VRay for Rhino Manual

Rectangular Light plays a very important role in V-Ray. Despite its ease of use, it also gets a smoother final result. Unlike the Spot Light, Rectangular Light doesn't have the worry about the angle of the light. It also allows reflective material to bounce the light around the scene. Other type of lights will not be seen in a reflective object. Below are some important characters about Rectangular Light.

Size does matter

See images below and you will find the size of the Rectangular Light has an affect on its intensity.

Shadow changes according to the size

Larger Rectangular Light spreads out to a larger area, so the shadow is not as clear as you will get from a smaller Rectangular Light.

Compare images below and you will see the differences between two different light sizes. The first image below is rendered with a smaller light.

If you want to have a stronger shadow, we do not recommend you set the intensity way high and make the light size really small. It's better to use a different light type in V-Ray. Please see dialogue box of how to create a Parallel Light later.

Impacts on reflective objects due to Visible and Invisible Rectangular Light

There is an Invisible option in Rectangular Light. It allows the light visible or invisible from the render image. See images below. The first image below has the Invisible option unchecked so the light appeared in the image. When apply a reflective material to the object, the light will also being reflected on the object. The second image below has the Invisible option checked. Thus, you don't see the light in the image or on the object with reflective material applied to it.

The default setting for Rectangular Light has the Invisible option unchecked. If you see any unusual dark shadow in your rendered image, please check if your camera is blocked by the Rectangular Light in the scene.

Double Sided Option

You can tell the direction of the light from the short line on one side of the Rectangular Light. Rotate the light and you can change the direction of the light.

The Double Sided option can turn the light direction from one side to both side of the light. Just like to create two lights with opposite directions. Move the light away from the floor or wall to avoid any black out area.

Double Sided option usually used when renders a big interior scene. It helps to light up the space without using too many lights. Normally we don't use it when render a product scene. There will be more discussion about lighting and environment lighting later on.

The default has the Double Sided option unchecked. Of course, if you check and Invisible option, you will not see the light in the three images below.

1. Light direction towards the left side.

2. Light direction towards the right side.

3. Double sided option checked.

Light Units

Intensity light unit allow you select different physical unit of the light. Using the correct intensity unit will help you to get the correct result when you are using the Physical Camera. This take in consideration the units scale of the scene.

Values:

Scalar - means the final color of the light it is given by the color and multiplier of the light without any conversion.

Lumens - the total power of the visible light was measured in lumens. The light's intensity does not depend on its size.

lm/m/m/sr - the light power calculated in lumens per square meter per steradias. The light's intensity depend on its size.

Watts - the light power calculated in watts. The light's intensity does not depend on its size. Does not work like a real light bulb. (Ex. real 100W light bulb emits between 2 and 3 watts as visible light.

w/m/m/sr - the total visible light power calculated in watts per square meter per steradian. The light's intensity depend on its size.