VRay for SketchUp Manual
The Characteristics of Rectangular Light
Rectangular Light plays a very important role in V-Ray. Despite its ease of use,
it also gets a smoother final result. Unlike the Point 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 characteristics about
Size does matter
See images below and you will find the size of the Rectangular Light has an
affect 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 one on the top 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 Point
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 one on the top
has the Invisible option unchecked so the light appeared in the image. When
apply a reflective material to the object, the light will also be reflected on
the object. The image on the bottom 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 SketchUp face orientation of
the Rectangular Light. Reverse the face and you can change the direction of the
The Double Sided option can turn the light direction from one side to both
sides 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.
The Double Sided option is usually used when the render is 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
the 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
3. Double sided option checked
|Pay attention to the size, location and
intensity factors of Rectangular Light because they will affect the
brightness and shadow clarity of your final result.
If the light is placed to far away and the subject is not bright
enough, you can either increase the intensity or size of the light. On
the other hand, you can lower the intensity or reduce the size of the
light if you place the light too close or too bright. You will need to
keep adjusting the size, location and the intensity of the rectangular
light in order to get good lighting result.
Intensity light unit allow you to select different physical units of the light.
Using the correct intensity unit will help you to get the correct result when
you are using the Physical Camera.
This takes into consideration the units scale of the scene.
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 is 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 depends on its size.
Watts - the light power calculated in watts. The light's intensity does not
depend on it's 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 depends on its size.