
9	Surface Textures
	Surface textures are two-dimensional textures that simulate various types of surface materials by using either an image file (*File* and *Stencil* textures) or a computer graphic procedure (*Bulge, Checker, Cloth, Curvature, Fractal, Grid, Highlight, Mountain, Noise, Ramp, and Water* textures). In This Section: Using Surface Textures 128 Texture Placement Window 137 Surface Texture Parameters 146 Surface Texture Types 149 File Texture 151 Bulge Texture 155 Checker Texture 156 Cloth Texture 157 Fractal Texture 160 Grid Texture 162 Mountain Texture 164 Noise Texture 167 Ramp Texture 168 Stencil Texture 174 Water Texture 177 Using Surface Textures

	You can use surface textures to simulate two-dimensional materials (for example, cloth). The *File* and *Stencil* textures are used to specify an image file. The *Curvature* texture is used by the *Surf curvature* and *Surf curv params* tools. The *Highlight* texture is used by the *Highlight* and *Highlight params* tools. Reducing Surface Texture Distortion By default, surface textures are mapped to a surface's parametric space. That is, the XY values of the texture are mapped to the UV parameters of the surface. If the surface's UV parameterization is non-uniform (that is, the U and V isoparms are not uniformly spaced), then the texture will appear distorted. This often occurs when mapping a surface texture to a curved surface. The greater the surface curvature, the less uniform the parameterization, and the greater the texture distortion. If a surface texture appears distorted on a surface, do one of the following:
See Rebuilding Complex Surfaces in the Modeling in Alias book.	Make sure your surface is evenly parameterized. You can use *Rebuild Surface* to re-create the surface with uniform parameterization.
See Chord Length on page 147.	Use chord length mapping by setting *Chord Length* ON.
See Projection Texture on page 191.	Use the surface texture as a source texture for a *Projection* solid texture.
See Worldspace on page 147.	Use world space mapping by setting *Worldspace* ON. Label Mapping Label mapping is a technique of applying an image file onto a surface (for example, a label on a shampoo bottle) and masking parts of the image file so that it covers only a portion of the surface. The *Stencil* surface texture is used for both mapping and masking. *To map a label to a shader:* 1 In the shader's *Control Window, click the Map* button to the right of the *Color* parameter. The *Texture Procedures* window appears. If you are planning to mask the label, continue with step 2. If you do not need to mask the label, you can skip to step 4.
	2 In the *Texture Procedures* window, click the *Stencil* button. The *Texture Procedures* window automatically closes, a *Stencil* texture swatch appears in the *Multi-lister, and the Control Window* displays the texture's parameters. 3 In the *Stencil* texture's *Control Window, click the Map* button beside the *Image* field. The *Texture Procedures* window appears.
	4 In the *Texture Procedures* window, click the *File* button. The *Texture Procedures* window automatically closes, a *File* texture swatch appears in the *Multi-lister, and the Control Window* displays the texture's parameters. 5 In the *Control Window, type the name of the image file you want to use as the label in the Image* field, or click the *Browse* button and select the image file using the *File Requestor. The image file is now mapped onto the shader, and appears on the shader swatch in the Multi-lister. By default, the image file covers the entire shader. However, you can limit the area it covers by masking the label and/or positioning it on the shader. Label Masking A mask controls the transparency of a Stencil* texture and limits the area on a surface where the texture will be visible. There are two types of masks: file masks and chroma key masks. File Masking File masking uses a texture or image file to specify which areas of the *Stencil* texture are transparent. Where the *Mask* file is white, the *Image* file will be visible on the surface. Where the *Mask* file is black, the shader color will be visible on the surface. Where the *Mask* file is grey, both the *Image* file and the shader color will be partially visible. If the *Image* file has four channels (RGBA), then you can use the same file for both the *Image* file and the *Mask* file. The RGB information will be used for the image portion of the stencil and the A (alpha) will be used for the mask portion of the stencil. If, however, the *Image* file has only three channels (RGB), then you must create a separate *Mask* file. You can create a *Mask* file by converting the *Image* file to black and white using a paint program (for example, VizPaint2D or StudioPaint). Although you can use a color image file as a *Mask* (for example, you could use the same file for both the *Image* and *Mask), the level of transparency of the mask will vary through the range of colors. To mask a label using an image file mask:* 1 In the *Stencil* texture *Control Window, click the Map* button beside the *Mask* parameter. The *Texture Procedures* window appears.
