 Today, I will introduce you to God all right. So, let us get started a familiar figure. So, let us say have a plane in front of the object on the side and the back on the top the rays from the object come out to the plane. You get the front view likewise you get the top view or the plan view and likewise you get the right hand side view something that you have seen before. If you flip open these planes about the hinges you get the third angle projection something that you have seen your frontal view happens to be in the third quadrant and I said well I mean if you are working with three views the front view the top view or the plan view and the profile view which is the right hand side view in this case. If you are working with three views and if it so happens that your frontal view happens to be in the third quadrant it is third angle projection same thing, but in this case now the plane is at the back bottom and on the left hand side you let the rays emanate from the object and let them fall on these respective planes you get the front view here you get the plan or the top view here and likewise you get the side view there. Again if you rearrange these planes your frontal view happens to be in the first quadrant. So, remember that you are working with three views frontal top and right side view not the left right side view and then I said that well in this case of your frontal view happens to be in the first quadrant then this is the first angle projection and then my colleague Prasakishore he visited me and he was like well if I remember correctly I learnt it slightly differently and then I have to jog my memory back well back in 91 did I learnt same way or maybe I learnt it differently. So, and then I said yeah possibly I learnt it differently I had doubts. So, in life when questions bother you then you already seen God right why do you say no to that you either refer to your Bible your text and just in case if you are not used to referring to your Bible you pray you pray to God you may not be able to connect with the real God in a sense that of course I mean you may be speaking to him or her ok, but you may not be hearing his or her voice back, but this guy will try to come up with an answer ok. The answer may not be the one that you are looking for, but still it will try to be as close as possible to the answer that you are looking for. So, I did the same I had doubts I had doubts I went to my God and I type a few things and this is what it came up with different sources and I am going to be reading this text first angle projection is like keeping a solid in front of a screen and seeing it from the other side of the screen. If I am the object I am in front of the screen, but I have to go back to look at myself from behind the screen that is what it says the first angle projection is from answers.yahu.com, but it is not quite right and that is the reason why I have marked this text in red seeing it from the other side of the screen. If I am standing here and if I if an image of mine if an instance of mine CSC 101, if an instance of mine goes back and looks at myself from behind the screen ok, what will that instance of mine see my back side the mirror image which is not quite right fine. It is just projecting all the edges points features etcetera over a plane that is behind the solid which is something that we have been doing which is ok. Second source this is from Wikipedia in first angle projection the projectors originate as if radiated from a viewer's eyeballs ok and shoot through the 3D object to project a 2D image onto the plane behind it and just reading. In third angle projection the projectors originate as if radiated from a 3D object itself and shoot away from the 3D object to project a 2D image onto the plane in front of it something that we have been doing ok consistent perfectly consistent, but from where does the first angle and the third angle these names come from not so very clear. So, I was not satisfied ok I kept asking God and then I got something in first angle projection the object is conceptually located in quadrant 1. Now, here is where the difference lies. So, what I told you before was it was the front view that was located in the first quadrant, but this guy says that is the object which is located in the first quadrant ok like subtle difference i.e. it floats above and before the viewing planes the planes are opaque and each view is pushed through the object onto the plane furthest from it and then it is talking about the projections ok same thing that we have been doing well if you are not able to understand the text it is perfectly fine I have a graph. Imagine the space divided in 4 quadrants quadrant 1 2 3 and 4 you see the frontal plane you see the horizontal plane and you see the profile plane ok quadrant 1 2 3 and 4 frontal plane horizontal plane the right hand side plane or the profile plane ok. So, if you keep this object in quadrant 1 and this is the important point if you look at this object from the right this is the important assumption if you look at this object from the right that means from here if you look at this object from here and if you let the projections emanate from this object and get back onto the frontal plane what would you get what would you get louder front view likewise if you let the projections emanate from this object and hit the horizontal plane flip it over what will you get the top view ok and if you let the projections come out of this object hit the profile plane what you get which profile who said left who said right which one is right which one is gotta be careful where are you looking so where you standing with respect to the object left hand side or right hand side you are standing here you are standing here what would you get on this profile plane left so this is where the nomenclature comes from ok, but if you realize you are smart if you realize if you are in the first quadrant and if you open up the views you will be essentially getting the frontal view in the first quadrant similar subtle difference ok one thing that you need to remember again is in this nomenclature you have to be standing or you have to be looking at the object from the right ok in third angle projection the object is conceptually located in quadrant 3 forget the rest of the text look at the car ok once again you are looking at the object from the right once again you are looking at the object from the right you are standing here ok, but it is this plane which is intercepting your view in a sense that this plane is in between the object and yourself ok you do the same exercise you get the front view you get the top view or the plane view and then you get the right hand side view flip it open what you will be getting would be the third angle projection once again in there if you are looking at three views front top and right FTP ok your frontal view will be in the third quadrant ok there is this anecdote which is again philosophical with respect to ta 101 you have to have an eye for the drawing that comes with practice that would not come straight forward on a plate wave it comes to practice you have to have an eye for the drawing ok if you do not have it develop it ok and that is the reason