Join Brian Bradley for an in-depth discussion in this video Using light cache, part of V-Ray 3.0 for 3ds Max Essential Training.
- In this video, we're going to work with our interior scene and create a GI solution using V-Ray's Light Cache engine, following the same basic procedure as with our earlier irradiance mapping exercise. The first thing we want to do then is open up the Render Setup dialog using the F10 key, and then come into the GI tab and enable V-Ray's GI systems. As we are focusing on Light Cache in this video, we will want to set that as our primary engine, and again, set the secondary engine to None.
Now the default Light Cache settings, as with irradiance mapping, are designed to give us a fairly decent level of quality from the system, although of course the settings are assuming that we're using Light Cache in its more suitable role as a secondary bounce engine. If we go ahead and take a render though, we will see a couple of things. Firstly, that we do get a very high level of illumination in the render, certainly much brighter than would be the case should we be using irradiance mapping here. This, as we have already mentioned, is because Light Cache rays, like their parent technology photons, automatically perform multiple bounces in the scene, and they do so very quickly indeed.
This is in fact Light Cache's big strength. We can also see that even with a reasonably high Subdivision value of 1,000 set, we are still getting a very blotchy, almost impressionist-looking render, meaning we obviously need to improve the current solution. Well then, about enabling the V-Ray Sky Portal that we used in the irradiance mapping exercise. Well, let's unhide that, make sure that it is both enabled and set to use the simple Sky Portal Mode and then take another render, making certain that we first of all save our current render in case we want to make any comparisons.
Well, things are a little smoother and a little cleaner, so we have probably made enough of a difference for it to be worth our leaving the Sky Portal enabled, but we still couldn't honestly say that we have cleaned up our GI solution in any meaningful kind of way. One thing we perhaps could do then is come to our Light Cache Controls and increase the Subdivision's parameter. Let's try quite a significant jump by going all the way up to a Subdiv value of 3,000, keeping in, mind of course, that in terms of actual samples or rays being used, this is 3,000 multiplied by 3,000, meaning we are now working with something like nine million light cache samples in the scene.
And yet even so, if we go ahead and take another render, we can see that whilst what we get does look much smoother in terms of general noise and still doesn't take that much time at all considering we are using quite a high sample count, the simple truth is that the averaging or blending that Light Cache performs is clearly causing us to lose more and more detail in the scene as we add more and more light cache samples. Of course, we still wouldn't want to use this lighting solution in any final renders.
We could clean things up a little by using both the Pre-filter and Interpolate samples options, but again, neither of these would bring us to the point of being happy to use this Light Cache setup as our primary lighting solution. Unfortunately, the Light Cache engine just isn't, typically speaking, a good choice for use in the primary engine slot. Unless that is, we make use of a unique operating mode of Light Cache and set it up so as to perform as a Progressive path trace system.
This essentially is a brute force way in which we can reconstruct and render light energy found in our scenes. The beauty of this setup is that there really are no parameters that have to be tweaked once we have things up and running, and even doing that is extremely simple. All we need to do is come to the Mode drop-down and select the Progressive path trace option. If we want an unbiased render from the system, we need to set our Sample size to 0.0, and then use our Subdiv parameter to essentially control the quality of our image.
If we take a render now, what we initially see appears to be a typical Light Cache pre-calculation, but it actually isn't. What we are seeing here are the final pixels in this render being drawn as we go, or progressively. In other words, this is not a GI lighting solution that we are looking at, this is the final render. Of course, with the current Subdiv settings, which are in actual fact quite low for a Progressive path trace render, we do get a lot of noise in the scene. So we would really need to increase this if we wanted to produce something that looked reasonably nice.
In fact, if I come to the Rendering Menu, choose the View Image File command and from the RenderOutput Chapter03 folder open up the 03_07_Prorgressive.exr file, you can see what we would get using a Subdiv value here of 15,000. Obviously, this had much higher render times than would be normal when using Light Cache, but we have, as you can see, with almost no parameter tweaking at all produced a nice lighting solution that picks out lots of geometric detail found in the scene.
In conclusion then, we have been able to see in this exercise, why Light Cache is not oftentimes used as a primary bounce engine given that the solutions it produces can be both soft and blotchy, even when using a fairly high Subdivision count. We have at the same time, though, noted that we can enable Progressive path trace mode for Light Cache and actually get a really nice, almost tweak free GI render from the system.
- 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.