[Bf-committers] DOF camera parameters.

[Matt Ebb]

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On 10 Jun 2004, at 5:33 PM, Jonathan Merritt wrote:

> As part of the Aqsis RenderMan exporter that I've been hard at work on 
> over the last two weeks, I've added some new parameters to the Blender 
> camera:
>    1. Focal length ("internal" camera parameter).
>    2. Focal distance (distance to point of perfect focus).
>    3. f-stop (traditional photographic measure of the aperture size).
> These parameters truly "belong" to the camera, rather than to the 
> scene or exporter settings.  This is because it makes sense for 
> different cameras to have different settings, and for the settings to 
> be animated with the camera itself.

Interesting! Am I right to assume that these parameters are 
Aqsis-specific? As in, they have no utility when rendering from within 
Blender, and would only be shown when Aqsis is selected as a renderer?

> In the Aqsis CVS version of Tuhopuu, these camera parameters are 
> completely finished, hooked up to IPOs, etc.  Here's a screenshot 
> showing them in action:
>    http://www.warpax.com/temp/screenshot-new-camera.png
>
> Given that it's all set up for people to play with, I have a few 
> questions.  These are probably best answered by those who are the true 
> "custodians" of Blender (probably most of whom are active on this 
> list):
>    1. Are there any changes I should make?
>    2. I'd like to display focal distance (the distance to the point of 
> perfect focus) in the scene.  Currently, I do this with a simple cross 
> along a line from the camera, which is displayed when "ShowLimits" is 
> selected.  Should this display be improved?  Should it perhaps include 
> some indication of the depth of field: ie, some kind of "in focus 
> range", over which the focal blur is always within some arbitrary 
> value?  Any ideas (or mockups) for how this should look?

The first thing that personally comes to mind for showing the in-focus 
area is using 3 circles, as a kind of metaphor for the circles of 
confusion in the DOF effect - 
http://mke3.net:9000/blender/ui/controls/camera_circ_conf.png

Definition of circles of confusion for non-photography types: 
http://www.tpub.com/content/photography/14209/css/14209_38.htm

> PS -
> Q: Why do we need "FocalLen" when "Lens" apparently contains the same 
> information?
> A: Lens in Blender controls the angular field-of-view of the camera, 
> whereas FocalLen is the camera focal length expressed in Blender scene 
> units.  The alternative to this scheme would be to use the Lens 
> setting in combination with a less-intuitive scale factor to find the 
> focal length in scene units.  I thought it was best to separate these 
> two so that the settings were available in the most straightforward 
> fashion.

Would the 'FocalLen' operate independently of Blender's 'Lens', or 
would changing the 'FocalLen' actually change the zoom when looking 
through the camera? If so, this seems a little confusing to me, having 
two controls that change the same property, but with different scaling.

Cheers

Matt

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