So im watching the BlenderBros free course Hard Surface Modeling Jumpstart
and in there they are modelling in fully orthographic. i have always used perspective other than the fully side/top views. and i even heard perspective view is “realistic”
so why are they doing the course in orthographic?
It’s really just a matter of preference. There may be some rare situations where you’re eyeballing something, and you don’t want the sense of depth inherent with the perspective view to throw off your guesstimations, but for the most part, it’s all down to taste.
Personally I prefer UV unwrapping in orthographic, I don’t need perspective or depth for that. I also like modeling some stuff in orthographic- character clothing, for example, really doesn’t need depth and instead you need to see as much as possible at once. Ultimately, yeah, it’s just preference 
Ortho provides technical accuracy. Perspective gives a sense of depth … which can get tricky.
Ryuu is an awesome instructor! As a beginner, I too have signed up for their course!
That’s a great point!
makes sense … once upon a time, when i was in a drafting class, everything was done in ortho. but that was all on paper, where it would have been even trickier to do perspectives on machine parts or whatever random thing they gave us to draw.
I still have all my drafting equipment, ha!
By principle there are thousands of focal lengths for perspective views - but only one orthographic view. It is great to see sizes of all objects all at once, one can compare anything to anything in whichever viewport camera position. Thus I think ortho is kind of special.
i dont understand
measurements et al are consistent
take for example this image found with a quick google search:
(apparently comes from video: https://www.youtube.com/watch?v=dUJzpz8J9xw )
in the orthographic, you can tell that the the upper/lower faces are parallel to each other, that the upper edge is the same length as the lower edge, in fact all opposing edges on any visible face are equal in length, forming a parallelogram, which understanding that this is orthographic, informs you that the sides are squares, that all three (visibable) z-axis edges are equal in length, etc etc
in the perspective, while looking more “natural” to our eyes, none of these are guarantees, hence the numerous optical illusions we see posted on social media. the three z-axis edges are two different lengths, the upper and lower faces may or may not be parallel, the top edge/bottom edges are not the same length. while it .appears. to be a cube, it may be quite slanted, because you’re missing some key information that you make assumptions for. for example, what is the focal length of the “camera” that took this shot, was it lensshifted, etc etc.
To add to this- measurements are always consistent in orthographic view. Trying to follow, say, an ultra precise blueprint in perspective views is simply not possible
I’m wary of “always” and “never”, but generally, yes
Yes, most general speaking. Perspective can easily be subdivided into equal parts, think of telephone poles going along a straight road, or the railroad ties beneath railway tracks.
Perspective needs vanishing points on a horizon line of some sort to which parallel lines converge. And that can be tuff to accurately measure. Even with a grid, ha! Especially when it goes beyond the cone of vision!
For most part Orthographic is without distortion. Parallel do not recede/converge to a vp.
But with Ortho you can also show depth, but this is done with line weight and such.
Hope that helps.
When doing organic modeling, and especially faces, it’s great to check the result in perspective.
It’s also good to take into consideration what focal your references are using.
This page got a lot of examples showing how focal lengths going to nearly ortho to nearly fisheye change a lot :
So for instance, if your references are using a 50mm but you’re modeling in ortho the model is going to get some extra distortion, and therefore might feels weird when seen under a 50mm lens,
Obviously, we can’t always tell precisely what kind of lenses has been used on a photo, or even more if the reference is a cartoony hand drawn model.
But at least it’s good to asks ourselves these questions and at least look at the model through the final lens.
For hard surface modeling, I tend to prefer working in ortho, and even on characters I prefer to model in ortho, but this can lead to surprises as said earlier.
Hope that helps,
Have fun !
like @joseph says, i’m also wary of “always”/“never”.
for me it depends on the end goal. if i were designing a part to be machine printed (especially if someone else is doing the printing/machining) yes, i’d use ortho. but since most of my blendering is more … abstract art? lol i go with perspective, more how the eye would view it, even if it’s something others i often see do in ortho. that said, neither of these are carved in stone, and i may sometimes veer from either. again, depends on the end result i am after.
now before rendering, if i’m say, modelling a car (something i haven’t done in a zillion years), i tend to model in a 3 axis layout (straight on X Y and Z axis)… ideally laid out like one would do in drafting. for the 4th pane, that i flip between ortho / perspective, depending on what i’m needing to see at the moment. that was when i was using Lightwave for modelling, in the ancient times. 
since i’m still getting used to all the info Blender presents, i’m now usually in one view (with other type info in the other panes), i’m just in one pane here, but constantly using the view widget to change between axis.
i really should figure out a way to have my graphics tablet out here where i can use it as an extended display.
