MAPPING MATERIALS

Whenever you are attaching materials to an object in AutoCAD, you are effectively ‘stretching' the image of the material around the object. For many objects, this can be acceptable. For a lot of others, though, you may want to adjust how the material is displayed on the object. This process is called mapping.

Here is an example of the same object with the same material, but with the mapping of the material adjusted (cylindrical) on the right-side object.

By default, AutoCAD will apply the material as it sees fit. If you were adding the material to a floor tile this would be ok. But if you were adding material to a marble column, the right side object may more realistic. This lesson will explain some of the basic concepts involved with this.

The command to start this is ‘SETUV', or you can use this icon. With a little knowledge of this command, you can make your renderings more realistic.

Begin by making some primitive objects on your screen. Create a Cylinder, Sphere and Box. See the lesson on Primitives to review if you need to.

First we'll look at the cylindrical object shown in the example above. Pick a material and apply it to your cylinder. I suggest using Marble-Tan or some other material with a good, clear, varied texture. Once the material is applied, copy it to one side and render the scene. Make sure that you have your render type set to either Photo-Real or Photo-Raytrace. The two objects should like the one on the left in the previous example.

Now start the SETUV command. Your command line will prompt you to select an object. Pick one of your cylinders and press enter. This dialog box will appear:

Change the top radio button from Planar to Cylindrical. Press OK and re-render the scene. You should see results similar to the example at the beginning of the lesson.

Use the same procedure to apply Spherical mapping to your sphere object. The objects will look similar, but you should see that the ‘non-mapped' object has the material mirrored across the midway point. The mapped object has a smoother appearance to its material. See the example below.

This example shows a sphere before (left) and after (right) adding spherical mapping.

In this example, you will create a small ‘floor' and apply the marble material to it. Create a 10'x10' rectangle and then extrude it ½". Apply your material to it and then render the scene. What you get is one BIG piece of marble that doesn't really give the effect you want:

Above is a 10'x 10' slab of marble as rendered by AutoCAD

The next step is to make the floor look as if it is constructed of 12x12 marble tiles. To do this, first draw a 12x12 rectangle on one corner of the floor. (This will be your reference for mapping). Now start the SETUV command, select your object and choose the Planar option. Pick on the Picked Plane button and select 3 corners of the 12x12 rectangle. Have a look at the dialog box and notice the small blue square on the corner of the red square representing your floor. This is the scale of the mapping.

Render the scene and you should see a difference.

You now have a floor made up of 12x12 tiles. This is still not perfect, as all the tiles are identical and placed in the same orientation. This is just a quick example of mapping. To get a even better result, you would have to create individual tiles, allow for grouting between them and then rotate some of them to break up the pattern. This method is used for items such as brick walls and roofing tiles. Depending on the amount of time you have and the detail required, it can get very involved.

The last option we'll cover here is the ‘Adjust Bitmap' option. This is on the ‘Adjust Planar Coordinates' dialog box. Choosing this option gives you control over the scale of the image file that makes up the material. Move the slider bars to adjust the bitmap to stretch it either vertically, horizontally, or just scale the image down in size.

This adjustment will give you a 'stretched tile' as shown in the image below. You want to make sure you know what you're doing when you do this.

Remember that you only adjusted the bitmap for the objects you selected. The base material has not changed.

Practice with the SETUV command on basic objects and you will soon have better looking renderings. This is one more step in getting realistic looking materials.