'Orthographic drawing' refers to a 2-D representation of an object in a view that shows only one side at a time. Most orthographic drawings occur in multi-drawing sets in order to depict each side, top and bottom view. Professions in design and construction use these types of drawings to inform the. Of a three-dimensional object. Each orthographic view is a two-dimensional drawing showing only two of the three dimensions of the three-dimensional object. Consequently, no individual view contains sufficient information to completely define the shape of the three-dimensional object. All orthographic views must be looked at together to. Orthographic views are two-dimensional drawings used to represent or describe a three-dimensional object. It is important to engineers so that you can see the object in different perspectives.
In risk of being off topic for broadness and discussioness.. but I think in the end it's a question that can't be avoided.
Can someone please finally explain the difference and why we need both?
JNFJNF5 Answers
$begingroup$Orthographic is commonly used in engineering as a means to produce object specifications that communicate dimensions unambiguously, each line of 1 unit length (cm, meter.whatever) will appear to have the same length everywhere on the drawing. This allows the drafter to dimension only a subset of lines and let the reader know that other lines of that length on the drawing are also that length in reality. Every parallel line in the drawing is also parallel in the object.
If you are looking at a larger scene with buildings then orthographic rendering gives a clearer measure of distance between buildings and their relative sizes.
With perspective mode lines of identical real-world lengths will appear different due to fore-shortening. It becomes difficult to judge relative dimensions and the size of objects in the distance.
While modelling nothing stops you from switching between orthographic and perspective mode to get a better sense of the object.
zeffiizeffiiOrthographic is (according to Wikipedia):
.. a means of representing a three-dimensional object in two dimensions..
Bascially, Orthographic is a fixed depth. You can't zoom in or out. There is no distance from the camera.
Perspective has depth. You can zoom in and out. You can judge distances. Cameras can be distanced from the scene.
Simply put, orthographic is what would happen if you squished everything in the scene (along the cameras view axis) and stuck it right against the camera.
Perspective on the left, Orthographic on the right
CharlesLCharlesLOrthographic view is a view that is not real world. It virtualy displays objects, such as a cube, in a way that it can be seen with out a paralax error. Paralax error is where you can see an object from a certain angle and it look like it is the same height as another object. Optical illusions take advantage of this concept. To clarify, if you were to stare at a clock in orthographic view you would see every thing lined up perfectly, no paralax error, you can see clearly, exactly what time it is. If you looked at it from Perspective you would be able to see under the hands, and if look at from a different angle other than head on you would see a different time other than what it really is.
So Why do we need those views?
Well, say you are creating an architectural visualization, and you needed to ensure that two sides of this building were exactly the same height. If you were in perspective you could look at it from any number of angles and it would appear even. But if you were in Orthographic you would be able to see it without, parallax you would see it straight on virtually no dimensions except for up and down, and left to right. This way you would be able to see that oh, they are not really lined up, or that they are. Hope this helped!
Owen PattersonOwen PattersonOrthographic - This is without perspective distortion. I use this when modeling. You can model more accurately, and align things in the scene easier.
Perspective - It will change depending on the 'focal length' you use for the camera when rendering or during animation, so this is best not used when modeling, but it can help you get a feel for the object while modeling.
Ok. It is pretty much everyone said but with an example. (Correct me experts if I am wrong).
Imagine you are standing on a middle of the Train Tracks facing the direction of the track and looking as far as you can on the origin of Track. (Imagine without train as well :) ).
Track looks like it is coming from a single point in your PERSPECTIVE. (http://www.animationbrain.com/one-point-perspective.html)
But Orthographic(ally) they are parallel lines as everyone knows.
protected by cegatonSep 21 '15 at 16:25
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3-2 ISOMETRIC DRAWING |
| 3-18 CREATING ANIMATIONS IN AUTOCAD |
Topics covered in this Lesson:
Isometric Drafting Techniques
ISOMETRIC DRAWING
Using Isometric commands is one of the simplest ways to give a 3-D representation while using only 2-D commands. This has been the usual way of doing things before CAD allowed true 3-D work to be done. Many times an isometric drawing is used to compliment or give more information to a 3 view orthographic drawing. See the sample below.
