
	Texture Maps

There are two ways to surface a polymesh; dense patches that fit very closely, or light patches that are texture mapped.

Figure 108. Light Weight Patch

In the first approach you would start by building light patches, getting the flow how you want, and matching the boundaries (see Figure 108).

Figure 109. Successive Doublings

Then to make the patches denser, keep doubling the divisions; the patches will end up fitting closer and closer to the underlying polymesh. In the extreme, the number of CV's in the patches will approach the number of points in the polymesh (see Figure 109). The error between the patches and the polymesh will be almost zero at this extreme density. Obviously, the price for this fitting accuracy is a very complex and unwieldy NURBS surface.

Figure 110. Error Between Patch and Polymesh

In the second approach, building light patches is also the first step. But then the error between the simple patches and the polymesh is calculated and saved as gray scale images (see Figure 110). These images, called displacement maps, can then be applied to the simple patches during rendering, and all the detail of the original polymesh is retained.

Figure 111. Light Weight Patch - Texture Mapped

Figure 111 shows an example of displacement mapping. The image on the left is the simple patch rendered with the displacement map shown on the right. The patch captures the shape of the surface, and the fine detail is stored very efficiently in the image file.

Load The Maximum Detail Polymesh

As mentioned in the "Loading Meshes" chapter above, it is a good idea to build your networks on decimated (i.e. polygon reduced) meshes; placing points, drawing curves and fitting patches will be much quicker.

But when you come to calculating texture maps, you want to do that off the maximum detailed polymesh. So, before continuing with the texture mapping process, save your network into a SLICE file, load the original detailed polymesh, then load the SLICE file you just saved.

Texture Map Parameters

If you want to calculate texture maps, then you'll need to define the following four values for each patch:

Name. Used to name the texture map file.

Size. The X and Y pixel dimensions for the texture map image.

Type. Whether to calculate displacement, or color, or both.

Error. The error envelope for that patch.

Figure 112. Texture Map Controls

For those with lots of patience, the Texture Maps panel lets you set these values by hand, one patch at a time (see Figure 112). But for the impatient, there are also ways to quickly set values for all patches.

Picking Patches

Before you can set the values for a patch, you have to pick it. There are two ways:

(1)

You can select patches one at a time from the 3D display. First click on the Pick button, found towards the top of the Texture Maps panel, to put CySlice in patch picking mode. Then click the left mouse button on a patch's seed point to pick it. The selected patch will then be drawn in yellow, and its values for the four parameters will be loaded into the Texture Maps panel. You can then change a value, and when you pick the next patch, that value will be stored.

(2)

You can cycle through patches in the order that they were first created. Click on the left or right blue arrows, found near the Pick button, to pick the next or previous patch. As with the previous picking method, the selected patch will be drawn in yellow, and its values will be loaded.