V-Ray uses photometric light.
Lights can be placed in the scene by clicking the right mouse button wherever in the layout window, and selecting the command New light. In this way you can choose among 3 different types of light: bulb, spot, neon. Moreover, there are objects in the components library that already integrate a light inside them.
The typology name to search for is Furniture – Spot lighting, in Maticad manufacturer.
They are not available in the standard installation DVD, but you can download them inside the Live! page, even if you have not processed the (optional) download service. They are modern and classic lights containing photometric spots and neon. With such objects you just need to drag and drop them in the scene, without taking care of the light setup.
Let’s try working with lights: open/create a project, place a light and open its properties section (double click the light over the image or one of the lines, or click the right mouse button and choose the command Properties).
Advanced button allows you to open a detailed section, where to find all parameters involved in the rendering process. Let’s have a look at them.
Photometric light: this light simulates the behaviour of real lights, also affected by or affecting other objects/effects. Photometric lights are based on some basic parameters: luminous flux, luminance and light intensity. This set of variables allows you to place more detailed and real lights, for a better result and rendered image. You can use one of the Preset values in order to change light intensity; they are real light available on the market, and their power is expressed in Watts. Note that different lights will generate different illumination effects, even with the same Watt power, Candela (cd) or Lumen (lm). The preview image will help you better understanding what’s the selected light behaviour and shape.
Physical light: this type of light can be used only with mental ray®.
In physical lights you can use preset as seen in the paragraph above, but also IES light: IES lights are prepared and shared by the manufacturer with the real features of the light. Manufacturer makes available a file with .ies extension, where the rendering engine can find all details for the rendering process. If the standard lights irradiate merely wherever in the space (360°), IES lights can provide the engine detailed information about the direction, intensity and decay in all directions. For this reason, using the correct IES allows you to avoid any problem related to wrong light effects. As an example, the next images let you see the same scene rendered with different IES lights. If you look at the shape of the light in the technical diagram, you can see the result in the rendered image (also note that this is a closed room, hence no sun or sky light is entering the room).
You can download new IES files from the manufacturers’ web site: save them in the …\DomuS3D2010\Lights folder in order to see them in the Advanced mask of the light; in the next sections we’ll have a look at the controls available in this mask.
Multiplier (1 - 1000): this value will be multiplied with the intensity of the light; for this reason, we suggest you to change the intensity of the light, rather than the multiplier.
% spot penumbra: this parameter is available just for spot lights. It gives you the option of customizing the amplitude of the shading area. The percentage value is referred to the angle defined by the spot.
If you want objects illuminated by this light to create a soft shadow effect, light does not have to be punctual, but has to be represented by an area (area lights). For this reason No effect is related to a punctual light, while rectangular, circular, spherical or cylindrical refer to area lights and will create soft shadows.
The behaviour of area lights can be easily understood by looking the next images: the left one represents a punctual light, the right one an area light.
A punctual light generates defined shadows only without any penumbra
An area light generates a shadow with a customizable penumbra
If you decide to use IES files, Multiplier and % spot penumbra are automatically disabled. If you want to increase or decrease the IES light intensity you need to enable the check named Custom intensity and change the intensity value by typing the needed Lumen or Candela.
Soft Shadows (area lights): if No effect is enabled, light is punctual and creates just delimited shadows. If you enable a different option, light becomes larger and starts creating soft shadows. If Visible is checked you will see the light in the rendered scene; if it is not, you will see just the light effects. If the light you’re dealing with is a bulb, we suggest you to choose the spherical shape: by changing Radius and Soft Shadow Quality you can reach the needed result. Default value for Soft Shadow Quality is 8: if you increase this value (e.g. 16 or 32) the quality of the shadow will be better, even if the engine will take more time in order to complete the process.
Punctual light - Delimited shadow
Area light - Soft shadow
If the light is a Spot Light, the area can be rectangular or circular (see next images). With the former, you will specify the height and width, with the latter you will specify the radius. In this case too, you will physically see the light In the rendered image if Visible is checked.
Placing a neon in the scene means specifying 2 delimitation points as it is a linear light: those points define the orientation and the length of the neon in space. Neon has to be configured as physical, visible light, with a cylindrical shape, where you can decide intensity and radius of the cylinder.
In case of IES lights, information about the light, including the way to generate soft shadows, are included in the .ies file; you can, indeed, adjust quality as the related parameter still remains enabled.
It is important to try out the lights and light effects you have seen in this chapter, as lights and illumination are of paramount importance while setting up a stunning rendered image; for example and as an exercise, you can use a very simple project (in order to reduce rendering time) and one light at a time in order to try out the effect that light gives to the scene.
This article is valid for DomuS3D® 2017 and later versions