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Topic ClosedAuto Cad & Solid 3D Geometry

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Rikky View Drop Down
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Joined: 30.Jul.2010
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Direct Link To This Post Topic: Auto Cad & Solid 3D Geometry
    Posted: 29.Nov.2010 at 09:13
Just try perspective and than 1 en it will be what you would have... You can also change the view of the perspective at the view panel.
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Hana.A View Drop Down
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Direct Link To This Post Posted: 28.Nov.2010 at 01:38
A question cad64
can I draw a pyramid out of triangle by hand?

I mean away of using the 3D programs

---------

well when you do ask about he numbers and measurements do you want the lengths ?

yes the model is same dimensions / ratios of the one i draw on autocad
Hana
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Cad64 View Drop Down
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Direct Link To This Post Posted: 28.Nov.2010 at 01:27
Sorry but a picture is not enough proof. If you're going to claim that the actual dimensions of the object are changing then you need to provide proof of this by taking measurements. But I can guarantee you that the dimensions of the object are not changing. It's just the visual display that is distorted because the perspective on screen is not the same as the perspective of the object in your hand.

Do as I suggested and add a camera. View the object through the camera and play with the lens length.

I assume you created the pyramid with the exact same dimensions as the one in your hand? Same base dimensions and height?


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Hana.A View Drop Down
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Direct Link To This Post Posted: 28.Nov.2010 at 01:05
Hello Cad64,

i do researches on the 3d geometry.

if you want numbers this wont help in any thing when its 3D model 'imo'!!
only the picture i show you is enough proof of dimensions and angles change. cau if u stick 3 edges of the model on your hand on 3 edges on the model on the screen other 2 edges at least one of them have to be matching.

it  was hard for me to hold the camera in hand and other hand holding the model o here is a little unadjusted placement of the model on my hand on the image on the screen.


Hana
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Cad64 View Drop Down
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Direct Link To This Post Posted: 28.Nov.2010 at 00:41
Ok, first of all, can you please tell me why you are doing this? Why are you trying to match up a physical model with your image on screen? What purpose does this serve?

Second, I am still waiting for you to give me some numbers. You keep saying the dimensions are changing but you refuse to provide any proof of this. If the dimensions are changing, which I don't believe they are, that's a problem. But if it's just a matter of the display not lining up with your model, maybe you should place a camera and play with the lens length and see if you can get everything to line up.

By the way, it doesn't look like the wolfram mathematica lines up either.


Edited by Cad64 - 28.Nov.2010 at 00:49
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Hana.A View Drop Down
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Direct Link To This Post Posted: 27.Nov.2010 at 23:19
Hello Cad64,

I had Autocad 2009 on my machine before I format it, I just got the disk today and installed it already

please view the attached example

first picture of wolfram mathematics and on any rotated position I put my model front the screen and its fit the model  on the screen.
in autocad 2007, 2009 show mess even the perspective view mode is on.

 http://htam.info/cad.jpg
Hana
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Cad64 View Drop Down
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Direct Link To This Post Posted: 27.Nov.2010 at 01:57
So you don't even have Autocad? Why are we having this discussion then?

I think you are confusing your terminology though. You are stating that the dimensions of the model are changing, but I don't think that's what you really mean. I think it's just a case of the perspective view on screen not matching the object you're holding in front of the monitor. If you turn on Perspective, in Autocad, I think the screen display will more closely match the object you're holding. But you should not expect it to be a perfect match. Remember that you are holding a real 3 dimensional object in your hand and trying to match it up against a 3D representation on your flat screen. It may not be a 100% perfect match.
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Hana.A View Drop Down
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Direct Link To This Post Posted: 27.Nov.2010 at 00:40
Thank you cad64 for explaining

yes I mean by eye mapping ( perspective) model on my hand and the monitor in the back side of the model.

well my dear I will get the CD of auto cad today or tomorrow from a friend , I will install it and take picture to explain what I do mean






Edited by Hana.A - 27.Nov.2010 at 06:35
Hana
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Cad64 View Drop Down
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Direct Link To This Post Posted: 27.Nov.2010 at 00:12
Originally posted by Hana.A Hana.A wrote:

The dimension change
maybe i have no so much experience with auto cad but what more than a Engineer friend of mine who I discussed with him the matter and he said its first time to notice this and he was surprised , i think there an option in autocad on the lower bar to lock the dimension of the shape and he did click but still with rotation the dimensions lengths get so different than reality.

what I can do for you to proof this is to take photo of my camera to show you the clear different

but let me ask you question first... if you have for example pyramid shape and you eye mapping 3 edges on the same dimension pyramid on your screen, the other 2 edges of the pyramids on your hand 100% of the model on your hand will lay on the shape on your monitor on any position this how its.
im going to prove it for you soon
 


Please provide me with numbers. You keep saying that the dimensions change but you have yet to give me any proof of this. What are the dimensions of the object before rotation and what are the dimensions after rotation? I just tried it on my machine, and no matter how much I rotate the model, the dimensions never change. They stay constant. I have been using CAD and 3D programs for well over 20 years and I have never experienced anything like what you're describing.

You also keep saying "eye mapping". What in the world is "eye mapping"? Are you holding a model in front of your monitor and trying to match it up with the screen display? If so, why?

The only thing I can think is that you don't have Perspective turned on. But even then, the dimensions will not change after rotation. This is what I don't understand, so please provide numbers. What are the dimensions of the model before and after rotation.
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Hana.A View Drop Down
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Direct Link To This Post Posted: 26.Nov.2010 at 23:55
Hi Ricky

I will be sure to try this again after re install autocad

thanks
Hana
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