Mapping Textures

Motivation

You can model every tiny texture detail of a world using a vast number of colored faces:

• Takes a long time to write the X3D
• Takes a long time to draw

Use a trick instead:

• Take a picture of the real thing
• Paste that picture on the shape, like sticking on a decal

This technique is called Texture Mapping

Using image textures

Image texture:

• Uses a single image from a file in one of these formats:

GIF	8-bit lossless compressed images 1 transparency color
JPEG	Usually a poor choice for texture mapping 8-bit thru 24-bit lossy compressed images No transparency support
PNG	An adequate choice for texture mapping 8-bit thru 24-bit lossless compressed images 8-bit transparency per pixel Best choice

Using pixel textures

Pixel texture:

• A single image, given in the VRML file itself
• The image is encoded using hex
  • Up to 10 bytes per pixel
  • Very inefficient
  • Only useful for very small textures
  • Stripes
  • Checkerboard patterns

Using movie textures

Movie texture:

• A movie from an MP4 file
• The movie plays back on the textured shape

Syntax: Appearance

An Appearance node describes overall shape appearance:

• texture - texture source

XML Encoding

<Shape>
  <Appearance>
    <Material ... />
    <ImageTexture ... />
  </Appearance>
  <!-- geometry ... -->
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance {
    material Material { ... }
    texture ImageTexture { ... }
  }
  geometry ...
}

Syntax: ImageTexture

An ImageTexture node selects a texture image for texture mapping:

• url - texture image file URL

XML Encoding

<Shape>
  <Appearance>
    <Material/>
    <ImageTexture
        url='"wood.jpg"'/>
  </Appearance>
  <!-- geometry ... -->
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance {
    material Material { }
    texture ImageTexture {
      url "wood.jpg"
    }
  }
  geometry ...
}

Syntax: PixelTexture

A PixelTexture node specifies texture image pixels for texture mapping:

• image - texture image pixels
• Image data - width, height, bytes/pixel, pixel values

XML Encoding

<Shape>
  <Appearance>
    <Material/>
    <PixelTexture
        image='2 1 3
          0xFFFF00 0xFF0000'/>
  </Appearance>
  <!-- geometry ... -->
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance {
    material Material { }
    texture PixelTexture {
      image 2 1 3
        0xFFFF00 0xFF0000
    }
  }
  geometry ...
}

Syntax: MovieTexture

A MovieTexture node selects a texture movie for texture mapping:

• url - texture movie file URL
• When to play the movie, and how quickly (like a TimeSensor node)

XML Encoding

<Shape>
  <Appearance>
    <Material/>
    <MovieTexture
        url='"movie.mp4"'
        loop='true'
        speed='1.0'
        startTime='0.0'
        stopTime='0.0'/>
  </Appearance>
  <!-- geometry ... -->
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance {
    material Material { }
    texture MovieTexture {
      url "movie.mp4"
      loop TRUE
      speed 1.0
      startTime 0.0
      stopTime 0.0
    }
  }
  geometry ...
}

Using materials with textures

• Color textures override the color in a Material node
• Grayscale textures multiply with the Material node color
  • Good for colorizing grayscale textures
• If there is no Material node, the texture is applied emissively

Using transparent textures

Texture images can include color and transparency values for each pixel:

• Pixel transparency is also known as alpha

Pixel transparency enables you to make parts of a shape transparent:

• Windows, grillwork, holes
• Trees, clouds

Summary

• A texture is like a decal pasted to a shape
• Specify the texture using an ImageTexture, PixelTexture, or MovieTexture node in an Appearance node
• Color textures override material, grayscale textures multiply
• Textures with transparency create holes