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real projector Vs C4D camera


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#1 Guest_defaultfx_*

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Posted 03 September 2010 - 12:46 AM

I am doing some tests in projection mapping, mapping physical geometric shapes with content created in C4D.
Question is this -
How do I sync my projector specs with the C4D camera to ensure my mapping in c4d fits with the physical shapes I have made in real space?
Here are the specs of my projector and I cant make sense of these within the virtual environment.
if anyone can point me in the right direction as to how to tally these with my camera, that would be great!
projection image size - adjustable from 33" to 300"
throw distance 4.3' - 32.8' (1.3m - 10.0m)
projection lens F1.7 - 2.1 lens with with f26.7mm - 32.0mm

JB

#2 oldmanboy

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Posted 04 September 2010 - 02:43 AM

Hey defaultfx,

welcome to the cafe.

I dont usually work with projector specs. But I would imagine the following will solve your problem:

I think you need to focus on the aperture, focal length and throw distance first. Out of this should come your image size by scaling the image and what not.

So create a camera and go to object tab. set focal length as per above ie. between 26.7 - 32mm (check what you have set on the projector), set the aperture to f1.7 - 2.1 (again check the settings on the projector)

Create your object and move it off center by your throw distance (4.3' - 32.8')

all the above should give you the right size. You may need to scale either the texture or the object that its being projected on or both.

Hope that helps

D

#3 Guest_defaultfx_*

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Posted 04 September 2010 - 08:09 AM

Thanks for this . .
SO do you think If I adjust my focal length to 32 - which is lens wide open and adjust my aperture width to 30.6 which I think is equivalent to 1.7 aperture wide open ( using this math that I found on the forum - @stevemacc 'The defaults in C4D are a 36 Focal length and a 36 aperture diameter, which is an f-stop of 1. If you made the diameter 18 you would get an f stop of 2.')
My link
Do you think that would be technically correct to start working on my mapping confidently ?
Still a little confused about the throw distance tho' I am expecting to position my projector some 8 metres away and 5metres high from the shape so I should be OK..
thanks
JB

#4 oldmanboy

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Posted 04 September 2010 - 11:17 AM

You are headed in the right direction except your maths is off.

If you have a focal length of 32mm and want an aperture of f1.7 thats 32/1.7 = 18.82352.... So an 18.8mm aperture or there abouts.

Try that out and let me know how it goes.

What is the project you are working on if you dont mind me asking?

D

#5 Guest_defaultfx_*

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Posted 06 September 2010 - 02:18 AM

Well its been a tricky but in the end I created a group object with camera and projector screen (plane )at the size stated and at the distance apart, I squared it up so that the projector meets the size of the plane and I am now using this as a template. so all should work fine. The maths just didnt appear to be working correct! its for an art show in Dundee, I will post to the board when its nearer the time, invite y'all.

#6 oldmanboy

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Posted 06 September 2010 - 02:44 AM

Cool mate.

Its definitely another area that C4D needs to work on. The only thing they added in this for r12 is color temp and white balance. I personally dont know any photography who works in mm for their apertures. As if they could be asked calculating that out anyways. :P And its weird that aperture messes with field of view, On a camera it determines how much light hits the sensor.

Anyways, Let me know what that art show is all about. I'm in edinburgh and mayhaps come and check it out.

D




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