	2 In the *Texture Procedures* window, click the *File* button. The *Texture Procedures* window automatically closes, a *File* texture swatch appears in the *Multi-lister, and the Control Window* displays the texture's parameters. 3 In the *Control Window, type the name of the image file you want to use as the mask in the Mask* field, or click the *Browse* button and select the mask file using the *File Requestor. The Mask* is now mapped onto the shader, and the *Image* file no longer covers the entire shader swatch in the *Multi- lister. The Mask* file is automatically positioned in the same location as the *Image* file. To control the overall transparency of the *Stencil* texture, adjust the *Rgbmult* value in the *Mask* file's *Control Window. To control the softness of the mask, adjust the Bluroffset* value in the *Mask* file's *Control Window. Small values (around 0.01) are most useful. Chroma Key Masking Chroma key masking does not require a mask file. Instead, you set the Stencil* texture's *HSV Color Key* parameters so that a certain color, or a certain range of colors, are either visible or invisible. Chroma key masking has no effect if an image file is mapped to *Mask. Make sure there is no Mask* file assigned to the *Stencil* texture (type a space in the *Mask* field) if you want to use chroma key masking. *To mask a label using chroma key masking:* 1 In the *Stencil* texture *Control Window, click on HSV Color Key* to display the *HSV Color Key* parameters. 2 Set *Key Masking* ON. 3 Click the color field beside *Color Key* to open the *Color Editor. 4 Click the Grab* button in the *Color Editor. The mouse pointer becomes an eye dropper. 5 Move the eye dropper over the Multi-lister, and click the left mouse button on the background color of the Image* texture. All areas of the *Image* texture that have this color are now transparent (masked) and the shader color is visible in these areas. To mask a range of colors, adjust the *Hue Range, Sat Range, Val Range, and Threshold* settings. To invert the mask, set *Positive Key* ON. Only the color (or range of colors) specified in the *HSV Color Key* parameters are visible, instead of masked. When you are finished masking the label, click the arrow in the bottom right corner of the shader swatch to hide the *Stencil* texture and the *Image* file (and the *Mask* file if there is one). To preview the label map and mask, use *Quick render. You may want to open the Global Quick Rendering Parameters* window and increase the *Shading Frequency* value to better visualize the label map and mask. However, if you have to increase the *Shading Frequency* value to 10, it may be faster to do a full render. To position the texture on a surface, see Positioning Surface Textures below. Positioning Surface Textures By default, a texture mapped to a surface covers the entire surface. You can mask the texture so that it is only visible in certain areas of the surface. You can also scale and/or position the texture so that it covers only a certain area of the surface.
See Surface Placement on page 146 and Label Mapping on page 148.	Two sets of parameters control the positioning of the texture: the *Surface Placement* parameters and the *Label Mapping* parameters. If you adjust these parameters in the texture's *Control Window, the shader swatch in the Multi-lister* will update to reflect any changes you make. Therefore, by editing these parameters directly and using the *Multi-lister* as a preview, you can roughly position a texture on a surface. There are, however, two easier methods of positioning a texture on a surface: 2D mapping and 3D mapping.
	Each surface texture swatch in the *Multi-lister* has two small icons in its bottom right corner. Clicking on either of these icons activates the corresponding method of texture placement. It is also possible to use 2D mapping and 3D mapping simultaneously. For example, you could use 3D mapping to visualize the texture on the surface and use 2D mapping (the *Texture Placement* window) to position the texture. 3D Mapping The 3D mapping technique displays the texture directly on the wire frame of the surface to which the texture mapped shader is assigned. This display is updated each time you adjust any of the *Surface Placement* or *Label Mapping* parameters. *To use 3D mapping to position a texture on a surface:*
	1 Make sure that the texture mapped shader is assigned to the appropriate surface, and that this surface is the only active object in the modeling window. 2 Open the texture's *Control Window, and open the Surface Placement* and *Label Mapping* sections. 3 Click the 3D mapping icon in the bottom right corner of the texture swatch in the *Multi-lister*.
