Using Radiosity Adaptive Subdivision

Set up the lesson:

• Continue working on your file from the previous lesson or go to the File menu, choose Open and navigate to the \tutorials\scene_management folder. Highlight balcony_radiosity.max and click Open. The scene shows the resulting file from the previous lesson.

Setting the radiosity engine:

1. From the Rendering menu, choose Advanced Lighting > Radiosity. Ensure Radiosity is selected in drop-down list in the Select Advanced Lighting rollout.

   

2. In the Radiosity Processing Parameters rollout, set the Initial quality value to 50%.

   This will make the calculation faster but less accurate.

3. In the Interactive Tools group, set both Indirect and Direct light filtering to 2.

   This will smooth any noise patterns in the shadow areas.

4. Expand the Radiosity Meshing Parameters rollout.

   The scene is mostly made of simple geometry for the walls, floor, roof, etc. which needs to be subdivided because radiosity works by vertex-coloring the geometry. The more vertices in the scene, the better the solution.

5. In the Global Subdivision Settings group, turn on Enabled, and turn off Use Adaptive Subdivision. You will first experiment the effect of subdivision in global mode.

6. In the Camera viewport, right-click the Camera01 label and choose Edged Faces. This will make it easier to see the effect of subdivision in the viewport.

   

7. In the Radiosity Processing Parameters rollout, click Start to begin the radiosity calculation. Once the solution is calculated, you can see its effect in the viewports.

   

   Note: Notice how the subdivisions are fairly equal in size. In this case, the default subdivision size of 3 feet is not enough to catch the subtle effects of hotspots and shadows created by the sun's rays. You could, of course, decrease the subdivision value globally, but it’s better to use an Adaptive subdivision that would divide the geometry in a finer grid only where it is needed.

8. In the Radiosity Meshing Parameters rollout, turn on the Use Adaptive Subdivision option.

9. In the Mesh Settings group, set the Maximum Mesh Size to 2’0.0” and the Minimum Mesh Size to 0’4.0”.

   In the Radiosity Processing Parameters of the Advanced Lighting dialog, notice the message that the solution is now invalid and needs to be recalculated.

   

10. Click Reset All. If a warning dialog appears, click Yes to dismiss it, and then click Start to begin the radiosity calculation again.

    

    Once the solution is calculated, you can see that the divisions are more irregular, and relate mostly to the shifts in lighting, such as where the sun's rays hit the surfaces of the walls and floor.

11. With the Camera viewport active, press F4 to turn off Edged Faces mode. Notice that even in the viewport, you can see the effects of Adaptive Subdivision on the floor as it shows the effects of the sun’s hotspot.

    

12. Render the Camera viewport to see the results.