VRay for SketchUp Manual
Lighting plays a key
role in the rendering process. You simply can 't get a good rendering result
without a good lighting environment.
Same as real space lighting, light sources are divided into direct and
indirect lighting. Direct lighting is using the light command to create
Rectangular Light and Omni Light to use directly on the object. Indirect
lighting refers to any lighting which is from bouncing light, or an environment.
Lets do a test
Open file: Chairs-Illumination-01.skp,
there is no light in the scene. Light source is from Environment light.
1. So far the chairs and ground are using
the same Val230 off white color. Render it with GI default setting to 1 and get
the result as image shown below.
2. Increase the GI value to 2 without
changing the color, the result is shown below.
3. Do not change the GI value and change
the Brightness to Val 55 under the Texture Editor. Render it again and the
result is very close to the first image on the top.
The reason for doing this test is to let users understand the importance
between lighting and material. Should the lighting be adjusted to accommodate
material or should material be adjusted to accommodate lighting?
It is clear from the previous example that the lighting must be adjusted to
accommodate materials. With the second image from the previous test if we
created another material and inserted into the scene, it would not render how we
Here’s another example. Lets take the shirt that you’re wearing right now.
What color is it? If you walked into a closet with no light, what would the
color of your shirt be? The answer is that the color of your shirt would be the
same, BUT it would appear different based on the lighting environment. This is
why you should adjust your lighting to achieve the desired affect, as opposed to
changing the materials.
With an incorrect lighting environment, such as the second part of the
example on the previous page, it will be very hard to predict how your scene
will react. When adding an new material, it will not look how it did when you
created it, thus making it harder to achieve the original intended appearance
for the material. Incorrect lighting also has an adverse affect on other aspects
of your rendering and may affect shadows, reflections, and even make your
rendering take longer than it should. Now you see why having a proper lighting
solution is very important.
Interior or Exterior?
When facing the task of illumination, separate it into interior illumination
and exterior illumination. Here, exterior means open space. For example, place an
object on the ground without any wall around it to block the light. It's easier
to adjust illumination for open space. Interior means light source is blocked by
wall or other similar objects in the scene; an enclosed space in which the
environment light will not have a direct effect to the object. Or maybe some
openings on the wall or windows allow part of environment light to come through
them. Interior lighting is generally more complex than exterior lighting.
Image on the left shows open space illumination and image on the right shows
the semi-open space illumination.
Image on the left shows the same semi-open space but add one more opening to
the wall. The brightness increased due to second opening added to the wall.
Image on the right shows different locations for openings also affect the
brightness of the scene.
Techniques for adjusting illumination
Before rendering a scene, try to finish all the modeling as this greatly
simplifies the task of adjusting the illumination. The number of objects, object
location, material type, color and even size will all affect the illumination in
When beginning to create the lighting solution it is important to have a
solid base in which to begin evaluating how you will need to light your scene,
as well as how it will react to lighting. With VRay this task is very easy
because of how the environment light works. Basically, with your environment
color set to white (255,255,255) and the intensity set to 1, you should get a
neutral lighting of your scene. This is useful in that it will allow you to
properly assess the appearance of your materials, as well see if there are any
areas of your scene which will naturally receive more or less light from the
Now lets see this in action. Open file
Chairs-Illumination-02.skp. This is an easy open space example, there
is no light added to the scene, and the Environment color and intensity are
currently set to Val 255 and 1 respectively.
Using a white floor color is important as it will show the most amount of
light that will effect the scene. This is because white allows the most amount
of light energy to be retained after it bounces off a surface. With the white
floor, we know that if we change its material to something that is darker, than
we can expect a little less bounced light in our scene. In an exterior scene
like this one the effect is minimal, but when creating an interior illumination
solution this is an important thing to know.
1. Assign the Val 230 color to floor,
R244 G40 B11 red color to chairs first, render it and the result is as shown
2. Re-assign the R255 G150 B135 red color
to the chair and render; you will get the results as below.
