For Blender: 2.32 - Version française disponible(fr)

::Preliminaries::

As well as anything related to raytracing with Blender, because of the supplementary calculus time required by your computer, raytracing is only an option that you should feel free to activate and deactivate. This is done by the mean of the Scene menu (F10 key). The Render tab shows a button labeled Ray you will have to activate in order to use raytracing in your pictures.

ray

::Basic settings::

Let's start by downloading our working scene (please check attached files). After unpacking and opening the file, select the only lamp, go to the Shading (F5) menu, and then in the Lamp buttons.

regular-lamp

In the Preview tab, with your lamp selected, activate the Area button. The Lamp tab is automatically updated in order to show news slightly different options: choose a Square shape and increase the size of the edge of the square up to 2 (Size 2.00). In the Shadow and Spot tab, activate the Ray shadow button, and note that new options appear: increase the number of Samples up to 8 (less if you only have an old computer).

lamp-buttons

You will immediately suffer from the first issue concerning the Area lamps: with the very same Energy and Dist values, a lamp Area and a regular Lamp don't have the same lighting potential. Of course, you can lower the Energy of the lamp to correct this, but a better way is to lower the Dist value, because the lighting of Area lamps is known to be more sensitive to the distance. A value of 10.00 is generally a good start.

area-toomuch-Dist
Dist = 30.00
good-dist
Dist = 10.00

::Fine tuning of the lamp::

The first tests with this kind of lamp already give satisfactory results, but you can achieve more realist lighting with more adjustement of the lamp's parameters. In particular, you can define more precisely its shape and its dimensions so that it is the closer to the kind of light source to be simulated. For example, in order to simulate the lighting coming through a window, you would change the shape of the lamp to Rect, and set accordingly its dimensions.

Rect-options

You will note that in the 3D views, you can not only move the lamp using the G key, as for every other lamp, but also rotate it using the R key, so that you can translate and orient the lamp and make the lighting more realist.

  • Shape:

You can set an appropriate shape to your area light: either Square, either Rectangular. Try as much as you can to stick to the shapes and dimensions of the "real" entites producing the lighting in order to get more believable results.

  • Size:

The Square shape comes with a unique Size setting button, while the Rect shape come with two settings buttons, Size X and Size Y. These buttons give you control over the dimensions of your area light.

::Dealing with the shadows::

We already saw in the basic settings that you only need to increase the Samples value in order to soften the borders of the shadows. Everything else is a matter of finding a compromise between visal impact and supplementary time spent into calculus of the picture. Of course, the more you increase Samples, the longer it will take to render the picture.

  • Umbra:

This button let you emphasize the intensity of shadows in the area fully protected by the direct rays shot by the lighting source. Used with softened shadows, the lighting conditions between fully shadowed areas and fully lit areas change more quickly.

without-umbra
with-umbra
Without and then with Umbra

  • Dither:

This is a sampling applied over the borders of the shadows, quite the same way anti-aliasing is applied by the OSA button on the borders of an object. Il helps to soften a little more the borders of shadows when the Samples is set low. It is not useful with high Samples values. The following test is made with Samples 2.00.

no-dither
dither
Without and then with Dither

  • Noise:

Les échantillons d'ombres sont décalés les uns par rapport aux autres de façon pseudo aléatoire, ce qui a pour effet d'adoucir

The shadow samples are offsted from each other in a pseudo-random way, which artificially soften the borders of the shadows. Once again, this option is not very useful when you use a high Samples value, the drawback is that this button generates a quite visible grainyness.

no-noise
noise
Without and then with Noise

To sum up things, if your computer has a low computing power and if you want to use Area lamps and raytracing anyway, you could find useful to set a low Samples value (like 2.00) and activate the buttons Dither and/or Noise in order to simulate slightly softer shadows. It stays obvious that these results will never be better than the same lighting with high Samples values.

::Resize your scene::

You will note that changing the Size parameter of your Area lamp doesn't effect the lightinh intensity of your scene. On the other hand, rescaling the lamp using the S key could dramatically increase or decrease the lighting intensity of the scene. This behavior has been coded this way so that you can fine tune all your light setting and then decide to scale up (or down) the whole scene without suffering from a drastic change in the lighting intesity. If you only want to change the dimensions of your Area lamp, without messing with its lighting intensity, you are strongly invited to use the Size buttons instead.

final