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Example 1: Single-sided vs Double-sided lights
This example demonstrates the difference between a single-sided and a
double-sided planar area light:
Double-sided is
off
Double-sided is
on
Example 2: Size of lights, shadows and intensity
The following images show how the size of a light affects shadows. Bigger
lights produce blurrier shadows, while smaller lights produce sharper
shadows:
U size = 3.0;
Normalize intensity is
on
U size = 6.0;
Normalize intensity is
on
U size = 12.0;
Normalize intensity is
on
In the above images, the light appears to be of constant intensity. This
is because the Normalize intensity option was
turned on. This is what the three images look
like with Normalize intensity
off (the default). Larger luminaires have larger
surfaces, which means that they emit more light. Note that the light
multiplier had to be adjusted compared to the previous three images in order
to produce similar light intensity; however, it is the same multiplier for
all three images.
U size = 3.0;
Normalize intensity is
off (default)
U size = 6.0;
Normalize intensity is
off (default)
U size = 12.0;
Normalize intensity is
off (default)
Example 3: Real-world lights have inverse square falloff
The following images demonstrate the No decay
parameter. In the real world the light sources attenuate with the inverse
square of the distance from the light to the shaded surface. However you can
disable light decay to achieve behavior similar to the standard 3dsmax
lights. The settings for the light source the same for both images with the
exception of the Decay parameter:
No decay is
off (default)
No decay is
on
Example 4: Skylight, self-illuminated panels and VRayLights
Here is an example of a simple room where the light comes from the
environment. The scene was rendered in several different ways:
- with just environment skylight with irradiance map as a primary engine;
- with a self-illuminated panel at the window, again with the irradiance
map as a primary engine;
- with a VRayLight at the window and the irradiance map as a primary GI
engine;
- with just environment skylight but with QMC GI as a primary engine.
In all cases, the Light cache was used as a secondary GI engine. The
environment, the self-illuminated panel, and the VRayLight all have the
exact same color and multiplier.
Environment light (skylight) only
Self-illuminated panel at the window
VRayLight at the window
Environment light (skylight) only and QMC GI
As you can see, all methods produce the same light distribution, but
there is a difference between render times and quality.
In the first two cases, we rely on the irradiance map to capture the
lighting coming from the window. The result is very similar, as well as the
rendering times. Since the irradiance map is a blurry method, the shadows
come out a little blurred. Although we can reduce the blurring by using
higher irradiance map settings, this will cost us additional render time.
In the third case, since we use a VRayLight, the shadows come out very
sharp and nice, and the rendering time is reduced. This is because the
irradiance map was calculated much faster - in the previous two cases, it
had to trace a lot of rays to sample the window accurately.
In the fourth case, we used QMC GI instead of the irradiance map. This
produces sharp shadows too, since the QMC GI is a non-blurry GI method.
However, render time has increased quite a lot.
In this exampe, using a VRayLight produces the best result in the
shortest time. However, if you need to have many lights, this method can
become quite slow, since every single light needs to be sampled.
Example 5: IBL (Image-Based Lighting)
IBL (image-based lighting) is a new feature, provided by VRay renderer.
The VRay dome light has been extended to support arbitrary texture maps
that determine the amount of light coming from each direction on the virtual
dome hemisphere. VRay then uses importance sampling to trace more rays in
the directions where most of the light is coming from. This ensures speed
and quality that were never before possible with pure gathering GI methods.
- Easy setup for image-based lighting (IBL);
- Importance sampling of the dome texture for fast and clean results;
- Support for photon mapping for fast and accurate caustic effects.
In the following example we will show how this works with a HDR image.
Initial position of the dome-light.
Z axis is perpendicular to the ground plane.
Rendered image
Position 1
This time the dome is rotated along its Z
axis to 90 degrees. Notice this has no effect, as the dome is using
the same part of the HDRI.
Rendered image
Position 2
The dome is rotated along its X axis to
90 degrees. Now the dome uses another part of the HDRI.
Rendered image
Position 3
The dome is rotated along its X axis to
-165 degrees. Notice how the shadows have changed, due to the softer
light in the HDRI.
Rendered image
Position 4
Another 90 degrees on the X axis from
the previous position. A slightly sharper shadow has appeared.
Rendered image
Now we are going to show how the HDRI parameters also can affect the
rendered image.
We will rotate the HDRI from the material editor.
Position 5
Rotating the HDRI to -200 degree.
Now the dome obviously uses some of the brightest range from it.
Rendered image
This time we will reduce the HDRI multiplier and add more rotation.
Position 5
Rotating the HDRI to -300 degree.
Notice how the multiplier affects the overal scene lighting. We
haven't change the dome position.
Rendered image
We will go further, adding some vertical rotation to the HDRI.
Position 5
Adding 50 degrees vertical rotation
to the HDRI. See how light and shadows have changed a lot. The
highlight position is different now.
Rendered image
Reset the horizontal rotation to 0.0.
Multilpliers: 2.0 and 5.0
Rendered image
Rendered image
Example 6: IBL and Caustics
From the VRay Caustics rollout, turn caustics on. Assign a glass material
on the cylinders.
Position 5
We are using the last setup of the HDRI from the Example 5.
The caustic effect is almost not visible.
Rendered image
We will raise the multilplier to 3.0 and set
the search distance to 1.0 unit.
Position 5
Now the effect is visible, though the search distance appear
to be too small.
Rendered image
Caustics multiplier set to 5.0 ,
10.0 . Search distance 5.0
units.
Rendered image
Rendered image
Other caustics examples.
Rendered image
Rendered image
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