Soft shadows and Area lights
Blender is able to produce soft shadows from any of its main lamps, quite easily. But we would still have to deal with the main usage for area lights (in order to answer to a very frequently asked question by many beginners), that is achieving shadows with soft borders, useful for simulating the lighting of a supermarket, a computer screen or a cloudy outdoor.
This article shows the usage of soft shadows, and then of the Area ligths whose settings are sometimes difficult to master.
For Blender: 2.50 Alpha 2 or better
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 Render menu. The Shading panel shows two options labeled Ray Tracing and Shadows you will have to activate in order to use raytraced shadows in your pictures.
Good to Know:
The following options are found in the Shadow panel of the Object Data menu, when any lamp is selected.
This button enables shadows computed according to the raytracing methods: the shadows are exact and the borders are perfectly sharp (contrary to the the shadows that are obtained to the shadow buffers scanline method, that are more approximate, with varying quality, but easily turned into soft shadows).
Color of Shadows cast
This color picker lets you choose the color of the shadows cat by the lamp. The purpose of colored shadows is to simulate ambient light more quickly than using radiosity or ambient occlusion.
2. Soft shadows
When you add a new lamp in a scene, the Shadow panel reveals interesting features for the realism of your lighting. The soft shadows are obtained through the use of the following parameters. They actually fake the lighting so that even point light sources spread their luminosity as if they were surfaces.
2.1 Adaptive QMC and Constant QMC
There we specify sampling mode of soft shadows. The Constant mode is more realist, but requires a greater number of Samples in order to get a better visual result (less noise and grain). Adaptive enables sampling variation, so that the sampling is increased where it is the most useful. Works well with a low Samples value, but provides poorer visual result (more noise and grain).
The choice between the two modes results from a compromise between visual aspect and render time.
2.2 Soft Size
This parameter sets the virtual size of the area lamp that is to generate fost shadows. The more the size is close to zero, the more it tends toward a point light with sharp shadows. On the other hand, the more the size is high, the more the shadows become diffuse. This parameter is only useful with Samples greater than
The more diffuse the shadows, the more you have to increase the sampling to get an attractive result. Be careful with high Samples values, because of the render times!
3. Area lights
The area lights are an older way to produce soft shadows, and offer more complete settings. Because of this, we will pay to them a special attention.
3.1 Basic settings
Let's start by downloading our testing scene attached to this article. Open the file, and with the only lamp selected, go to the Object Data menu, and then in the Lamp buttons.
In the Lamp panel, activate the Area option. The others panel are automatically updated to show new different options: in the Area Shape panel, choose the Square option and increase the size of the edge of the square up to
3.000). In the Shadow panel, make sure that the Ray Shadow option is active, and note that slightly different sampling options are available: increase the number of Samples up to
8 (less if you only have an old computer).
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.
Tip: The Gamma value from the Lamp panel, in the Object Data menu of the Area lamp can also help to adjust the exposure of the image.
3.2 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.
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.
You can set an appropriate shape to your area light: either Square, either Rectangler, using the proper option buttons. 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.
The Square shape comes with a unique Size setting button, while the Rectangle shape comes with two settings buttons, Size X and Size Y. These buttons give you control over the proportions of your area light.
Hint: Resize your scene
You will note that changing the Size parameter of your Area lamp doesn't effect the lighting intensity of your scene. On the other hand, rescaling the lamp using the
Skey 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 intensity. 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.
3.3 Dealing with the shadows
You are know fairly knowledgeable with the Adaptive QMC and Constant QMC methods for soft shadows. But the Constant Jittered method introduces a few more parameters you might like to explore.
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.
This is a sampling applied over the borders of the shadows, quite the same way anti-aliasing is applied on the borders of an object. It 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
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.
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.
Article written on January the 2nd, 2005.
Updated on November the 30th, 2008 for Blender 2.48a. Comments re-initialized.
Updated on June the 21st, 2010 for Blender 2.50 Alpha 2.