeling that did more harm then good, there is quite a bit more styles then shape modeling.Block out modeling works well in-conjunction with shape modeling and then there are other techniques like drawing and converting to mesh, things like rotoscoping is useful as well.
Overall you need to pick a style(s) or combination of it that works best, as you will at one point or another make use of all techniques all at once or a few at a time you need to practice the basics like beveling, boolean operations, polygon extraction, merging of faces, edges and points. The there are things like polygon deformations, duplicating polygons via a curve or an axiz.
You need to learn what each function does and how it may be applicable to your model, as you won't be able to create decent shapes without these additional operations at you disposal. Tutorials takes you step by step about how create a coffee mug, but none really explain why it is being done this way or what other uses these functions have that they use when creating their tutorial models.
Learning what these additional functions do beforehand is quite useful going into tutorials as it makes following them much easier and you can do a lot of shortcuts as a result of learning some of the functions that is intended to make life easier as well as making more natural shapes.
Take this image for example if you want to model this.Which is a relatively straight forward modeling experience, it uses several functions previously mentioned, and you will be making use of them.Once you decided what you want to model get as many reference pictures as you can of the item you are planning to model top/left/right/side, quite often you can't get bottom view as well it is quite rare. So often you can search for the specific part, if you know the name in this case I would like to see the bottom view of the engine block.Often you may need to find a completely different brand or image that gives you some idea of what it looks like. If you don't know often you just free hand it and guess what looks good, the last part comes naturally eventually.
Second part is studying the shape(s) contained within the model mostly squares and cylinders. This is where block out modeling comes in extremely handy tool, it helps visualizing the different shapes needed in the construction of the model. In the case of this model there is quite a bit of guess work as not every thing is visible even with all angles available. Like the fuel tank on top. The output panel on the side little odds and ends that you will need to model by your own design, even forgo completely.
Dvader mentioned low polygon model, well not entire true, you don't have to start out with low polygon. You actually want to model reasonably high polygon, with lots of detail, used for creating normal maps and bake details into a low polygon model. Considering you won't have actual textures for this model and will have to make use of tools to paint textures like substance painter, or quixel. Generally I use a different approach where by I paint normal details into the model. While I may use a high polygon model, I make use of polygon reduction afterwards, it is a function that reduces the amount of polygons on a model or part of the model. In this case the cylindrical frame that the engine sits in. It requires several functions to create.You will have to create a cylinder primitive and use a function like extrude via curve. The curve is some thing that you have draw in the shape of frame holding the engine.Benefit of using a function like this is that the polygons is attached to the curve so that you can manual edit and move points around the curve to better shape the frame as you need it to be. After freezing the function, when you are happy with the shape you can use polygon reduction that will get rid of unneeded edges on the shape you just created while still retaining the original shape or close to it.So you don't necessarily start out with a low polygon model and generally better to use more polygons at the start which can be reduced later on. You do want to get as close to the shape of the thing you want to model, if in doubt use more you can always reduce afterwards.
I probably over complicated things with this explanation, but the idea is to train your mind to look at what you want to model and mentally get an image of what shapes it contains and how you will use the tools within the software to create said shape. Once you actually start seeing the shapes contained with in the object you want to create it take a few seconds and you can easily blockout the general shape of the model from the shapes seen in image or object you want to model.
Essentially if you are going to learn to model you will need to learn the tool you will be using and the most important functions found in the tool you will be using most often. There is some functions in my tool I will never use, so if you can learn the important ones it will make life much easier when modeling as well following, tutorials. I never watched tutorials as it never really helped other then making me even more confused as i most often didn't understand what they were doing and often just gave up.
So I had a messy experience and delayed any progress I could have made with a solid foundation and understanding of what I was modeling.Best advise I could give is learn the software and learn what functions it has, before attempting to model any thing whether a simple barrel or box, do the basics over and over and over. See what the beveling does or extruding of edges, points and faces.
It is basically like learning how to draw but in 3D and drawing on paper it also uses primitive shapes, circles, squares and triangles as a starting point when learning, but as you become more accustom to the shape you drawing you become slightly less reliant on them but still helps if you needs to get right perspective and scale.
Once you have done it many times, it becomes second nature and fun, just practice on the modeling part, texturing and uvmapping is a skill and art form on its own and will take many more weeks to understand and practice on it's own.It is daunting task, and tutorials expect you have some prior knowledge, so watching a tutorial on creating a character isn't going to help it requires that you know the basics and have a foundation, so don't bother with them, start out with tutorials teaching you about the software and the functions it has and how to use them, once you have done that every else will fall into place.
Here is and example of a model I made using the blockout method, this is also the first ever vehicle I decided on making, it's not perfect, but looks decent enough.
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