	The modeling window displays the texture directly on the wire frame of the surface. 4 If necessary, increase the patch precision of the surface to better visualize the texture. Patch precision represents the number of curves (visual isoparms) that are displayed to represent each patch on a surface. On most surfaces, the default patch precision of 2 is too low for 3D mapping. Increasing the patch precision, however, will also increase the screen refresh time.
	Select *Object > Patch precision* and enter a number between 2 and 30. The number of visual isoparms per patch increases, making the texture pattern more visible.
	5 You may want to use *Shade* display mode to better visualize the texture. Select *DisplayTgls > Shade. The surface is displayed in shaded mode. 6 Adjust the Surface Placement* and *Label Mapping* parameters until the texture is correctly positioned on the surface. The *Label Mapping* parameters control the position and orientation of the texture relative to the surface (see Label Mapping on page 148). The *Surface Placement* parameters control the position and orientation of the texture pattern relative to the texture (Surface Placement on page 146). 7 Click the 3D mapping icon in the bottom right corner of the texture swatch in the *Multi-lister. The modeling window no longer displays the texture directly on the wire frame of the surface. 8 If you turned on the Shade* display mode in step 5, select *DisplayTgls > Shade* to turn it off. 9 If you increased the patch precision of the surface in step 4, reset the patch precision of the surface to its default value (2). *Select Object Edit > Patch precision* and enter 2. 2D Mapping The 2D mapping technique uses the *Texture Placement* window to display and position a texture. The horizontal and vertical dimensions of this window (S and T) represent the two parametric dimensions of the active surface (U and V). A texture mapped to the active surface will therefore be displayed in the *Texture Placement* window relative to the surface. The buttons at the bottom of the *Texture Placement* window allow you to interactively edit the position and orientation of the texture relative to the surface. The 2D mapping technique is slightly different when you are positioning a texture on a spline surface and when you are positioning a texture on a face. This is because the range of the U and V parameters is different for spline surfaces and faces. The range of the U and V parameters of a spline surface is always 0 to 1. The range of the U and V parameters of a face is based on the size and location of the face when it is created. *To use 2D mapping to position a texture on a surface:* 1 Make sure that the texture mapped shader is assigned to the appropriate surface, and that this surface is the only active object in the modeling window. 2 Click the 2D mapping icon in the bottom right corner of the texture swatch in the *Multi-lister*.
See Texture Placement Window on page 137.	The *Texture Placement* window opens and displays the texture relative to the active surface.
See Xform Menu on page 143.	3 Use the *Xform* tools in the *Texture Placement* window to position and orient the texture relative to the surface. The texture's *Surface Placement* and *Label Mapping* parameters are automatically updated when you use the *Xform* tools. 4 Close the *Texture Placement* window, either by clicking the 2D mapping icon in the texture swatch in the *Multi-lister, or by clicking the close box in the top left corner of the Texture Placement* window. *To use 2D mapping to position a texture on a face:* 1 Make sure that the texture mapped shader is assigned to the appropriate surface, and that this surface is the only active object in the modeling window. 2 Click the 2D mapping icon in the bottom right corner of the texture swatch in the *Multi-lister. The following confirm box is displayed: If you select YES, the texture map is automatically scaled to fit the face. If you select NO, the texture is not scaled and the following confirm box is displayed: If you select YES, the view automatically dollies out to fit the selected faces into the Texture Placement* window. If you select NO, the view remains in the worldspace origin. If you select YES to both of the above prompts, the texture will be scaled to best fit the selected face. The *Texture Placement* window opens and displays the texture relative to the active surface.
See Xform Menu on page 143.	3 Use the *Xform* tools in the *Texture Placement* window to position and orient the texture relative to the surface. The texture's *Surface Placement* and *Label Mapping* parameters are automatically updated when you use the *Xform* tools. 4 Close the *Texture Placement* window, either by clicking the 2D mapping icon in the texture swatch in the *Multi-lister, or by clicking the close box in the top left corner of the Texture Placement* window.