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In this video, we'll be taking a deeper look into global illumination with VRay, as far as primary and secondary bounces. We're going to go ahead and open the scene file giscene001, that's available to you through this video. And taking a look in the scene, we've got a simple geometry setup with a box with a little sculpture next to it and a glass cylinder out in front.
We have a blue wall inside, and a green ceiling inside that box, as well as a red backing to our little stepped structure. The whole scene is lit by a single V-Ray light that is enclosed inside a sphere which right now is only one sided. So we can see into this sphere from the outside since global illumination is all about light bouncing we've decided to enclose the entire sphere to allow the light to bounce around inside the scene. In the Render Settings dialog, we'll see that the indirect illumination tab shows that GI, is by default turned off.
We are using a 2.2 gamma where don't affect colors is turned on. And we are also using The V-Ray vfb as well while it is set to SRGV view mode. We'll go ahead with gi turned off. We'll render the camera that is called Render Cam, and see what it looks like with only direct lighting involved.
And as you can see, we have very dark areas where the shadows are. Indeed, because of the single light source, there is no direct light reaching into our little box, nor into our structure on the side. We'll go ahead in the render settings window and turn on GI. We will leave reflected and refractive caustics turned off for the moment and we'll leave everything to its default. Meaning we have a primary balance of irradiance map. However for the secondary bounce, we'll go ahead and set that to none to turn off the secondary bounce.
So with this render we're only getting a primary bounce of light. This is the calculation phase that goes through the light from the radiance map. And this is our result, you can start to see light bouncing around inside our room and inside our structure. Comparing with our previous render, in the history, you can start to see how A primary bounce starts filling in some of these enclosed areas. This has helped in part by the fact that we have and overall dome or sphere that encompasses the entire scene, allowing more of the light to be captured throughout the scene.
Well we can see here, now, adding a secondary balance will increase the overall illumination in our scene. So, let's go ahead and set our secondary bounce engine to Brute Force. With everything else set to default we'll go ahead and rerender This frame. They'll begin to see that there's an increase in illumination inside the box as well as inside the enclosure during the irradiance map calculation. And as we finish the render and compare it with the previous render in our history you can see the secondary bounce has added quite a bit of illumination to our scene. Its a matter of fact looking inside the box you will see that the secondary bounce has also picked up color bleed coming up from green. Ceiling to the side of our wall.
Now lets go into the render setting and turn on reflective and refractive acoustics. So we have primary bounce of radiant map secondary bounce of blue force and both types of acoustics turned on rendering will allow us to see a little bit of additional light play around where the glass reflective object is showing us a reflective acoustic. Seen in the increasing illumination right here, as well as a refractive caustics shown right here.
Comparing the two, before caustics and after caustics shows you also a slightly increased level of illumination reflecting from the glass cylinder. (SOUND) Different combinations of bounce engines will yield slightly different results with different render times. Getting a proper combination will depend on the scene itself, the objects in the scene and the animation as far as the objects and the camera in this scene. In this video we took a lot at what primary and secondary bounces are, inside a VRay, and how to enable them as well as reflective and refractive caustics.
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