Glass

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Glass

	GLASS MATERIAL To make a good glass you must know about a few things. Not only the material is important, but also geometry of your object and lighting. Your object which will have glass material must have its thickness, without it no glass will look natural. Usually you make glasses using one or more splines and lathe modifier. So when you prepare your splines make both sides of your object at once (look at picture below).
		Ok, object is ready. Now the lighting. Almost in all scenes you use more than one light source, and also for good glass you need a few lights. I usually use one strong spot light and 2 or 3 darker spots as fill lights. Also you can put one or more omni lights to make more speculars (glass material is highly specular). To do so go to omni properties and uncheck "Affect diffuse", leave only "Affect specular" on. Now use Place highlight tool to position your omnis so they produce speculars on proper areas of your object. Pictures below shows how I put my lights.
	And finally the material... Go to material editor and make material with parameters similar to those on picture below. I prefer metal shading for glass material, but blinn shading may work ok too. 2-sided material produce much more realistic glass so turn it on. Diffuse color should be rather dark, perfectly transparent glass should have black diffuse color, every change of this color will tint your glass. It is very important to keep opacity of your material at 100%. The most important part of your glass material is refraction map - use standard in MAX 2 raytrace texture. You may experiment with it's parameters to improve rendering time and quality. For rendering time the most important setting is trace depth - the higher value here, the longer rendering time, but if you reduce it too much render quality will be very poor (black areas on parts of rendered picture may appear). Use 60-95% amount of raytrace map - depending on how transparent your glass should be. One more important setting is in extended parameters: RayTrace IOR - this is index of refraction - this defines how much light refracts when going thru glass. Common glass IORs are from 1.6 to about 2.
		Now you can make a test render to check how good your glass is. For test renders you may want to turn off antialiasing to speed up rendering. Test render should look similar to this one: You see lots of pixels with different colors that look terrible. This is because there is no antialiasing on edges and surface of the glass. If you turn on antialiasing in rendering preferences to improve edges quality. And to improve glass surface quality turn on Supersample in basic material parameters. But remember that both antialiasing and supersample increase rendering time very much.
	And yet a few words about glass: some areas of rendering look too clear. Glass is highly refractive, but also reflective material. You can apply raytrace texture for reflection map, but combining raytrace map for both reflection and refraction is a killing combo for any CPU :) So you can fake some reflections using bitmap with environment/spherical mapping. Use some landscape texture preferably with dark colors for best reflections. Amount of those reflections you must find yourself because it is different for every material and bitmap
		(click to enlarge)