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Vray Tutorials

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Vray Basic material settings
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Before you start If you discovered this Vray tutorial page through a direct link or search engine, please note that you're on page 2 of the tutorial! Please complete page 1 first if you haven't done so. This second page is all about refraction!
1. Start a new scene Open 3d studio max and start a new scene. Open the render settings dialog and do the following: - set Vray as the renderer - output size to 480360px - global switches: turn off default lights - image sampler to adaptive QMC - antialising filter "mitchell-netravali" - indirect illumination ON - Secondary bounces multiplier to 0,85 - Irradiance map settings: - "low" preset - hsph subdivs = 20 - environment: - skylight pure white color - reflection/refraction pure black, 1.0 multiplier - system: - render region division 5050 px - frame stamp: delete all except the rendertime part
2. Create the testscene I suggest using the same kind of object as I did. A max teapot is not good now because the mesh has holes in it, it's not 'watertight' and you don't want that on refractive objects. I made this modified torus knot because it will be an interesting shape to test with, because of all the curves and thin/thick areas. If you want, use the exact same settings as I did (click image on the right to see all settings).
3. Create materials Make a medium dark blue Vraymaterial for the groundplane, and a very light grey Vraymaterial for the torus knot and assign them to the corresponding objects. Hit render, you should get something like my example on the right.
4. Refraction parameters Go to the white material and take a look at the refraction parameters. Refraction refers too light rays getting bent when going from one medium to another. For example light travels through air, then hits a glass object and the ray gets bent under a certain angle. Then this ray will travel further through the glass, and eventually will leave it at a certain point, getting bent again. How much a ray gets bent depends on the IOR (index of refraction) of the material. A high IOR means a lot of bending, IOR=1.0 means the rays will not bend. The Vray material has all options available to create any kind of refractive material. As you can see, many options are similar to the reflection parameters. First, change the refract color to a medium grey color.
5. Refraction color Render the image. You will notice the object has a transparent look. The grey refraction color means it's about 50% transparent.
6. Diffuse color Change the diffuse to black and render again. The result is pretty straightforward.
7. Refraction color Change the refraction color to pure white and render. The result looks weird... Because now the object is 100% transparent, the diffuse color has no effect at all anymore. The black regions are rays that get refracted to the environment color, which is black.
8. Adjust reflections The previous step looks weird, because usually materials with such refractive properties are also reflective. If you set the reflection to pure white, and check fresnel reflections, the material looks a lot better. The material you created now is the basic setup for clear glass in Vray.
9. Create an environment The rendering looks very boring, because the only thing to refract/reflect is the groundplane and the black environment color. Create a large, thin box and position it more or less like I did.
10. VrayLightMtl The goal is to turn this box into a light source. An easy way to do this, is by using the special VrayLightMaterial. Click the get material button and choose VrayLightMtl from the list. Assign the material to the box and set the multiplier to 8.0
11. Adjust skylight Hit render. It's way too bright, because our skylight is still active. Set the skylight multiplier to 0.0 and render again. If it's too bright or too dark, you need to play with the Vraylightmaterial multiplier until it looks ok. You can clearly see tha the light is coming from our big box now, and the light source also reflects in the torus knot. The contrast between very bright light and black environment is very good for rendering glass or metal like objects.
12. Refractive GI caustics The light coming from the box is not direct light as with a max spotlight. It is actually treated as first bounce GI (just like the Vray skylight). If you would turn off GI and render, there will be no light at all. Because of this, it is important that you leave the refractive GI caustics in the indirect illumination rollout ON. Try rendering this scene without refractive GI caustics. You'll see the shadows are much darker. The GI light is now unable to pass trough the transparent object (there are no GI caustics). Caustics are noting more than refracted/reflected light. To continue, turn refractive GI caustics On again. Also go to the irradiance map rollout and set the preset to custom. Change the min/max rate to -4/-2 to speed up rendering. Note that the GI will be more blurred now, but since we're only testing, it doesn't matter. There will be more on caustics later on in the tutorial. For now remember that you need to enable the GI caustics if you want GI to pass trough transparent objects.
