Q&A: “What’s a good V-Ray workflow that enables you to tweak your renders quickly?”
James Cutler’s here to help Richard Fox put together a versatile V-Ray workflow; the solution’s elementary
In any project it’s important to maintain a productive workflow that allows for tweaks and amendments to a render without them being too time-consuming. One of the most common is the use of render elements in V-Ray. A final render is made up of various layers that, when composited together, produce what’s known as a beauty pass. By using render elements you can save out each layer as a separate image and then simply tweak a reflection, shadow, diffuse colour and even light intensity.
There are several core render elements that make up a common beauty pass. In Photoshop certain render elements are multiplied, and others are added to complete the beauty pass:
- VRaySpecular (add)
- VRayRefraction (add)
- VRayReflection (add)
- VRayRawLighting (multiply)
- VRayRawGlobalIllumination (add)
- VRayDiffuseFilter (multiply)
When compositing your final render in Photoshop, you need to make sure all your elements are saved as at least 16-bit TIF files so that no colour information or dynamic range is lost.
Faster feedback using active shade in V-Ray RT
One of the other most useful render elements is VRayMtlID. Once a material has been assigned a unique ID, this render element will show an object as a block colour. This enables you to make selections in Photoshop for masking purposes very quickly and easily. Depending on your workflow, you may wish to have your mask antialiased, in which case it would be better to use a different render element such as VRayWireColor. This element will create block colour masks for each object according to their wire colour. However, this will render all objects within the camera view. If you want to render a mask for a single object or a selection of objects, it would be best to assign material IDs and use VRayMtlID.
You can also exclude objects from a render. To do this, select the objects you don’t wish to see in your final render, go to their object properties, and clear the Visible To Camera check box. If you marqueeselect all objects you want to hide you can make them invisible in one click. You may wish to use this method when you need to re-render a particular object, but still have the lighting, reflection and shadow affecting it. You can then overlay this render onto your existing render layers in Photoshop. One of the new features of V-Ray is V-Ray RT. This is an interactive renderer that uses progressive path tracing technology. The render starts at a very low quality, and the longer you leave the rendering process, the cleaner the noise becomes, and the quality of the image improves. You don’t need to worry about settings such as Irradiance Map or Light Cache because these aren’t used in V-Ray RT. This allows for a much simpler rendering process, and the results can be of a production-level quality if you’re prepared to wait.
Set up the render elements in Photoshop
One of the main speed advantages of V-Ray RT over the standard V-Ray renderer is the ability to use GPU rendering. Rendering using the GPU can be much faster than by using the CPU, which allows for almost real-time feedback in your scene.
Another useful feature within V-Ray RT is the Draw Region tool, which is available by right-clicking inside the active shade window. Similar to how Draw Region works in the standard V-Ray renderer, this enables you to draw a small region, which is then recalculated, while the remainder of the scene stays the same. The feedback from V-Ray RT can still be a little slow, particularly on larger scenes such as highly detailed interiors, but the Draw Region tool enables you to work much faster. In all, V-Ray RT enables you to be more interactive when it comes to amending areas within your scene, and you can get good results in very little time.
James Cutler runs MintViz, a fresh-thinking creative studio that creates, shares and educates to deliver inspiring digital media. Model: 248 F1 by Kjdesigns; available at www.the3dstudio.com
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on Monday, September 24th, 2012 at 4:20 pm under Guides, Technique, Tutorials.
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Tags: Photoshop, V-Ray, v-ray rt