Example 1: Single-sided vs Double-sided lights

This example demonstrates the difference between a single-sided and a double-sided 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. Larger luminaires have larger surfaces.

Radius = 3
Radius = 6
Radius = 12

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 C4D 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: Sky light, self-illuminated panels and V-Ray Lights

Here is an example of a simple room where the light comes from the environment. The scene was rendered in several different ways:

In all cases, the Light cache was used as a secondary GI engine. The environment, the self-illuminated panel, and the V-Ray Light all have the exact same color and Intensity.

Environment light (sky light) only
Self-illuminated panel at the window
V-Ray Light at the window
Environment light (sky light) only and brute force 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 V-Ray Light, 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 brute force GI instead of the irradiance map. This produces sharp shadows too, since the brute force GI is a non-blurry GI method. However, render time has increased quite a lot.

In this exampe, using a V-Ray Light 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 V-Ray renderer.

The LightDome light has been extended to support arbitrary texture maps that determine the amount of light coming from each direction on the virtual dome hemisphere. V-Ray 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.

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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.

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Position 2

The dome is rotated along its X axis to 90 degrees. Now the dome uses another part of the HDRI.

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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.

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Position 4

Another 90 degrees on the X axis from the previous position. A slightly sharper shadow has appeared.

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Position 5

Rotating the HDRI to -200 degree. Now the dome obviously uses some of the brightest range from it.

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This time we will reduce the HDRI Intensity and add more rotation.

Position 5

Rotating the HDRI to -300 degree. Notice how the Intensity affects the overal scene lighting. We haven’t change the dome position.

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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.

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Reset the horizontal rotation to 0.0. Multilpliers: 2.0 and 5.0

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Example 6: IBL and Caustics

From the Caustics, 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.

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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.

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Caustics Intensity set to 5.0 , 10.0 . Search distance 5.0 units.

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Other caustics examples.

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Example 7: Combined sampling of area lights

This example demonstrates combined sampling of area lights with direct and indirect lighting in V-Ray. A Mesh light is shown here, but the same principle applies in varying degrees to all other modes of the V-Ray Light. It is also valid for Luminosity Layer of V-Ray materials with the Direct illumination option on.

Direct illumination only (GI is off) – areas close to the light are noisy, while areas far from the light are smooth. It will take a lot more samples to clear the noise.Only GI (Brute force) – areas away from the light are noisy, while areas close to the light are smooth. It will take a lot more samples to clear the noise.Direct illumination and GI – combined sampling – both areas close to the light and areas away from it are smooth.