Opacity mapping is a great tool for material designers to understand. Similar to opacity maps are Masks. As I'm sure you've noticed just about any bitmap or procedural map can be applied to any map type. However, opacity maps aren't always the best way to achieve the results you want. Keeping that in mind let's look at what you can do with a mask and how its use is different than an opacity map.

On the first page I used refraction mapping to make a glass material. On the second page I used opacity maps to make dirty glass, and metal grates. All of these are fine examples of using transparency in materials.

Here is a variety of transparent materials achieved using transparency and refraction maps.

Now let's imagine that you just got asked to show off your MAX skills by doing a rendering of someone's product; a client has a logo and they want to see how it might look on merchandise, or painted on the plate glass windows of a new office. You are ready to go with the opacity maps and the glass. You have the logo scanned in, and you made an opacity map from it. You are ready to slap it all in place just like I applied the opacity maping to the factory windows! Or at least you think you are.

I scanned in the logo and then, using Photoshop, I made a black and white map for opacity. Now it's time to "paint" it on to a shot glass.

Space Happy Productions Inc. logo used with permision. © 2002 Tam Gambill

I want it to look just like it was silk screened on to the surface. Watch what happens when the maps are applied.

None of these examples using simple opacity maps produced acceptible results.

Using the logo and opacity map in the same way that I applied opacity maps to the grate and the dirty windows didn't work. In the first example above I didn't use any refraction mapping, and simply applied the black and white image as the Opacity map and the color image as the Diffuse Color map. The outcome is similar to the poor drinking glass on page 1. In the second example above I applied a Raytrace refraction map and set it to 100%. The logo is just barely visible on the glass although the opacity map casts a plain shadow. Then, in example three I turned the Refraction map down to 30%. The shadow is still crisp but the logo isn't. You may have also noticed that by using a stark black and white image for the opacity map in all three examples the glass is 100% transparent and therefore casts no shadow. It's not too convincing. Now let's go through the masking process.

In order to make the painted glass material for my shot glass I had to change my material type from Standard to Blend. You probablly already know or remember how to change your material type, but just in case here's the process.

Click the button, pick the type, and hit "OK"

A Blend material lets you select two different materials and mix them together into one. (If you feel like experimenting with Blend materials on your own creating a metal-flake paint is a good exercise). For the two materials in my Blend I used my glass material as the base material, and set up a masked material for my second.

Blend parameters are pretty simple to figre out. Once your two materials are selected you can adjust how they mix together using the mask, the spinner, or the mixing curve. By using a mix mask the spinner is deactivated.

Since I already demonstrated the creation of the glass material on page one I'll move on to the second material of my blend. On the left is the Maps roll-out for "Material #65 (Standard)". On the right is "Map #94 (Mask)" used for the Diffuse Color and Opacity maps.

 

A Mask functions like an opacity map within a map.If the diffuse color of your material is bright green and you apply a Mask to the Diffuse Color map slot you can then use your mask to cut out a part of the green and reveal another map beneath it.This doesn't affect the opacity of the material at all, only the opacity of the map within the slot it is assigned to. The map I used to mask my blend material was the simple black and white map that was applied as an opacity map in the three examples at the top of the page, and the map was the color scan of the logo.

The glass and the logo materials were selected as my Blend materials and the Mask I used to control the mix ammount was the opacity mask. The mask cut out a logo shaped space from the glass in order to let the logo colored material underneath show through. Now let's see if it worked.

(insert drum roll noises here)

Remember, you can get space happy without getting space hammered.

I'd say it was a success. The glass is there in all its refractive glory casting an appropriate shadow, and the logo is crisp and visible.

 

Masks can be applied to any of the map slots in the Maps roll-out. They can be used to layer textures in the Bump map slot, mask areas that should not be reflective in the Reflection map slot, map complex transparencies, and apply "paint" to Diffuse Color maps. For now I'll leave you alone to experiment with all this new information. In part 5 I'll tackle MAX's own material libraries. There are a lot of materials that come with the program; using what I've talked about so far I'll give you some tips on making the included materials even better. In the mean time keep creating, and feel free to E-mail me with any questions or comments.

Dxyner

 

 

pages 1 2

parts 1 2 3 4

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