why I call this course think and analyze I encourage you to make mistakes like I do I will tell you about some of my mistakes that I did which you have absolutely no idea about ok I encourage you to make mistakes because that is how you learn that is how you develop the eye you make mistakes you realize that you have made mistake and then you say well fine next time when something similar happens I will not try to make a mistake or I will not try to repeat the same mistake ok I encourage you to make mistakes and learn from it for example you must have done this problem in lap 2 what is wrong with this ok even I did not realize until what is your name Shreya mentioned that there would be a line here ok there would be a line here would there be would there not be because that represents the line of intersection between two planes the plane at the bottom the plane the plane here and the plane here do you agree or do you disagree agree or disagree good ok first mistake which went this is the problem that you are doing currently so people in Monday's badge and people in Tuesday's badge ok they are working on that well the dimension is not there so you can assume the dimension to be 10 so for those who have done this problem they may have assumed this dimension to be 10 for those who do not take it as 10 but this is not what I am referring to I am referring to something more fundamental which Shreya pointed me out pointed out to me she is one of the tutors in Monday's batch right Thursday's batch ok watch carefully do you see any mistake in this you do what is it one extra solid line which is where where is it front view this one no but this one are you are you referring to this one yeah any other mistake this line should it be there should not be there ok these are subtleties and which is very very difficult to kind of keep in mind ok it is very easy for us to miss out on these subtleties ok and which are for the what circle this thing should be equidistant from where it is not from here and here you mean this one ok so third mistake ok so the point of emphasis is that you have to develop and I for the drawing and I am so very glad that you are pointing these mistakes out helping me learn and helping yourself so in this solution for example there was a mistake that I realized just today which is what ok so in the solution that I had discussed in the previous class I had shown this line ok this line would not be there ok so there was this discrepancy I may have said something else in class and you guys when you are when you are doing the lab you probably read the question slightly differently so let me clarify that when I ask you to use isometric scale I would do that when I ask you to work with isometric projection of view ok so isometric scale is something that you need to you need to be using when you are drawing isometric projection of view ok but you are going to be using the true scale when you are drawing the isometric drawing I probably may have said the other way around in this class last time right yeah ok so today it is about missing lines and views to help you develop an eye for the drawing I want you guys to open up your sketch books and pens and start working with me 1 is to 2 by root 3 under root 2 that would be a smart way of ignoring the isometric scale wanted huh wanted yeah so I do not expect that let us take a look at this set of views third angle projection draw them in your sketch books quickly this is where this is where you will also hopefully appreciate the importance or import of pictorial view or isometric drawings ok so let us say this is the object and somebody asked me a question here yeah so something which is of importance to you now is this correct let me quickly draw the basic projection or construction lines ok now I am trying to rectify these drawings I look at this point here ok in section 2 lines I look at this point here ok if I project this point on to the plan view or top view I will see something ok and if I project this point on to the right hand side view I will see something ok if I have a point in one of the views what would I see in the other 2 views lines lines huh and are they going to be perpendicular to the hinge lines or are they going to be parallel to the hinge lines they will be perpendicular to the hinge lines ok I take look at this point I project this thing upwards I take a look at the corresponding image of this line this this point over there which is a line in the right hand side view ok so what do I expect there in top view straight line horizontal vertical slanted good ok simple exercise of correlating different features in different views which you would soon realize it is not that simple ok so I want you guys to be with me and glue your eyes on to the screen one eye to me the other one to the screen ok how about this point here what do I expect to see just a portion of the vertical line I expect to see only a portion of the vertical line why is that because if I took a look at the image of this point in this view ok I see only a portion of this line ok I do not see the entire line but only a portion of this line ok so I project this line upwards on to the left to the top view and then I get this good enough ok what do you propose I mean I am not saying that this set of figures is complete now ok now look at this point here image of this point in this view is a horizontal line ok what do you expect look at this point here image of this point in this view is again a horizontal line what do you expect there am I done yet yes would I see a line here here done how would my object look like how would my object look like can you figure not straight forward possibly if you sketch it out your object will look like this agreed agreed ok still thinking ok example two let me quickly draw these construction lines so I am not showing these construction line because they are quite obvious I am not showing these lines ok they are quite obvious so the idea is you look at the three views you look hard you look harder and then you try to figure which of the features and which of the views are not related ok for example this guy here ok this point here you do not see the corresponding image in the front view or possibly in the side view ok what do you expect here no no so let us let us break it down so lines and rectangles so what do you actually expect here a line yes no horizontal vertical this is the slant line here the image of this slant line here would be horizontal huh convinced always always not always when this case maybe it is so you see a vertical line you will see a vertical line and you will see horizontal line ok rectangle some few had mentioned that is that it is that it this is how the object is going to look like ok this one let me quickly draw projection lines again construction lines ok this feature here is related to this point on the right side view this dotted line in the top view is related to this point here at the bottom so far so good no changes in the three views how about this guy a point image of which would be a horizontal line here go up you already see a horizontal line here ok this would be a solid line how about this guy here dotted line is that it this is how your solid