VRay - Render_Settings

BAS ASIC ICSS OF THE V-R -RA AY RENDER SETTINGS author:

Wout outer er Wynen

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INTRODUCTION This tutorial will explain very briefly many of the V-Ray render settings. A very basic 3D Studio Max knowledge is needed to be able to follow the tutorial. For more info on each topic, please refer to the online manual. It’s also a good thing if you have a basic understanding of  rendering in general. Terms like Global Illumination, raytracing, antialiasing, displacement and so on should sound familiar before you start working with V-Ray. The V-Ray version I used for this tutorial is 1.47.03.

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1. Set V-Ray as the production renderer Open the render settings dialog. Then, go to the current renderer rollout and click  the assign button for production renderer. Choose V-Ray from the list.

2. Extra rollouts! After V-Ray has been set as the main renderer, you’ll notice a lot of new rollouts. Every rollout with “V-Ray” in front of its name is filled with V-Ray render settings... The next steps will each cover one rollout in general.

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Basics of the V-Ray Render Settings

3. V-Ray frame buffer When enabled, the V-Ray frame buffer replaces the Max virtual frame buffer. The V-Ray frame buffer has many more options to post process images and lots of other interesting settings. In this rollout you can control the size of it by disabling the ‘get resolution from max’ check box. Rendering to V-Ray raw image file enables you to render very high resolution images, without eating up all the available RAM. The use of the V-Ray frame buffer is for advanced V-Ray users only. Don’t bother using it when you’re new to V-Ray.

4. V-Ray global switches Here you can control and override many of V-ray’s settings, mainly used to speed up test rendering. You can turn off all displacement, lights, default max lights, hidden lights and shadows by just unchecking the appropriate check box! The “don’t render final image” button is used to let V-Ray only compute the GI (irradiance map for example) without actually rendering the image. Forget this for now :-) Turn all reflections and refractions in the scene on or off by unchecking the check box. Very useful for testing purposes. The max depth controls the depth of  the reflection/refraction (the number of times a ray can reflect/refract before it is being ignored in the raytracing process). Basics of the V-Ray Render Settings

You can also turn off all maps, all filtering of maps etc... Glossy effects are for example blurry reflections or refractions. Turning them off  greatly improves render time, very neat while doing test renders. Override material can be used to give every object in the scene the same material. Secondary ray bias: please refer to the manual.

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5. Image sampler (Antialiasing) In V-Ray, you can choose between 3 types of image samplers to compute the anti aliasing of the image. This controls how sharp and smooth your image will be, and has a huge effect on render times! Fixed rate is very predictable, but slow in many cases. Use this one if there are a lot of glossy materials, area shadows, motion blur etc... Higher subdivs means better quality, higher render times. Adaptive QMC is my favorite. As it’s name already indicates, it is an adaptive sampler, it will adapt its calculation to the situation. It will compare the quality of  the computed pixel by some thresholds, and decide if it’s good enough or if there are more calculation needed. This samplers quality is controlled by the QMC rollout (further down in the rollouts). Use adaptive QMC if you have many glossies, area shadows, motion blur etc. in your scene, and if you want maximum control over the speed vs quality of the image. It takes some time to get a grip on it, but once you get it, you have full control over V-Ray with just a few clicks.

Some testing will be needed to understand the differences between the 3 samplers. The online documents have very good explanations on this topic, with lots of examples showing all differences. The anti aliasing filter can be changed if  you have problems with fine textures or fine details in the scene. Every sampler has its own characteristics, but it is not the goal of this tutorial to explain them all. In many cases you can get away with simply turning the filter off! A few filters I use often: - none - Mitchell-Netravali: smooth result, good controls - Catmull-Rom: very sharp (a bit like the result of ‘unsharp mask’ in Photoshop) - soften with radius around 2.5 (smooth and fast)

Adaptive subdivision is also an adaptive method. Although very fast is many cases, it can get very slow with lots of glossy effects in the scene. It also uses more RAM memory while rendering. Use this sampler if you have large smooth areas in your scene (for example an interior with large white walls). The min/max rates control the quality, 0/2 are good values, -2/-1 are good for very fast test renders.

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Basics of the V-Ray Render Settings

6. Indirect illumination (GI) This rollout controls the main options for the GI (bounced light). Like most GI renderers, V-Ray makes a difference between first and secondary bounces. A simple spotlight will cast direct light. This light hits an object and will be absorbed a bit, but the rest bounces back into the scene. This is the first bounce. This first bounce will probably hit another object and will bounce again (second bounce) and so on until no energy is left. The direct light and first bounce will have the largest impact on the lighting look, because this bounced light has still a lot of energy. So these need to be computed very accurately to create realistic lighting. The secondary bounces are usually less important (a lot of the light energy is already absorbed, there’s less impact on the visual result), so approximations can be rougher here (interior scenes are an exception, the secondary bounces become important too).

or off with the two appropriate check  boxes. An example of very visible reflective caustics is the light pattern you will see if you put a spotlight on a chrome ring lying on a table. Refractive caustics are generated for example by a glass sphere, which bundles all light that passes through it, creating a very bright spot underneath it. Note that when you want GI light to pass trough transparent objects, you must set ‘refractive GI’ caustics ON!

