Christian Froeschlin <chr### [at] chrfrde> wrote:
> Colin wrote:
>
> > So, say for example I put a point
> > light source above a flat surface. If I render it, I see that it's brightest
> > directly below the source. At a point some distance away from this centerline,
> > it is dimmer. What I would like is a metric for how much dimmer it is, as a
> > function of position. I assume this would be trivial from within the
> > ray-tracing algorithm; I'm just curious if it's possible from the user end.
>
> I think the only way from the user end is to go via the brightness.
>
> You can position an orthographic camera to look top down on the
> plane you are interested in. Using a homogenous texture and suitable
> light intensity should yield a reasonable intensity image.
>
> You need to make sure that the surface is lighted by photons only.
> This should be the case if the light source is completely blocked
> by some transparent object which is a photon target.
>
> You will wish to adapt the gamma settings to get a linear
> response curve, use 16-bit output for higher precision, and
> possibly try HDR output (this is in MegaPOV, there is also
> HDR support in 3.7b but I'm not sure its also for output?)
>
> This should already give you the relative intensities.
> Converting the pixel intensity to a physical unit may be
> tricky. For reference, you'd probably need some test lens
> which directs all photons onto the visible area.

I can work on referencing it easily using a known light source and photodiode
and calibrate accordingly (in the "real" world).

How do I read the brightness into a matrix of integer values corresponding to
the pixel locations?

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