Mental Ray Lighting (part 3)

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!