13. Max depth Increase the max depth parameter in the glass material to 10, both for reflections and refractions. You'll notice a bit more variation in reflection/refraction. In some cases increasing the max depth really helps to make your glass more realistic. It doesn't matter much here because our environment is also black, just like the exit color when max depth is reached. In colored environments the max depth effect will be more noticable. To continue, reset the max depth to 5.
14. Options: reflect on backside Go to the options rollout of the glass material, and turn on the 'reflect on backside' option. This will allow the inside of the surface to also reflect the environment. When rendering glass, you should leave this option turned on, it generates very nice and realistic inner reflections. This also increases rendertime of course... To continue the tutorial, turn it OFF again.
15. Glossiness The glossiness parameter is similar to the one for reflections. It's use is to blur the refractions. This is one of the most time consuming settings, rendertimes will go really high if you use high subdivs... Try a value of 0.8 with 8 subdivs. You'll see that the blurry refractions are very noisy due to the low subdivs. But you get the idea. Turn the glossiness back to 1.0
16. Index Of Refraction Set the IOR to 1.0 and render. The torus is gone! This is because no rays get bent with this IOR value. Because fresnell IOR is linked to the refraction IOR, this is also set to 1.0, which means the object becomes non reflective too. The refraction color is pure white, so the rays don't become tinted either! All this makes the torus dissappear.
17. IOR Unlink the fresnel IOR, so that its value is set to 1.6 again. Hit render. The thing you see now is purely created by reflections.
18. IOR Set the refraction IOR to 1.1 and render again. Each material has its own IOR value. Typical glass values are around 1.6. Do a google search for other common used material IOR's. Render a few tests with different IOR values. Reset the IOR to 1.6 to continue.
19. Exit color Like with reflection, there's also an exit color for refractions. After a ray has refracted the max depth number of times, this exit color will come in to play. tick the checkbox and give it a flashy green color. Hit render. You can clearly see what parts of the image go over the max depth number (5). Make the exit color black again.
20. Fog color The fog color is used to tint the refractions with a certain color. Thicker areas will become darker (more colored) than thinner areas. Try a light red color for fog and render. The material is very dark, but the thinner parts show some transparancy. The fog color and fog multiplier are actually an absortion control. The light looses its energy while traveling through the material. The longer it travels, the more energy will be absorbed by the object. That's why thinner parts will remain lighter than the thicker parts.
21. Fog multiplier Change the fog multiplier to 0.05 and render again. The fog effect is much weaker now, letting more light pass through, resulting in a lighter material. You should experiment with different fog color/multiplier ratios. For example a light but very saturated color with high multiplier, or a dark unsaturated color with a very low multiplier. You can get very different effects by playing with this relationship.
22. Refraction color You probably think, what's the use of the refraction color then?? Well, set fog options back to default, and choose a red refract color. Hit render. The glass is coloured too, but without the absorbtion effect. Thin and thik areas are equally coloured (the dark areas are refractions of the black environment!). I usually use pure white for refract color and play only with the fog options. But experiment with different refract color/fog settings to see what they do. Remember, dark refract color means less transparency. The saturation of the color has a huge impact on the look of the refraction. A very dark saturated color will look very similar to a very dark unsaturated color in the color swatch, but it will be completely different when used for refract color or fog color. Just try it!
23. IOR=1.0 mixed with fog Adjust refraction settings to the ones on the right. By mixing an IOR of 1.0 with fog color, you get a waxy kind of material.
24. Glossiness + IOR=1.0 + fog Adjust the glossiness to 0.75 and the subdivs to 16 and render again. The material looks a bit like reflective wax. Turn glossiness to 1.0 again and IOR to 1.6 before continuing.
25. Affect shadows An important option we didn't touch yet, it the affect shadows checkbox. It will have no effect in our test scene because there is no direct light, only GI light. The affect shadows options is only used with direct light rays. Therefore, we will replace the light box with a Vray Arealight. Go to the create panel and choose lights, and from the dropdown menu choose Vray.
