Rendering Tutorial - VRay v3.2

Using the renderer VRay, it is possible to render a scene with only a High Dynamic Range image as the lightsource:



Using just HDR images, such as CGSkies skydomes, it is possible to light an entire 3d scene without any additional light source, the amount of work needed to set it up is minimal.

(Note: In our experience only VRay manages to render sharp shadows when using a HDR image as the only lightsource. Other render engines may need additional support lights to achieve sharp shadows.)

For purpose of this tutorial we'll be using a simple startup scene consisting of:

- sphere mesh with reflective material applied (VRayMtl)
- several rectangle and sphere meshes with various materials applied, to show the lighting better (VRayMtl)
- VrayPhysicalCam
- 2 VrayLight (dome) entities

In this tutorial we will show all settings needed to create the lighing setup. You can also download our sample scene for 3D Studio Max 2012 and V-Ray Advanced 3.20.03

Our scene looks like this:



The following V-Ray renderer settings need to be set:



In this example render we use the CGSkies.com skydome number 0228 HDR image. You can download a small resolution sample for free (1500x750px) or purchase the full resolution version (15000x7500px). For lighting purposes the free sample has enough resolution.

To setup the HDR image lighting we need to setup two VrayLight entities, one to control lighting and a second to control the skydome image.
The reason we setup two VrayLight entities is so we can alter the light behaviour without worrying about changes to the background image or reflections and vice versa.

We name these 'LightReflection' and 'LightIllumination'. In order to work as we expected, some settings need to be changed for both light entites as follows:



Now we need to modify the materials for the lighting. Two maps were created when we selected VrayHDR as the texture for the light entities, to bring them to the main slate material view, we have to double click on their names in the scene materials list.

We'll use 'Spherical' mapping type for our HDR maps, this mapping type enables the use of 'horizontal rotation' setting that helps to position the skydome in an easy way. (3dsmax standard mapping allows to shift the sky vertically as well but is more complex in use & setup)

Also, for this particular sky multiply setting of 20 and gamma of 0,65 for light, 25 and 0,8 for dome should make a good starting point. But experiment!
Illustration:



Now to tweak the lighting and background/backdrop's appearance we can use 'Multiply' and 'Gamma' values in the HDR map settings. See them as 'Brightness' and 'Contrast' settings for your HDR image. Note: Color space type: Inverse gamma needs to be selected first.

In essence, smaller 'Gamma' value (generally all within range of 0.5-1.0) will result in more contrast between the light and shadows. Altering gamma might also affect brightness of the light source. As demonstrated here (notice how the reflected skydome remains the same as it is separate from the light source):



Multiply value will alter the general brightness of the HDR image (resulting in more ambient light coming from the skybox).
Play with the values for the best effect!

Download our test scene here: download our sample scene

Instructions for Vray 2.1