Realistic renders in 3DS Max
Super powerful computers allow us to push the limits of our imagination and we want to bring our ideas to life using 2D softwares and 3D softwares.
So, what defines a realistic render? A good modeling of the objects? Good lighting? Everything in a perfect order? Overall render settings? A simple formula could be: Realistic render=(modeling, texturing, lighting, render settings) + (details from the real life)
A realistic object or scene rely on its level of detail. Also a perfect order it's not always real. A chair which is not parallel with the table, a cup of coffee on a corner of the table, an unordered stack of books or overall asymmetry gives the feeling of "real" in a scene. If the properties of the objects, like the shape and details, color, texture or the level of reflection/refraction are almost the same as the real one and the overall illumination it is properly done, then the scene became "realistic".
A common mistake is not giving enough attention to small details like edges. In real life the edge between two surfaces at 90 degrees it's not sharp in 99.9% of cases. Imagine two small wood cabinets one on top of each other, modeled without chamfer of bevel their edges. Nobody will see where one of them ends and the other begins.
Modeling with real proportions will give you more control on objects as long as the scene begins to populate and for the overall render settings.
Materials and textures
A good texture or a carefully made material will bring "realism" in your scene. Choose only highly detailed textures, tileable ones if possible or needed. If you don't know how to make a material like a car paint or silk, look after a tutorial and your scene will be alive.
If you have an object like a wood table, don't apply a wood texture on the entire object. Take a little time and apply the texture on every element of the table and carefully apply UVW Mapping so that the wood fibers looks real.
Be careful about the reflection and refraction of the materials, the level of glossiness and the subdivisions. Reflection also emphasize the edges. Keep in mind that the lower the glossiness value, the higher the subdivisions should be. Use correct values of IOR for transparent materials (you can take them from this link)
Take time to modify the texture on every element, so they don't look the same. Rearrange the texture for a little diversity and realism.
Bump and Displacement
Try to apply bump or even displacement maps to textures, or else all objects in the scene will look like shiny (more or less) plastic. Displacement consume more of your system resources, so use it wisely on the objects that are in front of the camera for a maximum realism.
In real life every object radiates light, more or less. In 3D software, if we render a white cube on a white surface, the result will not be satisfying at all. The ambient occlusion helps render our cube like it appears in an overcast day, emphasizing the details.
This type of reflection appear when you are looking at the sea and at your feet you have almost no reflection, but if you look further the water is getting more reflective. The same is with a road which is reflecting like a mirror close to the horizon. Materials like porcelain or shiny marble has this effect. Explore some examples at this link.
If the objects and the overall scene was carefully modeled and textured, the next step is the light. If is not properly calculated and the light came from unnatural sources, then everything could be lost. Use photometric lights and HDR for environment. If the HDR file has a light source in it, then try to match the position of your light source (like the sun) with the light from the HDR file.
Rendering I will take the example of rendering with V-Ray engine. For a better control of the final render, it is wise to use V-Ray Frame Buffer and render elements and then compose them in Adobe Photoshop.
In this way you can have more control for every layer that compose your final scene. So keep in mind to add (at least) the following Render Elements: diffuse, Vray lighting, Vray reflection, Vray shadow, Vray specular and, in some cases, Vray ZDepth. A well known rule is to give attention to samples values for material subdivisions, image sampler, brute force or light cache, Vray DMC sampler. Also you it is indicate to work with a 2.2 Gamma. See the differences at this link.
The key is to keep learning!