✱ Q&A: Troubleshooting Emitter Lights in Maxwell Render for Beginners

I got an email regarding troubleshooting emitter lights in SketchUp using Maxwell Render over the weekend, and I thought I'd post my answers here because it could be useful for you. Lots of people struggle with emitter lights when they're first starting out using Maxwell Render and think that the software just doesn't work when in fact you're probably just used to the brute-force techniques required by other rendering programs. I know this because that's what happened to me when I first tried using emitters in Maxwell. 

Here's the Q&A:

Dear Evan,

We are lighting specialists and I am starting to use the Maxwell plugin for Sketchup, for the 3D rendering for our clients. So my issues with the plugin are mostly regarding lightings.

So I played around with the plug in and what’s brothering me is I am not able to create a lighting point even though the material has been set to emitting surface.

Do you know what is there problem, it is frustrating…

Thanks in advance!

There are many variables that could lead to this, so my answer may not lead to a solution immediately. It's going to take some trial and error depending on where you are in your learning process/experience. I’ll do my best with the information you’ve provided. I had the same problems the first time I tried to make interior lighting, so you’re not alone. Here’s my take:

Maxwell is expecting real world values for everything including (1) emitter values, the (2) direction of the polygons that are emitting light, and (3) the exposure values for the camera. 

1. Make sure your light-emitting geometry is about the same size as the real world bulb. Some people make the geometry too small. It needs to match the real world properties of the bulb in terms of size so there is sufficient surface area for the light to flow out of. If the bulb you’re trying to emulate is a globe or curved glass, it’s best to simplify it. My advice would be to start with a simple rectangle and learn how everything works before trying to get it to work in a complicated scene. Once you understand the process, you’ll be off and running. 

I have a tutorial on emitters here (3 parts) that cover this in FormZ. Even though you are using SketchUp, the same methods and lessons apply, so check them out. 

Part 1 | Part 2 | Part 3

2. Make sure the direction of the polygon normals are facing the direction you want the light to go (I covered this in the 3-part video series above). In SketchUp, use the Monochrome display mode to see whether your faces are facing the right direction. Select a face, right click it, and select the Reverse Face option from the contextual menu. If a face turns purple, it’s backwards. This is not what you want to see. Instead, you want to see the white side of the face. Reverse it so you get light coming out of the face. See below:

In SketchUp:


In FormZ:

Click to enlarge


3. Camera exposure is key. If you have a bright environment, you’ll never see the light, just like in the real world. If you’re in a daylit environment, with a physical sky, it will drown out any emitter light. I have a tutorial about understanding exposure in Maxwell here.

Even though it’s formZ and not SketchUp, the same rules apply. You might have to really crank up the wattage of the material to see it initially but after you get your exposure right, you’ll probably be able to turn the wattage down to real world values and get the illumination you want.

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