Note that by default Brute Force has 3 light bounces and Light Cache works with light bounces. All the examples are set to their default values.
Quick Search. V-Ray 5 for 3ds Max. A t tachments 8 Unused Attachments Page History. Page Information Resolved comments Link to this Page?? Pages Rendering Concepts. JIRA links. Skip to end of metadata. Page Contents. Overview Indirect illumination refers to illumination that results from the bounced light in a scene, as opposed to illumination directly from light sources. The following types of indirect illumination engines are supported in V-Ray for 3ds Max. Brute Force GI - The simplest approach where indirect illumination is computed individually for each shaded surface point.
Final Gather Rollout mental ray Renderer. Indirect Illumination Panel. Command entry: Render Setup dialog Indirect Illumination panel Note The Indirect Illumination panel appears only when mental ray is the active renderer. These controls are on the mental ray panel of the Object Properties dialog. Automatically Calculate Energy and Photons When on, the light uses the global light settings for indirect illumination, rather than local settings.
Global Multipliers group Energy Multiplies the global Energy value to increase or decrease the energy of this particular light. Caustic Photons Multiplies the global Caustic Photons value to increase or decrease the count of photons used to generate caustics by this particular light. In turn, these are already reflected rays, striking the other surfaces, in the same way, each again forms a set of rays, and so on and on.
Global illumination ray can bounce many times, depending on the number of bounces, defined by the parameters of the renderer. Based on the image above, it is easy to imagine that they form a hemisphere, similar to a half of dandelion inflorescence. Vectors of the rays diverge in all degrees in different directions, by the hemisphere from the point of reflection.
That is how the rays behave in the GI engine, and because of the shape of the reflection, they are called Hemispheric Rays. It should be noted that bounces of light rays of the global illumination in V-Ray is divided into Primary bounces first reflection , and Secondary bounces all subsequent ones. The first ray bounce from the object scene called the Primary bounce not without reason. The whole point is that the rendering engine that simulates the behavior of the real world sets the fading of the rays as they reflect.
Therefore, as happens in the real world, the first bounce bears much of the reflected light energy. The energy of this first primary bounce is so significant that it much more than the light energy of all subsequent reflections together.
It one affects the illumination of the scene greater than all subsequent ones. Conversely, in view of their lesser importance, all the bounces that follow the first primary one, called the secondary bounces.
Open the Render Scene dialog F10 key and go to the Indirect illumination tab. It controls global illumination, rendering algorithms, the choice of primary and secondary bounces engines and general settings of GI. This rollout has On checked and divided into four zones: GI caustics , Post-processing and two similar zones, Primary bounces and Secondary bounces. They contain the following parameters: Reflective , Refractive , Saturation: , Contrast: , Contrast base: , Multiplier s and GI engine: s drop-down lists.
First, to enable global illumination in a scene we should set tick in the checkbox named On. After this, we have available parameters of the V-Ray global illumination engine. In short, caustic is the place where the reflected or refracted rays from the reflective and transparent curved surfaces are gathered, drawing a specific clearly visible light patterns.
In other words, this is the effect of the curved lens, projecting the light rays on some surface, where the lenses are the reflective and transparent objects of the scene. The most obvious example of caustic is fancy light pattern on the table near the glass, on which the light shine from a side.
It is these effects simulates caustics photon map, situated in the V-Ray:: Caustics rollout. Despite the fact that current rollout is the last in the Indirect illumination tab and logical to write about it as the very last thing we would like to briefly write about it right now.
The calculation of caustics in the V-Ray is accompanied by the appearance of a large number of artifacts, excessive consumption of memory and complex pre-configuration. All this is for the minimally noticeable, and often absent effect in most scenes.
In the universal starting V-Ray configuration, rendering caustics should not be enabled. However, it should be understood that the calculation of caustics and GI caustics are two different things. Caustics, created by the aforementioned photon map can be calculated only for direct rays of light. While GI caustics are calculated separately.
The GI caustics configuration area in the V-Ray:: Indirect illumination GI rollout are responsible exactly for these caustics, which are originated from the global illumination. Moreover, GI caustics are called caustics only by a certain analogy with photon caustics, in fact, they are not. Option Reflective allows us to enable rendering of reflective GI caustics for GI bounces, allowing GI-rays to take into account the reflective properties of materials and better reflect from reflective objects such as chrome, mirrors and other.