is going to look like in pictorial view pictorial sketch ok so try to realize what I am trying to do here so I am just working with the three views given to me ok and what I am trying to do is I am trying to correlate different features and different views with other views ok ok and then once I figure that ok fine I cannot go any further from there and I assume that the three views that I have constructed are ok and are correct ok and then I attempt to sketch this three dimensional solid ok but this approach is not always applicable as in this approach will not always work ok you will have to draw the pictorial view as in when you are making revisions to your orthographic views this one for example so I need your help in this one work it out 2 minutes think about that and tell me which features are missing in which views ready yes no ok how about this point here what do you expect a part of it would be a line a part of this vertical line would be a line which part ok I go from the right ok this part would be a line what else there would be a horizontal line and this would correspond to what so you are suggesting that there would be a line here horizontal line here and this would be the image of which feature in this view this arc ok complete horizontal line let me address this point here ok so this is in section point here would they be a vertical line yeah yes or no ok would this part of the line be there and then somebody says that there would be a horizontal line is this how your solid is going to look like small mistake ok where are we called suggest that there should be a line here you sure thinking you sure are analyzing and I am very happy about that which is what I want you guys to ok those who say no those who say no raise your hands and can somebody stand up and tell me why it is a smooth curvature it is this there is no region of discontinuity in surface so you say that this it appears to be like that who says yes ok come up come up come up what sort of says is this since there is a line here there should be a line here did I did I get right ok is he right is he correct what is this line signifying line of section between two surfaces which ones this plane here and this guy here right so there is a line here would there be a line here who disagrees from here to here so the two parts one part is getting truncated over here ok corresponding to which there would be a line here ok the other part is going straight out and it is getting truncated over here ok so this arc folks try to understand this so this arc emanates from here gets truncated here ok goes flat and that constitutes this horizontal surface ok other part of it goes up over here gets truncated over here and that corresponds to this plane here ok so there would be a line here I am allowed to make mistakes if I do not make mistakes many of you guys will be dozing off by now the fact that I make mistakes keeps you guys vigilant and active right around ok this is tricky and what is your name yeah Chirag your question will be answered now this is an example where just correlating different features in different views will not help you will have to draw the pictorial view of the object I will need some more time I will need about 10 15 minutes ok now this is what we will do I won't say anything from now ok you will just see a line either a gray line or a dark line on your screen and you have to say yes or no ok ok yeah it goes yes or no ok assuming that is a yes assuming that it is a yes if this is a yes then these two lines are possibilities these two lines are possibilities then this is how your solid will look like ok let me retract these steps Chirag and others line number one line number two line number three if I draw these three lines I get to see a solid which looks like this ok however if I draw this line instead then I do not need these two hidden lines in which case the solid is going to look like this ok in case one I had to work with three lines in the second case I can just work with one line so there are multiple possibilities ok but the understanding is that you have to work with minimum possible number of lines ok this is what the understanding is minimum there is one more one more possibility with the same number of lines ok ok yeah our vehicle has another vehicle now all three should be complete all three should be complete assuming that the three no no what is given to you it is ok but again all three projections they should be complete assuming that the three projections are uniquely representing a solid all three should be complete and how do we know you have to develop a nine minimum possible lines are to be introduced this is the unsaid understanding unsaid statement I can introduce theoretically I can introduce the square here a square there a square there and get a block I can do that I can do that as many number of times as possible nobody stops me from doing that ok but then I am not looking at multiple possibilities I am looking at folks so guys in the CSE there are two things happening in parallel ok there are two things happening parallel one is a vehicle is sharing another vehicle with you and second is I am speaking with Unshuman ok and I want you guys to be polite and patient ok so can you take a seat curved plane to address Unshuman and the rest of you once again the understanding the unstated understanding is you have to work with minimum number of lines adequate enough to complete all the three views ok and to address another vehicle of a vehicle this is a plane this is a plane defined by four points which are coplanar or not they are not coplanar a plane is defined by three points it is a warped plane twisted yeah warped yeah that is that is that is something which is not allowed ok so something that you need to keep in mind something that you need to keep in mind try to avoid these possibilities because this is a plane which Avikal says it is warped these four points they do not lie on the same plane ok it makes sense because it is three points that define plane uniquely ok yeah what is the principle ok so Kevin I will are you guys with me so far who is not who is not with me so far everybody with me I will answer this question later after class let me proceed ok it does help if you are drawing the pictorial view of the object alongside when you are in process of correcting the three orthographic views this one once again I will start drawing all you need to do is give you a consent or give you a descent descent descent say yes or no ok good enough ok so try to figure out the drawing later on I mean try to figure out the object later on this one is quite straight forward quite straight forward so you have given you have been given the front view two squares as the top and the right ok do not think loudly do not think loudly just say yes or no stay with me yes yeah solid hidden solid hidden what are you saying what are you saying I am lost I am not with you you are with me I am not with you what are you saying again this thing ok ok alright so are you with me centerline do not miss out on even the center lines when you are completing your views this example is there on the web page so if you want to take a look ok so I am done thank you.