Confused about Field of View Camera Settings


#1

I am very new to SketchUp and I am a little confused about the Camera settings. I would like to know the proper settings in SketchUps Camara - Field of Views. I read the users guide and it gave the settings for a 45.deg or 35mm which is equal to 35mm Camera.

If I were to draw a standard 2-point perspective drawing by from 2 or 3 elevation drawings (example: front, top and right sides) of an object. What would be the proper settings in SketchUp in Degrees or MM that would give me the same undistorted visual / hand drawn results? If I have not made my self clear have made a link to a an example of how 2-point perspective is normally done by hand.

http://www.automotiveillustrations.com/tutorials/drawing-2-point-perspective.html

If some can help me out I would appreciate it greatly.


#2

Who said 2-point was undistorted? Since this method ignores the z-axis vanishing point to reduce manual labor on hand-drawn perspective drawings, it is something of an anachronism in SU. 2-point perspective is actually more distorted than the standard full perspective view generated by SU. SU offers a 2-point view on the Camera menu, but it is a fixed view that reverts to full perspective as soon as you try to orbit.

The default Field of View is 35-degrees, I believe. That is pretty good for outdoor scenes; for indoors you may need a wider Field of View so you don’t end up staring at one small spot on the wall–maybe 50- or 60-degrees. In general, the lower the number the more the view resembles parallel projection; at 0 the two are essentially indistinguishable. At very high values, say 100-degrees or about, the view starts to resemble a fish-eye effect.

-Gully


#3

Select Camera >> Field of View and immediately type the number 45 followed by a return (the degrees should show in the bottom window). Then pan/zoom/orbit to the view you want and select Camera >> Two-Point Perspective. You will see “Two Point Perspective” in the corner of the screen. You can now pan and zoom to get the exact framing you want. As soon as you orbit, however, you will lose the two-point perspective view.


#4

So I gather Gully when the “Perspective” feature is checked in the Camera Menu this is a 3-Point perspective view and is the SU default? The 35.00 Deg setting would this be equal to what the human eye would see normally, or would this be different setting again? I find the 35 mm Camera setting a little to distorted even for 50 mm lens.

Dale


#5

Yeah. Parallel projection is probably best reserved for aligning things and producing customary paper documentation. I’m not sure what the 2-point option is best for–nostalgia?

I seem to remember that the default Field of View is different for Make and Pro. Maybe 40 degrees for the former and 35 for the latter.

Even though I’m pretty sure I’m human, I’m probably not qualified to speak on normal human vision, since there’s always been something or other wrong with my vision, and I suspect your book knowledge about human vision surpasses my own.

I encourage you to play around with the FOV control and get a feel for the numbers and the look they produce. You can use the Zoom tool shortcut (Z) and then type the applicable FOV number, which will appear in the Measurements box as you type. Do not click the Measurements box to give it focus. Just type Z and then enter a number in degrees for FOV.

-Gully


#6

Thank you for you information and you time :smile:

Dale


#7

If I were taking a class in perspective drawing, I might be tempted to layout the 3D geometry in SketchUp and then use the two-point perspective to help me fulfill a class assignment. I think it’s also useful for technical drawings like cabinetry, etc. Here’s an example from Wikipedia:

The question about the Field of View (FOV) is interesting. According to the docs:

“Adjust the screen to an exact perspective or camera lens by typing an exact value in the Measurements Toolbar while the Zoom tool is active. For example, 45 deg sets a 45 degree field of view and 35 mm sets the equivalent focal length of a 35mm camera. Press and hold the Shift key while in the Zoom tool to visually adjust the camera lens or field of view. Remember, changing the FOV keeps the camera in the same location in 3D space.”

and

“the default is 35 degrees in SketchUp and 30 degrees in SketchUp Pro”.

While the FOV of the human eye is nearly 180 degrees, the FOV as it relates to cameras and SketchUp is a matter of the relative window size and object distance that is under consideration:


#8

Just a note about the field of view in SketchUp: The FOV numbers do not match the ones given to a 35 mm camera lens. In SketchUp the FOV is measured vertically across the model window, while the shape of the window varies, whereas in a camera the measurement applies to a diagonal of the picture frame that has fixed 2:3 proportions. A SketchUp view with a FOV of 50mm is considerably more wide-angled than in a camera with a 50 mm focal length lens for a view where the width is bigger than the height.

Anssi


Clarification on field of view
#9

Frankly, it sounds like cheating to me. Why bother to take the class in the first place if you’re simply going to fall back on SU’s lightning fast perspective drawing capability?

Why would that be? What is more useful than a view of a model that shows an object exactly as it will appear when built?

I really can’t think of any reason to use any of those obsolete methods except to indulge an antiquarian’s fascination with relics of the past, or unless you’re doing a school assignment for some fossil whose mind is stuck in the 60s.

-Gully


#10

It sounds like cheating to me, too. I’ve never used SketchUp’s FOV or two-point perspective before reading the OP’s question. While I tend to agree with your observation that it (possibly) has no modern relevance, I tried to answer the OP’s question and explain how the FOV relates to perspective in general. As to why someone would want to use it, I suggested two possible reasons in response to your question.

Here’s another opinion:

http://www.renderplus.com/wp2/wk/Rendering_Tip_-_Use_2_Pt_Perspective.htm


#11

Jim, I hope it’s clear here that I am arguing without rancor. It’s just a discussion.

So, okay, I’ve read the Render Plus tip:

Two point perspective, sometimes called ‘2D’ in SketchUp, will keep the vertical lines of
your model parallel to each other. If your rendering software supports 2 pt perspective,
use it for better renderings when ever you are looking up or down on models with vertical lines.

It implies that it is self-evident that having all the verticals parallel looks better or more natural. There is no rationale offered. I don’t agree. If you ask me, between the two examples shown, I think the one with all the verticals vertical looks much more distorted, although the FOV could be cranked down on the full perspective to good effect. It’s almost as if Al Hart deliberately exaggerated the perspective on the 3-point to prove his point, which he didn’t.

-Gully


#12

Using 2-point perspective has usually the same purpose as using a shift lens in architectural photography. It may be called cheating, but it is usually used to prevent a high object like a building looking like it is falling over in a wide angle view. Actually, this “cheating” is what our brain is doing all the time when we move around in the world - your brain doesn’t register any perspective distortion like what can be seen on a photograph even if the actual optical camera in your eye is far from ideal.

Anssi


#13

The “cheating” I was talking about was using SU’s 2-point capability to create a 2-point perspective drawing to trace to satisfy a classroom assignment to draw one–this was @jimhami42’s hypothetical.

Isn’t minimizing aerial perspective distortion as much a matter of dialing in a reasonable FOV for the nature of the object and distance from the camera as it is of 2- versus 3-point perspective?

I was always under the impression that the main virtue of 2-point perspective is that it is faster and easier (within the pokey framework of manual drawing) than 3-point, just as many other simplified pictorial drawing types have been developed where some fidelity is sacrificed for expediency in preparation, notably the axonometric drawing types.

-Gully


#14

2-point perspective is just a special case of 3-point perspective in which the image plane is parallel to some “important” plane of the contents. Pointing the camera that way (or shifting the lens) causes parallel lines in that plane to remain parallel in the image. As @Anssi has pointed out, this has traditionally been done to avoid the phenomenon of “converging verticals”, which the human mind tends to compensate for in normal vision but not in 2D images.

In fact, when you switch to 2-point perspective, all SketchUp does is to rotate the camera so that it is pointing horizontally, which you could indeed do manually.