Chap 7. OpenGL extension

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Chap 7. OpenGL extension
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How to

• By yourself
• Query the OpenGL32.dll, and get the function
  address
• Dont do it
• glew
• http//glew.sourceforge.net/

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In your C project

• Add include/glew.h to your Include Files
  folder in .NET
• Put lib/glew32s.lib into your project folder
• define GLEW_STATIC 1
• include "glew.h
• glutInit(argc, argv)
• glewInit()

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Some online resources

• OpenGL programming guide chapter 9 Texture
  Mapping
• http//www.opengl.org/documentation/red_book_1.0/O
  penGL_PG_ch09.pdf
• An online tutorial on shadow map
• http//www.paulsprojects.net/tutorials/smt/smt.htm
  l

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Example Shadow map

• What is shadow

light
eye
Object
Under shadow
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What is a shadow map

• A depth image as seen from the light
• When the depth of a point is greater than the
  depth in the shadow map, it is under shadow
• If you move the viewpoint to the light source
  position, there are no shadows from that
  perspective

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Overview

• 3-pass algorithm
• First pass render the scene from the point of
  view of the light,and store the depth in the
  texture (shadow map)
• projection modelview,
• Second pass render the scene with only ambient
  light
• Third pass render the scene,and compare the
  depth of the fragment to the shadow map, if its
  greater than the depth in the shadow map, its
  under shadow. if its not under shadow, render
  the fragment with diffuse and specular light.
• How can we compare in different coordinate?

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How can we compare in different coordinate
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The transformation matrix
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In OpenGL

• First pass
• Setup the projection and modelview matrix as
  seen from the light
• draw your scene
• glGenTextures(1, texID)
• glBindTexture(GL_TEXTURE_2D, texID)
• glCopyTexImage2D( GL_TEXTURE_2D, 0,
  GL_DEPTH_COMPONENT, 0, 0,
• SHADOW_MAP_WIDTH, SHADOW_MAP_HEIGHT, 0 )

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• void glCopyTexImage2D(
• GLenum target,
• GLint level,
• GLint internalFormat,
• GLint x, GLint y,
• GLsizei width, GLsizei height,
• GLint border)

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• Third pass
• void generateTextureMatrix( float lightPos )
• glMatrixMode(GL_TEXTURE)
• glLoadIdentity()
• glTranslatef( 0.5, 0.5, 0.0 )
• glScalef( 0.5, 0.5, 1.0 )
• gluPerspective( 80.0, 1.0, 10.0, 100.0 )
• gluLookAt( lightPos0, lightPos1,
  lightPos2,
• 0.0, 0.0, 0.0,
• 0.0, 1.0, 0.0)
• glEnable( GL_TEXTURE_GEN_S )
• glEnable( GL_TEXTURE_GEN_T )
• glEnable( GL_TEXTURE_GEN_R )
• glEnable( GL_TEXTURE_GEN_Q )

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• float sPlane4 1.0, 0.0, 0.0, 0.0
• float tPlane4 0.0, 1.0, 0.0, 0.0
• float rPlane4 0.0, 0.0, 1.0, 0.0
• float qPlane4 0.0, 0.0, 0.0, 1.0
• glTexGeni( GL_S, GL_TEXTURE_GEN_MODE,
  GL_EYE_LINEAR )
• glTexGeni( GL_T, GL_TEXTURE_GEN_MODE,
  GL_EYE_LINEAR )
• glTexGeni( GL_R, GL_TEXTURE_GEN_MODE,
  GL_EYE_LINEAR )
• glTexGeni( GL_Q, GL_TEXTURE_GEN_MODE,
  GL_EYE_LINEAR )
• glTexGenfv( GL_S, GL_EYE_PLANE, sPlane )
• glTexGenfv( GL_T, GL_EYE_PLANE, tPlane )
• glTexGenfv( GL_R, GL_EYE_PLANE, rPlane )
• glTexGenfv( GL_Q, GL_EYE_PLANE, qPlane )

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• glTexParameteri( GL_TEXTURE_2D,
  GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE )
• glTexParameteri( GL_TEXTURE_2D,
  GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE )
• glTexParameteri( GL_TEXTURE_2D,
  GL_TEXTURE_MIN_FILTER, GL_LINEAR )
• glTexParameteri( GL_TEXTURE_2D,
  GL_TEXTURE_MAG_FILTER, GL_LINEAR )
• glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,
  GL_MODULATE)
• glTexParameteri( GL_TEXTURE_2D,
  GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL )
• glTexParameteri( GL_TEXTURE_2D,
  GL_DEPTH_TEXTURE_MODE, GL_LUMINANCE )
• glTexParameteri( GL_TEXTURE_2D,
  GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE
  )
• glMatrixMode(GL_MODELVIEW)

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Not so easy

• Self shadow
• Add bias
• glPolygonOffset(GLfloat factor, GLfloat units)
• Render backface and cull front face when
  gererating shadow map
• Aliasing