Lighting Tutorials > Indoor Lighting Analysis >
Adding a Light Meter

In this lesson, you will use the Lighting Analysis Assistant to check your scene’s render settings, then make the needed adjustments so that lighting analysis can take place.

Next, you’ll create an invisible Light Meter object. Light Meters perform lighting analysis by calculating luminance over a specific area in a scene. Light Meters can calculate direct luminance, indirect luminance, or a combination of the two.

Set up the lesson:

- Continue working with the scene from the previous lesson, or open arena_01.max.

Open the Lighting Analysis Assistant and check the status of the scene:

1. From the main menu, choose Lighting Analysis Lighting Analysis Assistant.

   3ds Max Design opens the Lighting Analysis Assistant dialog. This is where you activate and edit the tools used to analyze lighting in a scene.

   NoteThe Lighting Analysis Assistant is available in 3ds Max Design only.

   The status line at the bottom of the dialog indicates the number of invalid settings, if any, that you must correct.

2. Go to the Materials tab.

   The Lighting Analysis tool requires that all objects in the scene use physically correct surface materials. Only objects assigned the mental ray Arch & Design material or one of the Autodesk Materials (including materials from the Autodesk Material Library) are permitted. All other materials are considered invalid. Objects with no material assigned are also treated as invalid.

   The Materials rollout Total Objects With Invalid Materials box indicates the presence of 875 invalid objects in the scene, which you must now correct.

Locate the objects with invalid materials:

1. Click the selection button next to Total Objects With Invalid Materials.

   This selects all objects in the scene that have an invalid material. As you can see in the viewports, most of the problem objects are the arena seats.

2. Right-click an empty gray area of the main toolbar and choose Layers.

   3ds Max Design opens the Layers toolbar. A layer called Seats has already been created for you.

3. Open the layer list and choose Seats from the list.
4. On the Layers toolbar, click (Select Objects In Current Layer).

   All seat objects are selected. On the Modify panel, you can see that 874 objects are selected: This is just one object short of the 875 total number of objects with invalid materials.

Update the material for the arena seats:

1. Open the Slate Material Editor.
2. In the Material/Map Browser panel on the left, locate the Seats material. Drag this entry into the active View. When 3ds Max Design prompts you to use a copy or an instance, make sure Instance is chosen, then click OK.

   The Seats material is a Standard material, which is not physically-based, as the Lighting Analysis Assistant requires.

3. Double-click the Seats material node so you can see the material’s parameters in the Parameter Editor panel on the right.
4. On the Blinn Basic Parameters rollout, right-click the Diffuse color swatch and choose Copy.

   This saves the color for use in the new material you will now apply to the seats.

5. In the Material/Map Browser panel, navigate to the Materials mental ray group. Drag an Arch & Design entry from the Browser into the active View.
6. Double-click the Arch & Design material node so you can see its parameters.
7. Name this new material Arena Seats.
8. On the Templates rollout, choose Matte Finish from the list.

   This gives the material a neutral reflectivity.

9. In the Main Material Parameters rollout Diffuse group, right-click the Color swatch and choose Paste.

   This copies the color from the Standard material to the Arch & Design material.

10. On the Slate Material Editor toolbar, click (Assign Material To Selection).
11. Minimize the Slate Material Editor.

Apply a material to the Ground object:

1. On the Lighting Analysis Assistant dialog, click Update Status.

   On the Materials rollout, the Total Objects With Invalid Materials field updates to show only one remaining object with an invalid material.

2. Click the selection button.

   3ds Max Design selects the Ground object, which is the ground on which the indoor arena stands.

3. To see the Ground object, minimize the Lighting Analysis Assistant, activate the Top viewport, and click (Zoom Extents).

   Top view of scene with Ground object selected

4. Restore the Slate Material Editor window, and move it or resize it so you can see most of the Top viewport.
5. On the Slate Material Editor toolbar, click (Pick Material From Object) and position the eyedropper cursor over a grid line of the Ground object.

   The eyedropper barrel is empty, indicating that no material exists. If you position the eyedropper over another object in the arena model it appears full, indicating that a material is present.

   Because the ground object has no material applied to it, it is considered to have an invalid material.

6. Drag an Arch & Design entry from the Browser into the active View.
7. Double-click the new material node so you can see its parameters.
8. Change the name of the new material to Ground - Neutral.
9. On the Templates rollout, choose Matte Finish from the list.

   This gives the material a neutral reflectivity.

10. In the Main Material Parameters rollout Diffuse group, click the Color swatch.
11. On the Color Selector, change the HSV Value to 0.2.

    This gives the material low reflectivity.

12. On the Slate Material Editor toolbar, click (Assign Material To Selection) to apply the material to the Ground object.
13. Close the Slate Material Editor.

Check the Lighting Analysis status again:

- On the Lighting Analysis Assistant, click Update Status.

  Now the status line should display “Status: 0 Invalid Settings.”

  Now that you have set up the scene properly, you can create a Light Meter. For lighting analysis to take place, at least one Light Meter must be present in the scene.

Create a Light Meter:

1. From the Layers toolbar Layers list, choose Light Meters.

   Any Light Meter you now create will be added to this layer for easy selection later on.

2. Activate the Top viewport, and press Alt+W to maximize it.
3. Zoom in so you can see the floor plan of the arena.

   Now you will create a Light Meter for the tennis court area.

4. On the Lighting Analysis Assistant dialog, go to the Analysis Output panel and on the Light Meters rollout, click Create A Light Meter.
5. In the Top viewport, create the Light Meter by clicking the bottom left corner of the tennis court, then dragging diagonally until the Light Meter gizmo covers the entire surface of the court. Release the mouse.

   Tennis court surface to receive lighting analysis

6. Right-click to end creation of the Light Meter helper object.

   By default, 3ds Max Design creates a 3 x 3 grid of light sampling points. You need to increase the sampling density.

Adjust the Light Meter settings and position:

1. Press Alt+W to return to a four-viewport view, and in the Modify panel Parameters rollout Dimensions group, set Length Segs to 9 and Width Segs to 11.

   In the viewports, you can see each light sampling point as a vertical arrow. Because Light Meters are helper objects, you can move them around like any other object in a scene.

2. In the Camera01 viewport, notice how the Light Meter sample points appear slightly embedded in the court surface. This might hinder their ability to analyze light, so you need to raise them slightly upward.

   Light Meter helper object with sampling points embedded in court surface

3. On the main toolbar, click (Select And Move), then in the Z-axis transform field, type 0.055 and press Enter.

   Light Meter helper object after adjustment of its Z-axis position

   The ground object is five centimeters thick, so the 0.055 value places the sampling points a half centimeter above it.

Save your work:

- Save the scene as my_tennis_court_light_meter.max.

Next

Analyzing the Lighting