CGNest Blog

Ive seen a lot of people, usually people just starting in 3D or starting in lightning interior scenes, doing their light the wrong way. GI is a fantastic thing but beginers use it in a wrong way. Not just the beginers, some people are doing interiors for a few years and still do such mistakes. I am not going to write about what GI is, there are a lot of articles on the web on that subject. GI is, among other things, is used to assist with your lightning in a way that it fills in the black parts of your scene. I know that this is not nearly a good explanation what GI is or its the most acurate but its good for this purpose. A lot of people use GI like it is a light source witch is wrong.

Take this scene for example. Ive modeled a very very simple scene here so no modeling awards .  Ive used a vray sphere light to simulate a sunlight and did a render with no GI and it looks like this

Then i turned on GI and had a lit scene.

So basicly in this case what i did is i used GI to light my scene or the way i like to call it, i used GI as a light source. Only sunlight is there and nothing more. There are a lot of things that are wrong here. But most of all the end result is not as good as it can be. And thats what we are interasted the most. In this case if we want more light than we increase bounces or we use color mapping methods like exponental and boost lights and darks in exponental to get a good result but in that case what i find is that the textures are not natural, they are too washed out, too bright/dark and not the way they look on the image.

Photographers have a perfect light source called Natural Sunlight and still do a lot of fakes to make their interior photographs look as good as they can be. So if they have perfect natural light and still dont get the result they are after how can you acheve good result with just GI?

Lets light our scene again. First thing first, skylight. In nature there is no separate lightsource called skylight, its just sunlight bouncing off the air particles. But in 3D we do those lights separately.  So i added a big planar vray light behind the window to simulate a skylight and we get this.

Then i added a sunlight.

Now ive seen a lot of photographs where even in the daylight the lights in the interior (the lamps and so on) are turned on. So lets do that. We have 4 lamps on the front wall and one main light on the ceiling. So lets turn those on.

Now compare the first image in this post to the one above. Notice the diference? And i still haven’t turned on the GI. As ive said before, GI is used to “fill in the gaps” or to bounce the light that is allready in the scene. So lets turn on GI.

Much better than the second image in this post in my opinion.  Perhaps the above image is not the best lit scene you have seen but its a tutorial scene and its there to prove a point. Also now you have control over skylight, sunlight and the interior lights and you can tweek them as needed.

I hope that you can find this post usefull.

Cheers!