New and Exciting Features of V-Ray 3.0 - A guide to the V-Ray clipper
Paul Hatton takes a look at creating cutaway renders using the new V-Ray clipper in part 6 of his look at the features of V-Ray 3.0...
This tool is absolutely brilliant! Gone are the days of having to fudge cutaways or use substandard tools or workarounds to create those gorgeous cutaway visuals. These types of visuals/videos are more common within the engineering sector as people are keener to communicate the internal workings of pieces of kit. It does however have its place within the architectural market if you want to create a 3D floor plan for example and cut the roof off. We'll delve into how to use this tool in a production workflow and then you can imagine all the amazing possibilities it opens up to you.
What is it?
Simply put it's just a geometry primitive which lets you cut away parts of your scene. It's important to note that this is only a render-time effect and therefore you won't get any feedback in the viewport. This does have a benefit though as it means your actual geometry in no way gets affected and messed up. It can be distinguished therefore from cutting the geometry or using a Boolean operation, thankfully.
A major limitation
Maybe I'm fussy but I would love to have seen this tool extended to be any shape whatsoever rather than just a plane. I'm sure they'll adapt it in future iterations of the renderer and I look forward to that. Having it as a plane is useful but there are occasions when I want a more complex cutaway and I end up having to create several clipping planes to do the job that one single piece of geometry could have done for me. Like I said, maybe I'm being fussy!
I love the V-Ray help files because they are super helpful at detailing the limitations of tools rather than hiding things. I really appreciate this honesty. Couple of points then. Firstly, if you have overlapping triangles then the V-RayClipper may product undesirable artifacts. Use the xView 3ds Max tool to track these down. Secondly, the Clipper works best with closed objects. This warning can be ignored it you've got all your back faces defined correctly.
Creating the plane
Fire 3ds Max up and head over to the ‘Create' panel. Use the drop-down to select ‘V-Ray' and finally select ‘V-RayClipper'. To add it to the scene simply click once in the viewport. It has no size properties so expect it to act more like a V-RayPlane rather than a standard plane. This also means that it is an infinity plane. Keep that in mind when you're fine tuning what it cuts through.
Camera rays only
The V-Ray help section states this about this little check-box in the modify panel: "The clipper will affect objects as they are directly seen by the camera, but they will appear unchanged to reflection/refraction/GI rays." I prefer the default of this unchecked as it seems to make most sense. I get unpredictable results if I tick it.
Clip lights geometry
I've never used this option but essentially if checked your Clipper plane will not only clip geometry but it'll also clip the lights in your scene. I usually set my scene up to render correctly and then clip the geometry rather than clipping the lights as well. I prefer the control of turning lights on and off if I don't want them to affect my scene.
Use object material
If this checkbox is ticked then V-Ray will go ahead and fill in the cut object with the material that is applied to the cut object. If on the other hand it is not checked then the cut part of the object will inherit the material of the V-RayClipper object. For me it generally makes sense to use the objects material but there are occasions when you want the cut away to be a different material so this is a good option to have.
Set material ID
If you feel a little limited by either using the material of the object or the V-Ray clipper object then make use of the ‘Set material ID' option. When enabled it lets you specify a face material ID. This is the ID that you can then put into a multi/sub object material to specify a different filled material. Really clever little addition to the toolset which gives us users even more flexibility about what the end product looks like.
Really simple, any object within your scene can be excluded from the effects of the V-Ray clipper. I'm really glad V-Ray decided to include this feature because it gives you the required control to be able to set up your cutaways exactly as you need them to be. Just click on the button and transfer any objects across that you want excluded. You can remove them again at any time if you change your mind. Naming your objects intelligently is recommended if you want to use this feature, especially on large and complex scenes.
All in all this is a great first iteration of the tool. V-Ray even improved it in version 3.1 by adjusting the underlying algorithm so it's clearly on their agenda. I can't say I've noticed any improvements to speed because of this but maybe it's just more stable, especially on complex scenes. Generally, I really like this tool and how reliable it is. Thankfully it's nothing like a Boolean tool which could crash on you at any time. Because it's a render-time effect it'll avoid those hair pulling situations of annoying crashes.
Top Tip: Animate the clipper
The clipper can also be animated which means that you can have a cut away which changes over time. Just set up some key position frames and render away! Experimenting with this can give some really cool effects.
Top Tip: Use with Solid Works
Most of our clients who want cutaways are in the engineering sector. Simply import their Solid Works files into 3ds Max, set up the cut away and deliver gorgeous and effective renderings to a very happy client!
New and exciting features of V-Ray 3.0
V-Ray 3.0: New Features: New and Improved Shaders
V-Ray 3.0: New Features: V-Ray RT explained
V-Ray 3.0: New Features: Interface and Frame Buffer
V-Ray 3.0: New Features - Faster Rendering