Am 02.05.2010 16:43, schrieb POV-Zhstar:

> scene by POV-Ray. Because the field of view of the camera is 25 degrees and
> POV-Ray uses the reverse ray tracing (rays are sent backwards from the camera to
> the light source), then I thought the output scene should be a circle for this
> case (camera vertically sees the object plane), ellipse otherwise. But the

> this. Could someone explain the reason? Thanks!

The "angle" keyword is intended to be used for "zooming" in on an image 
without having to fiddle with the other camera parameters - and that's 
all it does. The value you specify here will be the /horizontal/ opening 
angle of the camera frustrum, which will remain pyramidal in shape 
(typically with a rectangular base) at least with the standard 
perspective camera, i.e. the image will remain rectangular.

If you need a circular-shaped image, you'll need to post-process it in 
your favorite image manipulation software.

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POV-Zhstar wrote:
> I use the camera by setting the keyword ‘angle’ of 25 d
egrees, and generate a
> scene by POV-Ray. Because the field of view of the camera is 25 degrees
 and
> POV-Ray uses the reverse ray tracing (rays are sent backwards from the 
camera to
> the light source), then I thought the output scene should be a circle f
or this
> case (camera vertically sees the object plane), ellipse otherwise. But 
the
> POV-Ray output an image of rectangle in shape. I can’t understa
nd why it is like
> this. Could someone explain the reason? Thanks!
> 
	I'm not sure why you would expect it to be circular or elliptic.
There is a drawing explaining the camera field of view and the
camera parameters on this page:
http://povray.org/documentation/view/3.6.1/246/

		Jerome
-- 
mailto:jeb### [at] freefr
http://jeberger.free.fr
Jabber: jeb### [at] jabberfr

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clipka <ano### [at] anonymousorg> wrote:
> Am 02.05.2010 16:43, schrieb POV-Zhstar:
Thanks!
> The "angle" keyword is intended to be used for "zooming" in on an image
> without having to fiddle with the other camera parameters - and that's
> all it does. The value you specify here will be the /horizontal/ opening
> angle of the camera frustrum, which will remain pyramidal in shape
> (typically with a rectangular base) at least with the standard
> perspective camera, i.e. the image will remain rectangular.

Oh, I thought it was in conical shape, which caused my puzzle.


> If you need a circular-shaped image, you'll need to post-process it in
> your favorite image manipulation software.
Thanks. Could you give some suggestions about how to get such circular-shaped
image?

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=?UTF-8?B?IkrDqXLDtG1lIE0uIEJlcmdlciI=?= <jeberger@free.fr> wrote:
>  I'm not sure why you would expect it to be circular or elliptic.
I want to see the rendered regions specificly of my camera with a prescribed
field of view in a conical shape.

> There is a drawing explaining the camera field of view and the
> camera parameters on this page:
> http://povray.org/documentation/view/3.6.1/246/
Thanks! It helps a lot!

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Am 03.05.2010 05:42, schrieb POV-Zhstar:

>> If you need a circular-shaped image, you'll need to post-process it in
>> your favorite image manipulation software.
> Thanks. Could you give some suggestions about how to get such circular-shaped
> image?

Open image in your favorite Photoshop/Gimp/Whatever, mark a 
circular-shaped area, invert the selection, cut away (make sure your 
current layer allows for transparency; e.g. in Photoshop you may need to 
duplicate the layer first, then discard the background layer).

Export the image with transparency (aka alpha channel), and you're there.

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clipka <ano### [at] anonymousorg> wrote:

> If you need a circular-shaped image, you'll need to post-process it in
> your favorite image manipulation software.

Or put a hollowed out black cylinder in front of the camera

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"jhu" <nomail@nomail> wrote:
> Or put a hollowed out black cylinder in front of the camera

Your method seems to can do. Could you elaborate it? Sorry I am a new user:)
Thanks!

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> "jhu"<nomail@nomail>  wrote:
>> Or put a hollowed out black cylinder in front of the camera
>
> Your method seems to can do. Could you elaborate it? Sorry I am a new user:)
> Thanks!
>
>

Try this:

union{
camera{location 0 look_at z}
cylinder{0, 10*z, 3 pigment{rgb 0} open}
rotate Some_Direction
translate Some_location
}

This create a camera identical to the default one, and link it with a 
cylinder with an union. This enable you to rotate and move both toggether.
The open keyword removes the ends of the cylinder.
Lastly, you use rotate and translate to orient and locate the camera as 
you want to.
If you want an elliptical opening, just unevenly scale the cylinder:
cylinder{0, 10*z pigment{rgb 0} open scale<4/3,1,1>}


You can also try with the fisheye camera. That camera will render a 
circular image, if the hight and width are the same.


Alain

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Alain <aze### [at] qwertyorg> wrote:
> Try this:
>
> union{
> camera{location 0 look_at z}
> cylinder{0, 10*z, 3 pigment{rgb 0} open}
> rotate Some_Direction
> translate Some_location
> }
>
> This create a camera identical to the default one, and link it with a
> cylinder with an union. This enable you to rotate and move both toggether.
> The open keyword removes the ends of the cylinder.
> Lastly, you use rotate and translate to orient and locate the camera as
> you want to.
> If you want an elliptical opening, just unevenly scale the cylinder:
> cylinder{0, 10*z pigment{rgb 0} open scale<4/3,1,1>}
>
>
> You can also try with the fisheye camera. That camera will render a
> circular image, if the hight and width are the same.
>
>
> Alain

Thanks! This should what I want. I tried just with your method. But it shows the
following error:
Parse Error: No matching } in 'union', camera found instead
But I am sure there is no missing "}" in the scripts. What's wrong?

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POV-Zhstar wrote:

> Parse Error: No matching } in 'union', camera found instead
> But I am sure there is no missing "}" in the scripts. What's wrong?

I don't think you can use a camera in a union:

UNION: union { UNION_OBJECT UNION_OBJECT... [UNION_MODIFIERS] }

UNION_OBJECT: OBJECT | LIGHT

Alain was probably thinking of a light_source, which
you actually *can* bind to geometry in a union.

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