Given the lower energy of indirect bounced rays, compared with the rays from sources of direct light, the effect of reflective caustics on the overall scene illumination is negligible. In addition, since the need to render Reflective caustics by renderer, their inclusion will increase the render time of global illumination.
Moreover, taking into account the complexity of this effect sampling , the appearing of unwanted noise in the GI is possible. Considering mentioned drawbacks, this option should be nominally left off in the universal starting V-Ray configuration. Refractive option allows us to include rendering of refractive GI caustics for GI bounces.
Despite the similar name to the caustic from the direct rays of light sources, where it simulated caustic lighting effects, Refractive caustics simply allows the passage of secondary illumination through the transparent surface.
Lack of calculation of Refractive caustics in the scene will render all black, simply because the GI rays will not fall into the interior, because they not are able to pass even through the transparent glass window. For most scenes, such behavior is unacceptable and therefore GI option Refractive in universal V-Ray settings should be activated by selecting the checkbox Refractive.
Saturation is a very important parameter of GI, which is responsible for the color saturation of reflected light or, as practice shows, simply for the value of the so-called color bleeding effect. Rendering of the slightly modified example scene. All left unchanged but the material of the central cube. It is red now. Image represents the effect of color bleeding, which leads to lighting the all scene in the color of the inside objects.
The scene is colored red because of the presence red cube in it. This image is a rendering of used earlier scene, with the same light source, with the same material objects, with one exception, the material of the cube is red. There is no need much time to look closely to the image, comparing it with previous ones to realize that not only the cube, but other scene objects got a reddish tinge.
This effect is quite common for the real world, and actually is the phenomenon of color bleeding. Its nature is quite simple. Red object is an object that absorbs the rays of all colors and reflects only the red color rays. It is this effect clearly imitated on this image. Direct rays of white color, which, as we know, bears all the colors of the visible spectrum, falling from a window on the surface of the cube, and then reflected.
But they no longer reflected white, as they were originally. They are reflected red, as red material of a cube absorbed all the colors except red. Thus, the red cube lights nearby objects and paints them red. Lowering a Saturation: value, will help to get rid of this effect. A lower value makes the color saturation of diffuse reflection paler, while the larger value makes it richer. That is the same scene with the same red cube, but with a value of Saturation: , equal to zero:.
Rendering of the example scene with the red-colored cube inside it. The parameters of the rendering set so the Saturation: of the GI lighting set to zero. This means the diffuse GI reflection do not have any color contrast. Image shows there is no color bleeding effect at all even with the big red cube inside the room. This image is no longer has red walls, but it should be understood that this is a global setting that affects every diffuse reflectance in the scene, reducing the color saturation of all GI rays.
In most cases, a strong understating or overstating of this parameter gives an unnatural result. Optimal for the vast majority of the scenes is the value of this parameter equal to 0. That it must be set in the universal starting V-Ray configuration. If there is a need to correct the effect of color bleeding of any particular object or material, for local control of this aspect the VRayOverrideMtl should be used.
Contrast: and Contrast base: are the parameters that literally control the contrast of GI, which renderer uses in forming of the final image, similar to how Saturation is essentially just controls color saturation of GI.
Contrast: parameter works in conjunction with the Contrast base:. Technically Contrast base is one of the variables of the algorithm that computes the contrast of GI render element, shifting the range of its values, thereby affecting its brightness.
When Contrast base is zero, increasing the value of the Contrast: parameter brightens GI; at the Contrast base greater than zero, the overall brightness is increasing, and increasing of the Contrast parameter value leads to darkening of GI. In the vast majority of cases, there is no need to somehow change the contrast of the GI. Therefore, in starting V-Ray settings, their value should not be changed, leaving 1 for Contrast: and 0,5 for Contrast base: , as it is set by default.
The number of GI settings causes panic to many 3d visualization artists. In fact, in these settings everything is fairly logical. There are primary and secondary bounces of the ray. Both are computed with special GI engine algorithms. There are four GI rendering algorithms in V-Ray.
Their choice can be compared with choosing of antialiasing algorithms.
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