You can choose between different ways of computing first and second bounces, and adjust the strength of  them (multipliers). Post processing options can desaturate the GI light, or its contrast. Remember that caustics is only a name for refracted/reflected light. Because light coming from a max spotlight, for example, is direct light and not GI light, you also have the ability in V-ray to render these direct light caustics.

Caustics are light patterns formed by refracted/reflected light. GI caustics are caustics created by refracted/ reflected GI light (light bounces). The standard first and secondary bounces don’t take the reflective/refractive material properties into account, only the diffuse properties. You need to turn them on

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7. Irradiance map / Quasi-Monte Carlo / photon mapping / light cache Depending on the method for first and secondary bounces you have chosen, the above rollouts will appear. They are all ways of  calculating GI bounces. Each have their specific advantages and uses. I will explain these in a separate tutorial as this is too complicated for this basic settings overview. For now, remember that all these methods are ways to approximate GI lighting. GI calculations are very time consuming, that’s why methods are invented to speed things up by using approximate values.

8. Caustics Remember the direct light caustics from step 6? Well, here you can turn them on or off, and control some parameters. To get nice direct light caustics, you will also need to make adjustments in the V-Ray light settings. If I find the time, I will make a direct caustics tutorial too! A simple trick to eliminate the need for direct light caustics, is simply not to use direct lights. With only GI light, you tick  ‘refractive/reflective GI caustics’ in the Indirect Illumination rollout and all caustics will be calculated according to your GI settings! Of course it is not always possible to use only GI light...

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Basics of the V-Ray Render Settings

9. Environment V-Ray allows you to override the Max environment with these controls. Use the skylight to light the scene with a ‘skylight’. If you put a map in the slot behind it, the color swatch is neglected and instead, the map is used to light the scene. You need to enable GI for the skylight to become visible. The skylight is not a direct light, it’s actually treated as first bounce, that’s why GI is needed to make the skylight visible. Note that if GI is enabled, skylight is turned off and you have put a color in the Max background, that color will be used as skylight! The other swatch controls the reflection/ refraction environment. No matter what the max environment is, your objects will always reflect/refract this V-Ray override. You can also put a map in there like with the skylight option.

*Note that these settings will not show up in the background of the render. Use the Max  environment setting for this.

10. QMC Sampler The QMC sampler can be seen as a global quality control center. It controls all parameters that have anything to do with Quasi Monte Carlo calculations like adaptive QMC AA, QMC GI, Irradiance map, Glossy effects, area shadows, Motion Blur and Depth of  field. The most important parameter is the noise threshold, this controls the accuracy of al the calculations. The highest quality setting is 0.001, but this of course requires the longest render time. The global subdivs multiplier can be used to lower/increase all subdivision parameters in the scene (Irradiance map, QMC GI, glossies, area shadows, Motion Blur, Depth of field,...). This is very useful for fast test renders.

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11. Color mapping Color mapping can be used to post process an image within V-Ray. Please refer to the manual for more information about the different types.

12. Camera You can choose different camera types instead of the default standard Max camera, for example fish eye lens, spherical camera, cylindrical etc... Please refer to the manual for more information about these different camera types. Depth of field is an effect caused by the diameter of the diaphragm opening of the camera. Objects that are out of focus will become blurred. The further away from focus and the bigger the diaphragm, the more the object will be blurred. Motion blur is the blur that you get when objects move very fast, or when the camera is moving. Both of these effects are raytraced, not faked with some fancy tricks, so they have a big impact on render times...

13. Default displacement These parameters control the default V-Ray displacement settings. More on displacement can be found in the online manual, with lots of illustrations.

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Basics of the V-Ray Render Settings

14. System Another rollout that controls all kinds of general parameters. Raycaster parameters are used to control the amount of memory V-Ray uses for a specific scene. In 99% of all cases you don’t need to touch these! Render region division X and Y control the width and height of a render bucket. For small render resolutions, you can lower these, for high resolutions you can increase these. Good values are squares between 32 and 128px. Region sequence alters the order in which the buckets get rendered. Distributed rendering is the process of  rendering one image with different PC’s. “Previous render” controls how the previous render in the frame buffer is overwritten by the new buckets. Default geometry static/dynamic: refer to the manual.

Frame stamp is useful to print render times and such on the rendered image. Objects and lights settings control V-Ray specific properties for scene objects and lights. You can turn on/off all kinds of things locally for each object in the scene. Presets can save all or some render settings for easy and quick  switching between for example test settings or high quality settings. The V-Ray log is the small window that appears while rendering, giving you some textual feedback about the rendering process. The level controls how much feedback is printed inside the box.

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