Join Brian Bradley for an in-depth discussion in this video How light cache works, part of V-Ray 3.0 for 3ds Max Essential Training.
- If Irradiance mapping can be set to take the prize as V-Ray's most widely-used GI engine in the Primary bounce slot, it is probably safe to say that Light Cache could make the same claim when it comes to being used as a Secondary bounce engine. Light Cache, like Irradiance mapping, is another view-dependent GI technique which means all of the same base limitations apply. The solution is calculated from the rendering camera's position and so if that camera is moved once the GI has been created, we will get holes or gaps in the lighting solution that can only be filled by recalculating the Light Cache all over again.
If we do have animation in our scene, be that moving cameras, moving objects, or both, then we do again have a number of options in the Light Cache rollout that we can work with. In the Mode setting shotdown, we have Fly-through, From file, and Progressive path tracing modes along in the advanced UI with an option to use the Render camera's path when calculating GI, an option that is also available in the Irradiance map's advanced UI as well. These can all help up work around the limitations that exist in the Light Cache system when it comes to using animated or moving elements in our scene.
As we did in our Irradiance mapping exercise then, let's walk through the basics of how Light Cache actually works. To calculate the lighting in an environment, the Light Cache engine will shoot large amounts of rays from the rendering camera's point of view out into the scene. These rays are responsible for creating the required Light Cache samples, the number of which will be controlled by our Light Cache Subdivs parameter. With every hit or intersection of these rays and the geometric surface in the scene, a Light Cache sample will be created.
Now unlike the initial rays used in an Irradiance mapping solution, Light Cache rays can and will bounce a number of times, even when Light Cache is being used in the Primary engine slot. Scene information from each of the subsequent bounces along the rays' path will be recorded and then stored in a 3D point cloud structure, which again is the way that Irradiance mapping also works. If a bouncing ray hits an already created Light Cache sample, then any further tracing of that particular ray gets canceled and information from the already existing and computed Light Cache sample will be used instead.
This, as you can imagine, helps speed up the Light Cache process hugely, as no unnecessary tracing of rays needs to take place, meaning Light Cache is able to calculate a lot of light bounces very quickly indeed, making it an excellent choice for lighting difficult spaces such as interiors which, typically speaking, are much harder to light with a GI solution than exteriors. One interesting aspect of Light Cache is that there is nothing different about a Light Cache solution computed in the Primary engine slot as compared to one calculated in the Secondary slot.
So if we save a Light Cache file to disk, one that has been computed in any of the slots, we can safely load and use it in the other should we want or need to. Of course, Light Cache does have some limitations, like Photon mapping, from which the technology is derived, Light Cache is not adaptive as it is computed at the current render resolution, meaning it is important that this has been set up correctly by us prior to hitting the Render button. Light Cache can also work poorly with bump maps in the scene and so we may need to keep an eye on how these are reacting or behaving as we calculate our GI solution.
In fact, truth to tell, Light Cache really is nowhere near as good as the other GI methods available in V-Ray at picking out small or fine details in a scene. Again then, we would probably want to monitor that aspect of our Light Cache renders very closely indeed.
- Using the new UI elements, Quick Settings, and revamped Frame Buffer
- Understanding color mapping modes
- Adding V-Ray light types
- Working with the V-Ray Sun and Sky systems and dome light
- Using irradiance mapping and light cache
- Working with diffuse color maps
- Making reflective materials
- Creating a translucency effect
- Using the new SSS and skin shaders
- Ensuring quality with image sampling
- Working with the adaptive subdivision engine
- Controlling the physical camera
- Working with FX tools such as VRayFur and VRayMetaball
- Stereoscopic 3D rendering
- Using Render Mask
Skill Level Intermediate
Q: This course was updated on 02/02/2016. What changed?
A: We added tutorials on the new 3ds Max camera tool, which replaces the defunct V-Ray Physical Camera. The author also includes a method for creating a V-Ray camera via scripting.
Q: This course was updated on 04/19/2018. What changed?
A: New videos were added that cover V-Ray 3.1 to 3.3 updates.
SketchUp: Rendering with V-Ray 3with Brian Bradley4h 15m Intermediate
V-Ray: Control Color Bleed in SketchUpwith Brian Bradley1h 2m Intermediate
Introduction and Important Information
V-Ray 3.1 to 3.3 Updates
V-Ray 3.4 to 3.6 Updates
1. Getting Ready to Render with V-Ray
2. Key Lighting Tools
3. Global Illumination
4. V-Ray Materials and Maps
5. Quality Control with Image Sampling
6. Working with Cameras: The V-Ray Physical Camera
7. Working with Cameras: V-Ray 3 & the 3ds Max Physical Camera
8. The V-Ray FX Tools
What's next?1m 47s
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