From the two images above we can see the colors for the floor and chair are
rendered very close to actual colors, which means the Environment lighting is
set to correct intensity and brightness for creating good illumination.
Otherwise, if the intensity is too strong, it will make the floor and chair
appear brighter that the values that we set when we made the material.
Now that we have a good render we can begin the task of adding more lighting
into the scene. Depending on what you are trying to create this may only
required one additional light (the sun perhaps) or many lights. The important
thing to remember is that the lighting must be balanced. Since we already have a
scene which would become overly bright, or burned as it is sometimes called, if
any additional light is added there must be a compromise between the different
lights. In most cases this will mean that the environment intensity will be
decreased, but the ratio between environment lights and other lights is
something that you must determine. Try out different options; one where the
environment light is stronger than other lights, and another where other lights
are stronger than the environment.
Instead of using a color for an Environment light source, V-Ray also supports
HDR images to use as Environment light source. Open file
1. Open V-Ray for SketchUp’s Render
Options, open Environment menu and click on the "m" at the right of GI to enter
2. Choose Bitmap from Type, click on "m"
beside File and import an .hdr file.
3. Because the textures is being applied
to the environment and not an object make sure you check the Environment under
UVW after the file is imported.
Render it and you will get the image on the bottom. You will see a big difference
between this image and the image that used only color for Environment light
source. This is because the HDR is providing the illumination for the scene
based on the colors and intensities of the image.
4. If you want the object reflect the HDR
image Environment as well, you can assign the same HDR image to the Environment
Background, and make sure the UVW is set to Environment. After the Background
HDR is added, the result is as image on the bottom.
To compare, below are three images rendered with different HDR images as the
Environment light sources. You can see the light and color change dramatically
according to each HDR image.
|Due to the fact that HDR images are usually
provided by others, the lighting environment may not produce the desired
effect. It may take some time to adjust the intensity.
Although HDR image produces better results than a normal image, HDRs
still lack the true brightness of a natural environment. So normally
it's used only for Environment light source, and usually some additional
light is added.
Environment light source
If the user does not have an HDR image, a regular Bitmap can be also used as
Environment light source. Although a normal Bitmap does not have the same ability
to create as dynamic an environment, normal images are very easy to get. As long
as you pick the right Bitmap and control the Intensity well, it can still be a
very good Environment light source.
The three images below are rendered with a different Bitmap. If you
compare them to image rendered with HDR images, it is not as easy to determine
the direction of the light and the shadows are not very clear.
Environment light source
for semi-open space
We used open space to discuss Environment light source for our last example . Now
it is time to use semi-open interior space for this example to see differences
between interior and exterior illumination.
Open file: GI Environment-01.3dm. In the
scene is an enclosed cube with an open on the top. There are some objects placed
on the wall next to the opening wall and there is no light in the box. All
objects used Val190 gray color, current GI Intensity is 2, color is light blue.
Render it and you will get the almost black image on the bottom. The result is
due to no light in the scene and only a small opening allows the Environment
light to come in.
Increase the GI Intensity to 4 and render it again. The result is as below, a
little bit brighter this time.
Increase the GI to 8 and render again. The result is closer to reasonable
This example shows that Environment light in semi-open spaces usually doesn’t
lead to a proper solution the first time.
When beginning to set up the illumination for interior space, a first step
should be to check how many openings in the scene allow environment light to
come in. This includes transparent objects like windows or doors. It is also
important to know how many lights are intended to be in the final scene, as well
as what time of day the rendering is meant to depict. These are all very helpful
for setting the Environment light correctly.
Even if the Environment lighting is set to the desired level for the final
scene, you will still wind up having to adjust it based on the materials and
other lights that will be added to the scene. Very often the camera got moved
during this process and the quality and brightness are not what you were
expecting. Even though the interior lighting is under control, once the camera
is pulled out from the box, you will get the bright white rendered result as the
It will still be necessary to add light in the room, adjust the brightness
and render as image on the bottom.