Indeed, you would use a grayscale image with your lights UV-mapped in another app to the correct position and load it into the Luminosity channel of the Default Shader that corresponds to your lights UV group after the model loads in TG (meaning, you have to create the light textures and align them correctly in another app that handles UV mapping first). Then adjust the Luminosity value until you get enough light - you may need quite high values, e.g. above 1 (perhaps well above 1), depending on the scene, size of model, etc. Also, you may need higher GI settings to get best results, something like 4/4 or 6/6 (cache detail/sample quality).
- Oshyan