25. Vraylight Click and drag in a viewport to create the Vray rectangular light. Make the size the same as our box, and position it in the same way. After that, hide the box. Set the Vraylight settings as in the image on the right (click to enlarge). The multiplier should be equal to the multiplier of the Vraylightmaterial you used on the lightbox. We now created a lightsource exactly the same as the lightbox, but it will cast raytraced area shadows.
26. Affect shadows In the glass material, turn ON affect shadows and hit render. The image should look like mine. As you can see, it casts green shadows. This is because the affect shadows option and fog color is used. Rendertime increases because the shadows are raytraced.
27. Affect shadows OFF Turn affect shadows OFF and render again. Notice the shadows are different now. This is because the GI caustics come back into play. This image is the physically correct one! When you have the affect shadow option turned ON, no refractive GI caustics are computed for that material, they are automatically turned off by Vray. The affect shadow option is nothing more than a 'fake caustics' option. So imagine that when using the affect shadow option, refractive caustics would not be turned off automatically, you would get a fake caustic effect AND a real GI caustic effect on top of each other! That's why Vray automatically turns off GI caustics for materials that have the affect shadow option turned on. THIS IS VERY IMPORTANT TO UNDERSTAND! Use the affect shadows option when you want light to pass trough refractive objects, and you don't want to enable refractive GI caustics, or when you don't use GI at all, or when you're using Max lights. Max lights will never produce refractive GI caustics! So if you want the light of max lights to pass trough refractive objects, you MUST use the affect shadow option. The second image on the right is rendered with an omni light as the only lightsource, and the affect shadows option is turned off. Notice the black shadows, no light passes through the material. The third image has affect shadows turned on. There is a fake caustic effect but it's nowhere near physically correct. Note that the Vray light is a special light. Although it casts direct light just like max lights do, they do produce GI caustics (max lights don't!). Normally only first bounce GI light (like the light coming from skylight and object lights like our lightbox) produces GI caustics. If you want real caustics when using max lights, you need to enable caustics in the caustics rollout (=photon mapped caustics). Don't do this right now, these caustics controls need a tutorial of their own... Just remember that you can get nice caustics effects by using GI and Vraylights much easier. That is why I prefer using the lightbox or Vraylight over the max lights. You simply check the GI caustics option and you don't have to care about other caustic settings all over the place! Drawback is that you need to have good GI settings for the caustics to be sharp, resulting in longer rendertimes. Another advantage of Vraylights or objectlights is that they reflect/refract in your objects. Max lights are invisible to camera and reflection/refraction. So to summarize: 1. If you use only object lights and Vraylights and you want caustics: - enable GI caustics - use good quality GI settings to make sure the caustics look sharp. 2. If you use max lights and you want the light to pass through refractive materials: - use the affect shadow option for a fake caustic effect - OR enable caustics in the caustics rollout and play with the settings for photon mapped caustics. 3. If you use Vraylights and you want photon mapped caustics: - Disable affect shadows - Disable GI caustics - Enable caustics in the caustics rollout and play with the settings.
28. Final material Use the material settings as in the image on the right. I lowered the fog multiplier a bit, and upped the max depth values both to 8.
29. Final image setup In the irradiance map settings, change everything as in the image on the right. Also go to the QMC sampler rollout and change noise threshold to 0.001 for maximum quality.
30. Final image Render the image, it should look something like mine. Notice the nice caustics and area shadows, controlled by the IR map settings. No caustics were enabled in hard to find places, no time consuming raytraced shadows were needed.
31. Comparison with QMC GI As a test, I rendered the image with QMC GI instead of irradiance map for first bounce. QMC GI is not an approximate method like IR map with its undersampling algorithm. QMC GI calculates the GI without compromise, every light sample gets equal attention. So it's a good test to compare how well the GI with IR map is computed. As you can see, in the areas with much lighting detail, the QMC GI image looks better (=more physically correct) than the IR map one. But it takes 10 minutes compared to 1m24s for the IR map version... If you want more detailed GI with IR map, you need to edit some of the IR map settings.
32. Better IR map settings This last image is rendered with optimized IR map settings. As you can see, this comes very close to the QMC GI example, but without any noise on the floor. I will explain how to optimize the IR map settings in an upcoming tutorial.
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