Study in indoor lighting with sunlight from a window, Max 9

At each final gather point mental ray shoots a bundle of rays into the scene to check how much light is hitting the point. You control the number of rays with the Rays Per FG Point setting.

Interpolate FG Points:

This determines how many FG points are used to compute the final result.

Increasing this number does not make a great cost on render time.

Interpolate FG Points: 1

 

Interpolate FG Points: 5

Interpolate FG Points: 30

Interpolate FG Points: 200

Initial FG Point Density

(this controls lighting detail)

Higher density shows more detail. Whenever you need more detail in a scene, increase the density, from .1 to 4.0 here:

SLOW ... good for detail, not good for smooth

Rays per FG Point

Set to 1:

Set to 5

Set to 100

Now to 1,000

Starting to slow down ... 10 minutes ... note the light spreading into the room ...

10,000 ... slow ... 1 hour.

Very nice. The noise in the “Wood Painting” could have been resolved with a higher interpolation number.

More rays are required for scenes like this one, with small bright windows (high contrast inside the scene).

From the Max 9 help file: “Fewer rays are required for a scene with even illumination, like a white office room with many light sources at night (no daylight).”

Typical values are:

for even illumination (low contrast) -- less than 50 rays

average scenes -- 100-500

High-contrast scenes (like this one) 1,000-10,000

Our scene is a perfect situation for using Rays, as all the lights are off and the incoming sunlight is very high contrast.

Multibounce

Set to 5 ... this is a 3 minute render ...

It brightens corners, but too much overall brightness.

Adjusted in advanced lighting:

Same advanced lighting, with the medium preset:

1 hour and 15 minutes:

Adjust brightness ...

Save the fg file ...

Then you can re-work the interpolation or decrease the render size for a faster test...

2.0 Density

250 Rays

50 Interpolation

4, 16 Mitchell

3 hours and 15 minutes:

Take that same file and re-render at 800x600:

(There are obvious issues of polygonal density on the lamp stands and a disappearing top to the spiral sculpture)

2.5 hours:

Interpolate Over Num. FG Points set to 100 to smooth the walls.

We will read from the final gather map ...

1 hour 55 minutes:

An even better image could be achieved by increasing Rays Per FG Point.

We also fix some geometry and reduce by half the output value for the lume glow outdoor image planes.

15 hours and 15 minutes ...

Car paint max 9 on the sculpture, and default Arch/Design glass on the lamp ...

The Interpolation number was too low for smooth walls ...