 So, this is an example on oblique projections. So, we are going to be making an oblique projection of this solid the front view and the top view which is given over here. So, in oblique projections we try to ensure that we show the true features on the plane of the sheet and along the depth direction which could be either 30 degrees or 45 degrees or 60 degrees from the horizontal. We try to show this solid as if it is a three dimensional solid. So, in a sense oblique projection is a nice marriage between orthographic and isometric projections. So, I will draw two kinds the Cavalier projection and cabinet projection. In one of these this depth is the same and in the second one this depth is reduced to half giving an impression of foreshortening. So, if you look at this object carefully they are not many same features. Of course, this is circular feature here, circular feature here semi circle, semi circle joined by two straight lines and then there is a semi circular feature here and these features are to be represented or depicted on three planes. So, I will try to draw the Cavalier projection of this solid first. Once again I will start with the bounding box. The center to center distance is 120 and this distance is about 35 and this distance is also about 35. So, 70 plus 120 would be close to 200 precisely 190. I want to make sure if I draw both of these on one to one scale then I have enough space on my sheet. Let me double check this is 120 and 70 190. Before I start let me align my drafter with the horizontal margin of the sheet make sure that it is aligned properly. Once I align this properly I tighten this screw and I am ready to draw once again I will start with the bounding boxes. So, what I will do is I will sketch these three planes at different depths. So, at depth 0 this is about 190 I am using a 2 H and this is about 70. So, I will mark this here close to the margin should be as close, but I am not really sure if I will have enough space looks like I will to draw the second oblique projection. Nevertheless coming back to the first one this is 90 this should be 70 this should be 90 again. So, I will draw this plane here measure this again this 70 just about close to this point. And then I will use my friend the 30 60 square and to show the depth I will use the 30 degree angle. So, for this one I am going to be using the true depth of 80. So, I will use a longer line segment. So, these are just construction lines let me rotate this measure 80 just about there and then draw vertical let me also draw these depth durations from these two vertices. Since I have already measured 80 from here maybe I just come back and then draw this horizontal and perhaps draw this horizontal at this time they are dim lines you probably may not be able to see most of them, but when we construct the final solid hopefully most of the lines will be clear to you. And then let me have this vertical let me see if I have this thing right just about 80 and maybe this is a little less than 80 I want to be as accurate as possible. So, that I do not make mistakes it is ok for me to use the eraser at this time and hopefully even though I hope that I will not be needing it later. Once no always a good idea to have a piece of cloth with you just to make sure your sheet is clean to get a better view maybe I will use the bottom part of the horizontal scale. Now, this looks about alright and then maybe I will join these two vertices quite a while ago I said that my mini drafter is not accurate and I am just managing maybe I am doing a little better than managing anyhow. So, I have got this plane here and I have got this plane here about this plane maybe I will sketch that I would imagine this is about 20 from here because this is 60 and this is 80 this is about 20 from here. So, maybe I will mark that and once I have made this mark I am going to be using the verticals and the horizontals to identify that plane looks a little better just want to double check this 20 a little deviation, but that is ok then I have got this plane pretty much. So, I have got three planes would it be a good idea for me to start drawing this from the back side or from the front side. So, remember just in case of isometric views I need to show the lines in dark which are visible and I need to show the lines in light graphite impressions which are not visible. So, this feature rather these two circles will be on this plane this feature here will be on the second plane and this feature will be again on the second plane. So, perhaps what I can do is I can draw this feature on this plane because I know that that will be visible and I will draw these two semicircles on the plane behind because I know that they will be visible as well all right. So, having said that. So, let me mark the center lines. So, remember this entire length is this length. So, this is a mental note to myself. So, let me go 35 left from here mark this let me go 35 right from here mark this here well rather there is no point going 35 right from here because these features are on the plane behind this. So, let me mark the center lines over here and this is about 70. So, I will go 35 up. So, before I start drawing these two circles always a nice idea to locate the center well you have to locate the center image here and the center would be on the back plane. So, let me mark the center line let me mark 35 on the back plane and mark the horizontal of the center line rather the horizontal center line all right having done that I will use my compass I will first draw the outer semicircle making sure that I touch both the horizontal edges looks like I do and perhaps this edge also. So, maybe I need to adjust my center there goes my semicircle uniform pressure rather that this would be a full circle. So, let me rather go ahead and complete this. So, a mental note to myself and the others watching this video that this is a cavalier projection. Now, the inner circle is of diameter 40 I do not have that on my stencil. So, maybe I will have to draw that using my compass. So, I just mark 20 pretty much here draw this circle a few times. So, that I get the graphite uniformly impressed on the sheet these two circles done let me take care of the outer semicircle and the inner semicircle first the inner because the radius is something that I know 20 and the outer one which is 35 just make the compass little I think I have got it there would be minor errors, but I will tend to ignore them. So, I got this part right now this distance is 60 measure 60 from here draw a center rather vertical center line maybe I will have a horizontal center line as well a part of it. So, I have got the center for this arc now this arc is on this plane and a part of this arc will be hidden behind this circular feature. So, I will have to be a little careful and I have to draw only a part of it. So, I take my compass readjust the radius to 20 get the center and I will draw only that part of the arc which is going to be visible and I will let go of the other arc. So, I will start from here I will be careful at this part right possibly little distance and perhaps from here up to this part again keeping little distance I do some touching and once I do that I am ready to draw the horizontal lines just want to make sure that I hit the two points it looks like I do and here I hit the two points here as well looks like probably I do little bit of touching. So, I have this feature all set now I have to work this part out for that I need to project the center back or maybe measure the corresponding center from the vertical and the horizontal. So, this is a 35 35 maybe better I would do that use my 2 h 35 and this time I will just be using a dim line this where my horizontal line would be and