Does CCD mean a photograph of an actual object?

Kari Kivisalo wrote:

> Here is the result of trying to visually match a Megapov 0.5 scene
> with a CCD image of the Cornell box. The only assumption made, based
> on observing the image on a calibrated monitor, was that the CCD image
> gamma is 2.2. This gamma was applied to the final image and extracted
> colors. Some red and green was subtracted from the extracted light
> surface color to remove the effects of color bleeding. Extracted red
> and green colors were only multiplied by a factor in linear space to
> match intensity. Area light color is RGB white. The POV-Ray scene
> geometry is reconstructed from the CCD image so it doesn't match
> exactly with the physical box. I think it's good enough for artistic
> purposes and considering that POV wasn't designed to produce realistic
> simulations :)
>
> The most difficult part was to get the darkening effect at the corner
> of the back wall and ceiling and it's not even that good. This also
> produced an anomaly at the small box/floor intersection. Notice also
> the good red color bleed on the tall box and not so good green color
> bleed on the small box/floor. The brightness of the lower front face
> of the tall box could be caused by different scene geometry or the
> incorrect light distribution from the area light (It's really a point
> light in all but the shadow calculations. This is why large area lights
> don't produce correct direct illumination. A patch to fix this would
> be nice :). Spotlight was used to simulate the cosine intensity falloff
> from planar light source.
>
> I'm not sure whether the settings I used are generally valid for all kinds
> of scenes or just this one. I will post the source with comments later
> so that the settings can be tested on different scenes and conditions.
>
> The most notable changes from the MP recommended values are:
>   brightness 2.5
>   gray_threshold 0.5
>
> First image: CCD image of the Cornell box.
>
> Second image: Rendering time about 0.5h but reduces significantly
>               without the (minor) corner effect. Requires more tweaking
>               to reduce rendering time.
>
> Third image: Megapov 0.5 high quality radiosity settings. 1.5min.
>
> Last: No radiosity. 20sec
>
> -----------------------------------------------------------------------
> Kari Kivisalo                                          www.kivisalo.net
>
>   ------------------------------------------------------------------------
>  [Image]

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