Le 2023-01-24 à 16:17, 88Keys a écrit :
> Hello.
> 
> I'm trying to work with Area Lights, but I can't seem to orient them correctly.
> I've been trying a <-50 , 0 , 50 > , <50 , 0 , 50 > and that doesn't seem to
> illuminate my scene, so I tried a <-50 , 0 , 0 > , < 0 , 50 , 0 > in an attempt
> to make the angles at 90 degrees to each other, but that doesn't seem to have
> worked either.
> 
> Any tips on how to generate a proper Area Light?  The documentation is a little
> slim.  What I have developed seems pretty dull, too.
> 
> Thanks very much.
> 
Always start with with your light set as a regular light.

Once the light is properly placed, add the area_light options.
It's better to have the sides at 90° from one another, but, that's not a 
requirement. It'll only make your area_light into a parallelogram.

If you want an area_light that act like a bright ball or light bulb, you 
are better using the circular and orient options.
The circular option make the light into a circle, or ellipse if the 
sides are of different length.
With orient active, the orientation of the array is no longer important. 
It demand that the light starts as a square with the same sampling 
density in both direction. If not, a warning is displayed and the 
offending part altered to meet the requirement.

Remember that the vectors used to define the area_light are ALWAYS 
relative to the location of the area_light, NEVER the origin of the scene.

Sample :

light_source{
	<100, 1000, 75>// the location
	rgb 1 // colour and intensity, can be more than 1
//add the following only after the light is properly placed
	area_light 20*x 20*y// It's dimension or extant
	33 33// maximum number of samples to use
	adaptive 0// turn on adaptive sampling starting
// with the corners, or a 2x2 array
//increase the value if you get artefacts
	circular // make it into a circle
	orient // always oriented toward the location currently evaluated
   }

The starting sampling arrays associated with various adaptive values :
Adaptive	MINIMUM		suggested minimum array
Value		sampling	size to use to see
		to use		the benefit
0		2 x 2		9 x 9
1		3 x 3		33 x 33
2		5 x 5		65 x 65
3		9 x 9		129 x 129
4		17 x 17		257 x 257
5		33 x 33		513 x 513

Any sampling array size between those values will be silently increased 
to the following size of the list. A 4 x 4 adaptive is really 5 x 5, 6 x 
6 is promoted to 9 x 9 and 10 x 10 become 17 x 17.

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