New and Exciting Features of V-Ray 3.0
Today we're going to look at how V-Ray Render Masks can be used to customise the rendering process...
This is a relatively basic part of V-Ray to get your head around but for us as a studio it has been an absolute game changer for us. We use this every day now and it saves us stacks of time. In previous releases I thought it would be great if V-Ray introduced some sort of marquee select render selection tool but this ‘Render Masks' tool is so much more extensive. It's extremely powerful and I'd urge you to start using it.
What is a Render Mask
If you've been in the CGI industry for any length of time then you'll have come across masks. They are grayscale images that enable you to affect the opacity of other layers or of effects etc. In the instance of Render Masks, V-Ray have given us a tool to enable us to have far greater control over what part of the image we would like to render or re-render. In the background it's working like a black-and-white mask which controls whether something is rendered or not.
Can't I just use the render region
As I said previously, I was always massively frustrated by the render region tool in that you couldn't be more specific. You would have to wait for pointless buckets to render before you finally reached the required section. It was such a waste of time. Render region is in no way intelligent, instead it gives you limited control over what is re-rendered. Render Masks give you a tonne more control and opens up some pretty cool possibilities which we'll explore.
Where is the tool found
If you make V-Ray your render engine of choice and head over to the ‘V-Ray' tab then you'll noticed a rollout called Image sample (Anti-aliasing). Next to the Min shading rate you'll notice a drop-down box for the ‘Render Mask'. This is where you select the type of Render Mask you want to use. There is a button below it which is grayed out by default but we'll see that this area gives you options depending on which render mask you choose.
Option 1: Texture
This first option I hardly ever use but it's nice to have the option all the same. In essence it lets you input a black-and-white image to control what is rendered. This must be a black-and-white image so think of it like turning certain areas on and other areas off. It won't render areas at 50% Opacity if you use a texture with 50% gray, although that would be a nice option to have!
Option 2: Selected
This is by far our most used option. It lets you select one or more objects in the viewport, and when you hit render it does an amazing job of only rendering the pixels for that object. This is incredibly useful if you just want to change the texture of a section of your model. Or maybe you have a batch of car renders for example but the only difference is the paint color – you could make use of this option.
Option 3: Include/Exclude list
The idea of Include/Exclude has been around in 3ds Max for years now so hopefully it's familiar to you. This technique is even easier if you get into the good habit of naming your objects logically consistently. You'll notice that when you choose this option the button turns into an ‘Include…' button. If you press it then you'll get your standard dialogue box. This tool can be especially useful if you've imported objects from something like Revit which has standard naming conventions for different objects.
Option 4: Layers
This is very similar to the Include/Exclude list except the decision making is done based on layers. As a studio we have a system for layer naming so this option is perfect for us. Selecting it will change the button again, and if you press it, it will give you the option to select the layers you want to render. Utilize the standard Click+Shift or Click+Ctrl to make multiple selections. You might want to stay away from this option if your layer naming is all over the place!
As far as I'm aware this is a new addition that was introduced with V-Ray version 3.2, so if you don't have it then that may explain why. In all honestly we don't utilize Object IDs in our day-to-day workflow, but if you do then this makes for a perfect rendering solution. Select it from the list and type in your desired Object IDs with a comma separating them.
You'll probably have realized by now but there is one unavoidable limitation to utilizing Render Masks, and that is the fact that re-rendering a part of the model with different textures for example would ordinarily have an effect on the rest of image, which may not be part of the re-render. So for example, if you change the car paint color then that will affect both GI and reflections. If you use Render Masks though, this will not be picked up in the rest of the image so it's worth just making sure that your image still looks right.
Let me encourage you to make Render Masks a part of your normal workflow. We have saved countless hours of pointless rendering time by adopting the use of this simple tool. Do take a look at my two top tips for render masks to see how you can further utilize this wonderful new tool. Thank you Chaos Group!
Top tip 1: Render masks and videos
These are perfect for videos as well, not just still images. Don't worry if you're selected object goes behind another object, it will all render correctly.
Top tip 2: Good for rendering PNGs
If you want to easily render out a sequence of images to place over your back plate, then just select the objects you want to render, render them, save as PNGs and then place them over the top. No need for grayscale masks!