From BlenderWiki
Area
Mode: All modes
Panel: Lamp (Shading context, Lamp sub-context, F5)
Description
The Area lamp simulates light originating from a surface (or surface-like) emitter, for example, a TV screen, your supermarket’s neons, a window or a cloudy sky are just a few types. The area lamp produces shadows with soft borders by sampling a lamp along a grid the size of which is defined by the user. This is in direct contrast to point-like artificial lights which produce sharp borders.
Options
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| Area light’s Lamp panel. |
- Common options
- The Dist, Energy and Color settings are common to most types of lamps, and are described here.
- Note that the Dist setting is much more sensitive and important for Area lamps than for others, usually any objects within the range of Dist will be blown out and overexposed. For best results, set the Dist to just below the distance to the object that you want to illuminate.
- The Layer, Negative, No Diffuse and No Specular settings control what the lamp affect, as described in this page.
- Gamma
- Amount to gamma correct the brightness of illumination. Higher values give more contrast and shorter falloff.
The Area lamp doesn’t have light falloff settings. It uses an “inverse quadratic” attenuation law (TODO: is this true?). The only way to control its falloff is to use the Dist and/or Gamma settings.
It replaces the light attenuation controls (falloff type and Sphere button) with Shape and Size controls. The first one lets you choose the shape of the area and the second the size of the shape (in Blender Units).
- Square
- Emit light from a square area.
- Size
- The length of the square’s edge.
- Rect
- Emit light from a rectangular area.
- SizeX
- The rectangle’s horizontal width.
- SizeY
- The rectangle’s vertical height.
Shape Tips
Choosing the appropriate shape for your Area light will enhance the believability of your scene. For example, you may have an indoor scene and would like to simulate light entering through a window. You could place a Rect area lamp in a window (vertical) or from neons (horizontal) with proper ratios for SizeX and SizeY. For the simulation of the light emitted by a TV-screen a vertical Square area lamp would be better in most cases.
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“Shadow and Spot” Panel
When an Area light source is selected, the Shadow and Spot panel has the following default layout:
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| The Shadow and Spot panel when Area light source is selected. | ||
As its only purpose for this lamp is about raytraced shadows, it is described in details here.
Examples
In (Render example), only one sphere is visible in order to emphasize the shadows created by the Area light, with Constant Jittered sample generator. Here the Samples has been set to 3 which will generate 3 × 3 = 9 shadows. In addition, the Size of the square has been made relatively large (30) in order to exaggerate the shadows displaced from one another; the numbers are marked in an arbitrary order. Think of the Size as pushing the lights away from each other in the plane of the square.
In the second example below, using the Constant Jittered sample generator, the first image on the left shows a Samples setting of 2 which generates four lights and hence four shadows. You can clearly see the shadows, but if you stand back far enough from the image it will appear as a single “soft” shadow. This can be improved by enabling Dithering and improved further by enabling Noise.
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You can find more useful and complete examples about lamps in the “lighting rigs” page.
Technical Details
The (Principles behind the Area light) picture helps to understand how the soft shadows are simulated.
(a) is the Area light as defined in Blender. If its shape is Square, then the softness of the shadow is defined by the number of light Samples in each direction of the shape. For example, (b) illustrates the equivalent case of an Area light (Square shape), with Samples set at 3 on the Shadow and Spot panel.
The Area lamp is then considered as a grid with a resolution of three in each direction, and with a light dupliverted at each node for a total of nine lights.
In case (a), the energy (E) is E/1, and in case (b), the energy of each individual pseudo-light is equal to E/(Nbr of lights). Each pseudo-light produces a faint shadow (proportional to its energy), and the overlay of the shadows produces the soft shadow (it is darker where the individual shadows overlap, and lighter everywhere else).
Hints
You will note that changing the Size parameter of your area lamp doesn’t affect the lighting intensity of your scene. On the other hand, rescaling the lamp using the S in the 3D View 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 settings and then decide to scale up (or down) the whole scene without suffering from a drastic change in the lighting intensity. If you only want to change the dimensions of your Area lamp, without messing with its lighting intensity, you are strongly encouraged to use the Size button(s) instead.
With equal Energy and Dist values, an area lamp and a regular lamp will not light the scene with the same intensity. The area lamp will have a tendency to “blow out” the highlights, but this can be corrected using the Exp slider in the World sub-context.
If your computer isn’t very fast, when using the Constant Jittered sample generator method, you could find it useful to set a low Samples value (like 2) and activate Dither and/or Noise in order to simulate slightly softer shadows. However, these results will never be better than the same lighting with high Samples values.
See Also
