V-Ray is a very popular visualizer with the widest set of features. A variety of different render settings in V-Ray 3DS Max allows you to create realistic scenes of any complexity.
Good thoughtful modeling is the basis for rapid calculation in V-Ray. Analyze and, if necessary, correct the geometry of the scene, for example, without gaps, a joint of surfaces must be made, long thin polygons are excluded for use. Each model in the scene is better represented as a separate object. Be sure to consider that the ratio of the sizes of objects in the scene should be similar to the ratio of the sizes of real objects.
This is important in the calculation of Global Illumination and affects the level of photorealism of the created scene.
In V-Ray, the parameters of image sampler and GI engine influence the quality of rendering and speed most of all. Correct setting of these functions allows to significantly improve image quality.
V-Ray image sampler calculates the pixel color based on the colors inside and around it, sampling the images.
Since each pixel in an image can only have one specific color when rendered, V-Ray calculates it based on the material of the object and the direct light that hits the object, taking into account the indirect lighting in the scene.
After all, even within a single pixel, there can be a superposition of several colors emanating from neighboring objects whose edges intersect in this pixel, or one must take into account differences in brightness on the same object due to its shape and shading of light sources.
V-Ray offers two main image samplers, each of which has its own approach to sampling and its own parameters: Progressive and Bucket, and the correct setting of GI parameters (Irradiance map, Photon map, Brute force or Light Cache) will achieve the desired effect from the illumination in the scene.