Open GL Texture and Bump Mapping

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Open GL Texture and Bump Mapping

• COSC 471
• Professor Schmitt
• Matthew Devilbiss
• 3/13/07

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Abstract

• This presentation will cover the topics of
  texture and bump mapping to produce a more
  realistic 3D image. Texture mapping will receive
  primary focus with details on the how to
  implement it and which OpenGL functions should be
  used.

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Overview

• Texture Mapping
• Definition
• How to implement
• Uses
• Bump Mapping
• Definition
• Explanation
• Simple Implementation

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What is texture mapping

• A method to add a color, pattern, or texture to a
  3D model.
• Think of a flat rectangular shaped model
• Take that model and map a texture to it in order
  to create a chess board, cardboard box, or
  anything else you can think of.

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What is a Texture Map?

• An image that can be attached to a polygon
• Stored as an array
• Can be mapped to non rectangular objects such as
  spheres, squares, and other various 3D models.

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Types of Texture Maps

• There are three main types of texture maps
• These are 1D, 2D and 3D.
• 2D are the most prevalent

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Example 2D Texture
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Example 3D texture
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Requirments

• A texture
• OpenGL
• An API that supports rendering textures onto
  polygons.

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How are they mapped?

• The texture is given a coordinate system.

(1.0, 1.0)
(0.0, 1.0)
(1.0, 0.0)
(0.0, 0.0)
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How to texture mapStep One

• First you must enable texturing
• Call glEnable(GL_TEXTURE_2D)
• This enables 2D texturing.

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How to texture mapStep Two

• You must now declare a Texture object
• Texture objects are special internal
  representations of your texture.
• Declare one by coding
• texture1 new CTargaImage

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How to texture mapStep Three

• Now you have to upload the texture to video
  memory.
• Use
• Load(image file)
• This loads the texture into memory

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How to texture mapStep Four

• Now you have to bind the texture object
• This is done using glBindTexture()
• Example
• glBindTexture(GL_TEXTURE_2D, m_textureObjectOne)

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How to texture mapStep Five

• Now you set the filtering properties for your
  texture.
• Filtering handles how OpenGL displays your
  texture from different distances.
• Use GLTexParameter()

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How to texture mapStep Six

• Now you must specify the texture
• Call this function to do so
• glTexImage2D()
• This has 9 parameters.

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How to texture mapStep Seven

• Now draw a polygon
• When drawing a polygon use these functions.
• glTexCoord(0.1, 0.3) this specifies the texture
  coordinates.
• glVertex() this tells the OpenGl to apply a
  particular texture to a particular vertex.

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Finally Done

• When OpenGl draws the polygon it should be mapped
  with the texture that you specified.

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Uses of texture binding

• Now that you can texture map what is it good for?
• You can make a bland polygon more realistic.
• Add great detail to an image

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Who uses texture mapping

• Any game will use texture mapping.
• Computer generated videos
• Simulations
• Graphic art

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Recap

• 1. Enable texturing
• 2. Load the texture image data
• 3. Declare a texture object
• 4. Bind the texture object
• 5. Set up filtering
• 6. Specify a texture for the texture object
• 7. Draw a polygon and specify texture coordinates

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Bump Mapping

• Bump mapping changes the surface of a 3D model
• This is done to make objects look more realistic.
  
• This lets a polygons texture appear 3D.

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Requirments

• The GPU must have a vertex shader or a vector
  processing unit
• It must be fast enough so it doesnt bog down
  calculating each bump

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Example
Without Bump Mapping
With Bump Mapping
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How to Bump Map

• The simplest method uses fragment shaders to
  produce the actual bumps.
• First you must create a height map which is
  usually an array of texels identical to the
  texture being mapped.
• The height map is used to determine how high or
  low the bump will be

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Bump Mapping step 2

• Once the height map is created you must take the
  light and view vectors of each texel
• Using the height map you can change the vectors
  of the texture.
• These changes produce a more detailed image.

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Who uses bump mapping

• Many games
• CG movies and graphic artists
• Anything that requires a more realistic depth

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Conclusion

• Texture and Bump Mapping can create a more
  realistic image
• Both techniques require some skill but are
  essential to producing detailed images
• Open GL supports both techniques
• A good video card with vertex shaders will easily
  produce both

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Questions?

• Any Questions???