Hey guys! Welcome to Part II of the V-Ray for Sketchup series. In Part I we discussed the V-Ray Basics: what it is, what it looks like, and what all the little yellow and blue buttons mean. As a forewarning, this series is for students and practicing professionals that need to produce images quick, but don't necessarily need to understand the ins and outs the process. This post will explain what to do and how to do it, but it won't necessarily explain why. Consider yourself warned!
The Options Editor
Getting familiar with the Options Editor is the best way to boost your program confidence and produce the best renderings possible. Using the right settings you can optimize your light output, render faster, and produce higher quality images. You don't have to know what every single option means, but I think it's helpful to have a general idea of what types of settings are in each category, and get acquainted with the more important ones.
This section allows you to override all settings in the model. It allows you to turn off all lights, shadows, reflections, or materials in the entire drawing by simply checking or unchecking a box. This can be helpful when your materials are taking too long to render and you need to get your lighting sorted. Just check "Override Materials" and render.
The only thing I use System for is adjusting the Render Region Division and Dynamic Memory Limit. Setting the Render Region Division cuts down on render time, but I have no idea why (but this guy does). His rule of thumb is to set the X and Y figures to 10% of your total resolution instead of the default 32. If you are test rendering at 800 x 600, set your RRD to 80. If you're rendering at 1024 x 768, set it to 100.
The other important setting in the System tab is the Dynamic Memory Limit. I swear, people don't talk about it outside CG artist forums, but it's actually a huge deal. When a computer renders an image it uses memory to power the operation. The Dynamic Memory Limit controls how much memory your computer is allowed to use. In other words, if your rendering needs 10GB to render and you only have 8GB on your computer, it will crash. If your computer has 32GB, if your DML is still set to 8GB, it will still crash because it is not being allowed to access it's full memory potential. DML is measured in MB so if you have 16GB on your computer and want to use half of your memory, set your DML to 8000.
In my opinion, Camera settings are the single most important adjustment you can make when setting up a rendering. Basically, it allows you to adjust the brightness of an image the same way you would on a real camera: using ISO, Shutter Speed, and the F-Stop. Make sure your "Physical Camera" setting is checked on, along with your "Exposure" setting. The only three settings I change are the three mentioned above.
If you are unfamiliar with manual camera settings, here is what you need to know. Technically these settings control how blurry, focused, or grainy a photo is, but they also control how bright the final image is. Never mind why or how, all you need to know is what will make your image brighter and what will make it darker. For reference, I made this handy little cheat sheet below.
I don't typically fuss with Environment settings, because I only render interior scenes. I treat the sunlight as if it were natural daylight and manipulate camera settings to get the exposure I want. The angle of the sun and shadows can be controlled through the regular Sketchup Shadows toolbar.
This is where things get complicated and where V-Ray tutorials start to seem like they were written in a different language. Basically, the Image Sampler addresses the jagged lines that can appear in a rendering. Minimizing this effect is called Anti-Aliasing, and can really only be described using a picture (see below). Do you see how the anti aliased line subtly blurs the jagged corners to make it look smoother? That's what we want.
Quite a bit of computer magic goes into to this process, but it's really confusing and hard to explain. So I will leave you with this: Set your "type" to Adaptive DMC, and leave the Anti aliasing filter to "Area." You can read more about this in this article, but as long as you leave these settings you won't really need to. Or at least I don't.
I honestly don't know what this is. However, I do know that my favorite VRay tutorials always set the "Noise" to .001 so I do too.
As you might have been able to guess, this controls the colors in an image. 99% of the tutorials I watch use "Reinhard" so I do too. If anything else needs tweaking I Photoshop it later.
Here's what it looks like, but I literally never touch it. I wasn't kidding when I said this tutorial would drive CG artists crazy!
This is where you choose what size image you want to render. One thing to note, however, is that Sketchup Scene dimensions are not the same shape as the options listed (640 x 480, 800x 600, etc). When you export a JPEG out of Sketchup, it is rectangular. A 800 x 600 sized image is closer to a square and will cut off some of your image. To get the same aspect ratio, you have to click "Get View Aspect" and it will adjust automatically.
The only thing I pay attention to in this menu is "Ambient Occlusion." It takes FOREVER to render, but if your shadows just aren't rendering as realistically as you want them to, you might have to bite the bullet and turn it on.
The best visual explanation of Ambient Occlusion is this photo below from a fantastic blog called Visualizing Architecture. As you can see below, adding AO gives the shadows more depth and makes them look much more life like. This effect can also be done in Photoshop, but sometimes it's nice to have the computer do it for you.
Irradiance Map, Light Cache, and Caustics, and RT Engine
I never touch these, but here is what they look like:
We can talk about what displacement is later, but this menu allows you to override individaul Material settings with the click of a button.
Whew! Did you get all that? If you want to keep researching the mechanics of the rendering process, I recommend the sites listed below. The people behind these sites have probably forgotten more than I will ever know and have great photo references:
If you just joined us in the V-Ray Series, here is a link back to Part I where we went over the basics: what it is, and what the menu bar looks like:
Good luck and stay tuned for more posts in this series!