The candleholders above look pretty good, good enough that you could probably tell they were brass without having to be told. Still, they are lacking something; if you look at the marble you'll see it. Reflections are an essential visual cue. The marble slab on the left could be a marble printed cardboard box. The slab on the left is unmistakably polished stone. It is reflecting the object on top of it. What keeps most people from walking smack into a closed glass door? Both air and glass are transparent materials, but the glass has reflections that let us know there is something there we can't walk through. MAX offers reflection maps to help users add that element of reality to their materials.

Let's take a look at our candleholders again.

In this example all of the specular settings on the marble and the brass are identical. The differences between the objects on the left and right (and from the example on page 1) are in the reflection maps applied to the materials. To access the Reflection maps menu open the maps rollout (just like you did to set up bump maps from part 2).

Now scroll down to the Reflection map options.

There are several options for reflection maps. When you click on the bar to the right of the spinner window the Material/Map Browser will open. Any of the maps listed there can be used as reflection maps, however there are a few designed specifically for that purpose. In this tutorial the only ones I will address are Raytrace and Bitmap.

 

Raytracing is a mathematical process that rendering programs use to calculate reflections, refraction, and shadows. It's a powerful tool, and most good rendering programs have some form of raytracing built into them. In the natural world light reflects off surfaces at a direction equal to the direction it intersects them at. These directions are known respectively as the angle of reflection and the angle of incidence. Raytracing calculates angle of incidence for each face of a MAX object and then calculates the angle of reflection (or obstruction in the case of shadows). Materials mapped with raytraced reflections act as mirrors.

The angle that the light beam is reflected off of the surface is always equal to the angle at which the light intersects the object. In this illustration you can see that the angle of reflection into the surface is also equal to the angle of incidence.

In the illustration of the candleholders at the top of this page the stone surfaces as well as the candleholder on the left have raytraced reflection maps applied to them. Once the type of map has been selected for your reflection you can set the strength of that map. Like setting the strength of the bump maps in part 2 the strength of the reflection map is controlled in the spinner window to the right of the on/off check box. The strength of the reflection applied to the marble surface on the left is higher than the strength of the map on right-hand piece. The reflection is clearer on the left as more of the light rays intersecting the surface are reflected off of it.

In the candleholder on the left a raytraced reflection gives a very shiny look with a lot of detail. The raytracing reflects the candleholder on the right onto the candleholder on the left. The reflections in the surface of the left-hand candleholder are also re-reflected into facing surfaces. If you click on the thumbnail image you can see an clearer example of how complex and detailed raytrace reflections are. They are also time consuming to render. If you were to fill an entire scene with raytraced materials it would take hours on most personal computers to render a single frame. The full size rendering of these spheres took my underpowered machine almost 5 minutes to render completely. Luckily there are other types of reflection maps that can be applied to materials.

 

In the candleholder illustration at the top of this page the candleholder on the right still looks like a suitably shiny brass. It certainly looks less cluttered; it even seems to have the sort of falloff that brushed metal or lathed objects have in the natural world. In this case the reflection map is a bitmap image that has been modified. Selecting a bitmap for reflections is the same as selecting a bitmap for the bump map. Click on the bar next to the spinner window, and when the Materials/Maps Browser opens select Bitmap from the top of the list. For the candleholder I chose a reflection map from the MAX ref_maps folder.

The bitmap selection window should look familiar.

The map settings window will open after you have selected the map you want to apply.

By blurring the map before applying it as a reflection the original image is not identifiable as a lake reflected on the candleholder. As with any other map the strength can be adjusted in the Maps rollout. For the brass material I set the reflection map strength lower to allow more of the diffuse map to show through. There are instances where it may be appropriate to leave the reflected bitmap unblurred. If for example you have an object in your scene that should reflect something other than the background image a bitmap reflection map would one way to achieve that.

To avoid getting a reflection of the same trees and fence in the top half of the Alien Sphere I applied a bitmap reflection of what scenery I wanted outside the field of view without having to build new geometry.

 

There are a lot of ways to use the diffuse and reflection maps; I have only showed the most basic details here. The MAX help files in the Online Reference are very helpful in understanding what various maps are for and how to use them. I encourage everyone who is using this tutorial series to also make frequent visits to the Online Reference. And of course the most usefull learning tool, experimentation.

Thanks to all of you for being patient in waitng for this third part. I will try to get part 4 online soon. In the meantime keep practicing what you have learned so far, and feel free to e-mail me with any comments or examples of what you have accomplished.

Dxyner

 

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This tutorial, all text and images contained herein, and all banners and logos are (c) Flaming Ball -o- Death Designs 2002