Rendering with mental ray: Sky Portal and Exposure Control

Rendering with mental ray: Sky Portal and Exposure Control

Using Sky Portal and Photographic Exposure Control

 

Autodesk 3ds Max Tutorials > Lighting and Rendering >  Rendering with mental ray: Sky Portal and Exposure Control > 

Adding Daylight Illumination

Start by adding daylight illumination to the lounge scene.

Set up the lesson:

1. From the \tutorials\mental_ray folder, open the scene file LoungeBar_Tutorial_Start.max.

   The raw scene is set to render with mental ray.

   

2. Activate the Camera01 viewport, and then on the main toolbar, click Quick Render.

   

   Default lights provide basic illumination and textures and materials have been applied, but the rendered interior appears flat and not very realistic. You need to add daylight to the scene. This will be generated by a daylight system comprising two mental ray photometric light sources:

   • mr Sun, which simulates direct light from the sun.
   • mr Sky, which simulates indirect light created by the scattering of sunlight in the atmosphere.

   These two light sources will be accompanied by the mr Physical Sky environment shader, which establishes the physical representation of the sun and sky.

Create the daylight system:

1. On the Create panel, turn on Systems.
2. On the Object Type rollout, click Daylight.
3. In the Top viewport, click anywhere outside of the wireframe scene and drag in any direction to create a compass rose.
4. Release the mouse button and move the mouse up or down, as shown below. This distances the light source from the compass rose, and makes it easier to select by a click, later on.

   

5. Right-click to end Daylight creation.
6. Right-click the Camera01 viewport and press F9 to render the scene.

   

   The scene appears very washed out because the illumination has not yet been calibrated to the mental ray renderer.

7. Select the Daylight object you just created, then go to the Modify panel.
8. On the Daylight Parameters rollout > Sunlight drop-down list, choose mr Sun, and from the Skylight drop-down list, choose mr Sky.

   

9. A dialog appears, asking if you want to use the mental ray Physical Sky shader. Click Yes to apply the mr Physical Sky shader to the scene.

Set the time and location of the light source:

Now you will reposition the Daylight object, or “sun,” so that its position in the sky corresponds to the geographic location of the scene.

1. With the Daylight object still selected, on the Daylight Parameters rollout, click Setup.

   3ds Max displays the Motion panel.

2. On the Motion panel > Control Parameters rollout > Location group, click Get Location.

   

3. In the Geographic Location dialog, choose Los Angeles, CA as the physical location of the scene, then click OK.

   

   The compass rose and Daylight object are repositioned to scene coordinates that simulate the real-world latitude and longitude of Los Angeles, California.

   The Control Parameters > Time group contains controls that let you modify the date and time of day, which also affects the sun position. For now, leave these values at their default settings: noon on June 21st, the year’s midpoint.

   

4. Press F9 to render the scene.

   

The scene is now too dark; not enough photons are entering the scene to properly illuminate the interior.