You can see that it is a very simple drawing. This basic isometric drawing of the object gives a very good idea of what it looks like. If this is all that is needed then isometric works well. Unfortunately, as soon as you change anything, like the block's height, you'll need to redraw all four views.
AutoCAD has a command called ISOPLANE which allows you to easily draw at a 30 degree angle as needed for an isometric drawing. You can switch between the three 'isoplanes' (top, right, left) by using this command or by pressing the F5 key.
Command: ISOPLANE <ENTER>
Current isoplane: Right
Enter isometric plane setting [Left/Top/Right] <Left>: T <ENTER>
Current isoplane: Top
Newer versions of AutoCAD have an Isoplane icon on the status bar. You can click this to enter Isometric Drafting Mode as shown below. You can also change your Isoplanes here (but F5 is faster).
By invoking this command, AutoCAD is now set to draw on the top isoplane by default. Your other choices would be Left or Right. Your first exercise will be to draw the object shown above using isometric methods.
Exercise 1 - Isometric Drafting
Begin a new drawing using the acad.dwt template
Create a layer called OBJECT and give it a green color. Make this your current layer.
Type in DDRMODES to bring up the Drawing Aids dialog box. Make your settings the same as what you see below (just turn on Isometric Snap).
NOTE : Remember this dialog box for later. When you are done with Isometric Drafting, open this dialog box again and change the radio button from 'Isometric snap' to 'Rectangular snap' to get back to the regular drawing settings. |
Press OK and you'll see that the grid is set up for isometric drawing for the left isoplane in 1/2 unit increments. Your crosshairs are now angled to show you which isoplane you are currently on and the Grid is laid out differently from what you may be used to.
Begin by drawing the left side of the box (shown at the top of the lesson) using the line command. Ignore the hole at this point. You will want to use the Direct Distance Entry System for this exercise and make sure that you have Ortho (F8) and Osnaps (F3) turned on.
Switch to your right isoplane (F5) and draw the right side.
Switch to your top isoplane (F5) and draw the top view.
Create the angle lines to add the angled surface.
Switch back to the left isoplane and start the ELLIPSE command. At the command prompt, press I for isocircle. This will allow you to create an ellipse at the correct angle based on the radius of the circle in the orthographic drawing. Use the Osnap to pick the correct center point.
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Save your drawing in your CAD folder. (You have a CAD Folder by now, right?)
To dimension an isometric drawing, you have to do a few things first. Create a text style called Left, and give it a 30o obliquing angle, then create another called right with a -30o obliquing angle. Then create a new dimension style that has the text aligned with the dimension line. After you have placed a dimension, use the DIMEDIT command to change the obliquing angle of the dimension + or - 30 degrees. You may also need to use the properties to change the text in the dimension to left or right depending upon the orientation of the dimension.
Keep in mind that this is still only 2D. Remember that in some instances, it may be quicker and easier to use this method rather than the more complex 3-D methods you'll be learning in the following lessons.
Extra Practice: Copy this drawing using isometric drawing methods.
Extra Practice: Copy this drawing using isometric drawing methods. If you want to add the hidden lines, jump ahead to Lesson 4-3 to learn about linetypes.
Autocad Orthographic View
Even More Practice: Try to reproduce these drawings. (Also keep this link bookmarked for when are looking for practice in 3D techniques.)
Video: Isometric Drafting
Autocad Orthographic View Tut
Take the Lesson 3-2 Quiz
For Further Thought:
Although this is still a 3D representation in 2D, you are already taking steps to 'think' in 3 dimensions. This is important and you will continue through these tutorials learning 3D AutoCAD techniques and performing them on a 2D monitor. Organizing your drawing with layers and 'seeing' and thinking in 3D takes practice, skill and sometimes a lot of patience.
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