Mental Ray Lighting

In this beginner’s tutorial we’re going to illuminate a simple warehouse interior in 3ds Max. We’ll explore techniques to illuminate the interior through windows only. To keep things simple we’ll concentrate on lights that work with Final Gather and leave Global Illumination out of the discussion. I’m using 3ds Max 2011.

Step 1 Mental Ray Renderer

We’re going to render the scene with Mental Ray. By default 3ds Max uses the Scanline renderer so we have to change that. Change the renderer to Mental Ray ( Rendering > Render Setup… > Common tab > Assign Renderer > Production > mental ray Renderer ).

Step 2 Warehouse Geometry

This tutorial is about Mental Ray lighting but first we’ll create a really simple warehouse interior. Create a box ( Create panel > Geometry > Standard Primitives > Box ) in the top viewport . Modify the box ( Make a selection > Modify panel ) according to the following parameters:

• Length: 20
• Width: 20
• Height: 10
• Length Segs: 5
• Width Segs: 1
• Height Segs: 3

Step 3 Creating Windows

Next we’re going to create the windows. Add Edit Poly modifier to the box ( Make a selection > Modify panel > Modifier List > Object-Space Modifiers > Edit Poly ). Activate the polygon sub-object level, and delete two polygons in the right viewport.

Activate the vertex sub-object level and move the vertices to change the size and shape of the windows according to the picture below. ( Click and drag to select a row or column of vertices at once. )

Now the geometry is complete, but since we’re going to render the interior we should flip the normals of all the polygons:

1. Activate the polygon sub-object level
2. Select all polygons ( CTRL + a )
3. Go to the modify panel and click ‘Flip’ in the Edit Poly modifier ( Modify Panel > Edit Poly > Edit Polygons > Flip )
4. Deactivate the polygon sub-object level

Step 4 Creating Camera

Create a target camera ( Create panel > Cameras > Target ) in the top viewport and apply ( Make a selection > Modify panel ) the following parameters:

• Parameters
  • Lens: 20 ( wide angle lens is needed to get a good view of the interior )

Right-click on the Perspective view and press ‘c’ in the keyboard to change it to camera view. Move the camera inside the box to get a view like in the picture below.

Step 5 Warehouse Material

Open Material Editor ( Press ‘m’ in keyboard ) and create the material for the warehouse:

1. Click “Get Material” button and select ( doubleclick ) ‘Arch & Design (mi)’ from the list ( Materials > mental ray > Arch & Design ).
2. Select the warehouse and assign the material to it.
3. Reflectivity: 0 ( perfectly matte surface )

Apply diffuse and bump maps:

1. Bump map: Composite ( Maps > Standard > Composite )
2. Add Smoke map to the first layer of the Composite Map ( large scale details )

   Size: 0,5

   # Iterations: 20

   Color #1: Black

   Color #2:
   Dark Gray ( RGB 50, 50, 50 )

3. Add second layer to the Composite map. Change the blending mode to Addition. Add Speckle map to the second layer ( small scale details )

   Size: 0,4

   Color #1: Light gray ( RGB 180, 180, 180 )

   Color #2: Black

4. Add this file as a diffuse map ( Maps > Standard > Bitmap > concrete-texture-high-resolution.jpg )

And here is how the rendered interior with default lighting looks like:

Step 6 The Main Light Source

Now it’s the time to create the lighting. Let’s start with the main light source (sun). Create Mental Ray area spot ( Create panel > Lights > Standard > mr Area Spot ) in the front viewport. Place the spot light according to the picture below. Modify the spotlight ( Make a selection > Modify panel ) according to the following parameters:

• Spotlight Parameters
  • Hotspot/Beam: 24
  • Falloff/Field: 26
• General Parameters
  • Shadows: On (Ray Tracted Shadows)

( Tip: If you’d like to make the light more directional, just move the spotlight farther away from the warehouse. )

Render the image to see the lighting:

Step 7 The Environment

At the moment we can’t even see the windows because the background color is black (by default). Let’s go to the environment settings ( Rendering > Environment… ) and change the background color:

1. Click ‘None’ and select Glow ( Maps > mental ray > Glow ) from the Material / Map Browser
2. Open Material Editor ( Press ‘m’ in keyboard ). Drag and drop the Glow shader from environment settings to an empty material slot in Material Editor ( make sure to select ‘instance’ when asked ). Make the following adjustments to the Glow shader:

   Glow: White

   Brightness: 4

Render the scene to see the effect:

Now that we can see the windows, let’s apply a glow around them. Apply Glare Camera Shader ( Rendering > Render Setup… > Renderer > Camera Effects > Camera Shaders > Output > Glare ) Just turn the output shader on, the glare shader should be selected by default. Render the image again to see the difference. ( The use of Glare shader is the reason for using Glow shader in the background instead of just white color. )

(The glow effect might seem really strong at the moment but in my opinion it works well in the final image. You can adjust the strength of the glow by adjusting the brightness of the glow shader or by adjusting the glare shader itself.)

Step 8 Indirect Lighting

At the moment we have only the spot light (sun). The image is very dark and there is no indirect light. Create a skylight ( Create panel > Lights > Standard > Skylight ) to simulate the indirect light coming from the windows. Apply ( Make a selection > Modify panel ) the following settings to the skylight:

• Multiplier: 1,5

Render the scene to see the lighting:

Some light reaches the ceiling over the windows but as a whole the image still looks about the same. We need to drive more light inside the warehouse. Fortunately there is an easy way to do just that. Go to the right viewport and create two sky portals ( Create panel > Lights > Photometric > mr Sky Portal ) that are slightly larger than the windows and position them immediately outside the openings. Apply ( Make a selection > Modify panel ) the following parameters to the sky portals:

• Multiplier: 1,5 ( The strength of the light )

( Sky portal needs a skylight to work. It gathers existing sky lighting into the interior scene. The arrow shows the direction of light flow. ) Let’s render the scene to see how the sky portals affect the lighting:

Let’s add bounced light to the equation to see if it makes any difference. Go to the Final Gather setup and apply the following settings ( Rendering > Render setup… > Indirect Illumination > Final Gather ):

• Basic
  • Multiplier: 2 ( the strength of the effect )
  • Bounces: 5 ( a number of bounces indirect illumination does )

Render the scene to see the effect of indirect illumination.

Now there is noticeably more light inside. If you look carefully you can even see each corner of the room.

Step 10 Volume Light

Let’s make the image more interesting by adding some volumetric light rays coming from the windows. Go to the Atmosphere settings ( Rendering > Environment… > Atmosphere ) and add Volume light effect:

1. Click ‘Add…’ button, select ‘Volume Light’ from the list and click ‘OK’
2. Click ‘Pick Light’ and click on the mr area spot we created earlier
3. Density: 20 ( strong effect )

Let’s render to see the effect of the volume light:

Step 11 Completing the Lighting and Rendering with Mental Ray

The Volume light seems to bring too much light into the scene. Let’s fix it by decreasing the Final Gather multiplier:

• Rendering > Render setup… > Indirect Illumination > Final Gather > Multiplier: 1,4

Let’s also adjust the sampling settings to get a more polished render. Go to the render setup and increase antialiasing quality by increasing Mental Ray’s sampling values ( Rendering > Render setup… > Renderer > Sampling Quality ):

• Samples per pixel
  • Minimum: 4
  • Maximum: 64
• Filter
  • Type: Mitchell ( For most scenes the Mitchell filter gives the best results. )

That’s it for today. Thanks for reading!

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