if I use a 30 60 set square and if I try to project the center line over there I should be able to confirm that it lies on the line which it does. Now, what I will do is I will use a 35 this radius and using this center do I have this center right not sure perhaps going to be this center here of course there would be a little gap on the left anyhow. So, I will draw over a dim you know just to get this tangent 30 degree line once I have that I will use my set square and my drafter assembly go very close to this think about drawing this tangent line I am having a hard time seeing the features from here, but if I hope that I have gotten this right maybe a little lot probably would have at this way touch and then I would know that this part of the arc is visible I will get back to the center and dark on this part of the arc all right now what I would do is I would extend this line up to possibly this position now for that I need to get this part projected over there I will use my 30 60 set square change pencils go up there you know just gently project this point. So, I can extend this line up to this point and of course this feature is tangent to this. So, I know what to do I go on top make sure I do not draw a double line and that is a little difficult at times draw a solid line and right at this position I make a little free hand arc just to give the viewers the impression that this is tangent and I finally make this line all right. So, looks like I have gotten this part right now what I need to do is I need to get this part right and I know that this would be a circular feature here. So, I take my drafter here get the vertical line at 35 maybe with a little thicker line. So, that is visible get 35 from the horizontal mark this get the intersection between these two well they do not need to be that dark just this point is good enough the radius on my compass is set maybe it is not looks like I need to shrink that little bit seems ok seems all right although I draw this part using a light pencil and then search for I do not need to search for tangent over here, but I need to search for one over here. So, this part is little thicker than I imagined it would be rather this part is little darker than I imagined this to be. So, I will erase this part wipe this off first work on this horizontal line which I know will be solid rather dark just want to make sure I do not double line this I come all right there and using my 30 60 square I draw a little oops I should be using a different pencil little line here. So, I know that my curve is going to get truncated at this juncture. So, from here to here maybe I can dark on the circle I have that and then perhaps I can go ahead and dark on this line and a little touch. So, this is my cabular projection of the solid now let me on the side make cabinet projection maybe I can use this part and let you figure the difference between these two. So, what I will do is I will make some preparations and I will ask my friend Astosia to stop the camera to stop the camera the preparations pretty much are the same as this just that this depth and this depth rather this depth they will be halved rather scaled to half. So, this would be 40 and this would be 30, but perhaps on second thought let me go ahead and make all these constructions all over again in front of you. What I would do is I would mute myself. So, that you can just focus on the construction and not listen to the blabbering that I have been doing over you know many minutes. So, I will use this part of the sheet perhaps one statement from my side these depth dimensions they will be halved. So, instead of 80 I would need to take this as 40 and this is 30 one more thing this plane would be at 10 behind this plane. So, like in this case I will have to draw this third plane as well first these two circles this plane the front plane it is a full circle a few rounds and a smaller circle of diameter 20 again a few rounds of this now this feature is on the second plane I need to identify the center for that for the outer circle rather for the inner circle inner semi circle rather I might as well extend the center line to somewhere here this distance is 60 and with the same radius I draw this arc. Now, notice that only a part of this feature will be visible the rest is going to be hidden behind this I just want to make sure that I do not overshoot if I do I will probably have to take help of my friend standing just rather sitting just there looks like I do well not to worry because the next thing that I am going to do is make a larger arc of the same radius as this one looks like I am alright there little touch up. So, next is this semi circle with that center to reduce or shrink my compass a little bit of course these lines are going to get extended up to this here. Let me project this tangent line along the 30 degree direction. So, that I get this corresponding point in the cabinet view possibly here is my first horizontal line switch and pencil just want to make sure that I do not draw a double let me erase this part just a little bit I can always touch it up later well this horizontal line will also be there. So, what this be of course so would this all I need to do is identify these features on the back plane and use the horizontal lines and then I think I should be done with it going back to the back plane identifying the centers identifying the vertical using the dim lines identifying the horizontal this is for center right there and this would be my second one I will get adjusted. So, this is about 35 yeah. So, looks like this is the center taking my compass my radius is all set I think for center here a little to the left perhaps maybe a little more to the left all I need is just this part of the arc again something dim and from here maybe this is where my center was be a little up looks like I am and this part. So, the first tangent here using my solid line and the second tangent here blending let me redraw the rest of the arc may be up till this point can do the touch up later this arc a little darker I realize that there is a bit of inaccuracy here, but so the final touches in this drawing this line was dark already. So, may be a little touch up here and this line was a little dark already we are make it a little darker rather little more dark touch up here and finally, the horizontal line I hope I do not make it a double line there I am little touch up. So, this sheet now is ready let me stripe this object off get the drafter out of the way and. So, this is the Cavalier projection Cavalier oblique projection this is the cabinet oblique projection the height remains the same I will have to get back the height remains 80 the height is foreshortened conventionally to half of 80 spotty just observe the subtle differences in the two views you know a nice thing is that this is as I said fore a nice marriage between orthographic projections and isometric projections. So, if you want to show the circular features pretty much in true scale you would want to choose a plane which is parallel to your sheet yeah here parallel to your sheet and for the depth dimension you might want to choose this angle as 30 or 45 depending on your convenience and get the three dimensional impression to this solid. So, well if I ask you which one is looking more three dimensional it is up to you to observe and then tell yourself for me possibly this because this has little foreshortened feature, but this is also alright I mean just imagine that if you have this depth to be 160 then this would rather be a cabinet projection for this depth to be 160 and this depth to be 120 I believe. So, observe the differences while I leave you for today and come back with perspective projections later in the next lab.