3D Rendering with JOGL

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3D Rendering with JOGL

• Introduction to Java OpenGL Graphic Library

By Ricardo Veguilla
http//ece.uprm.edu/veguilla/java_opengl_demo/
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3D Graphics Intro

• 3D graphics are images generated from abstract
  descriptions of three dimensional objects.
• Representations of three-dimensional geometry are
  projected to a two-dimensional plane (screen) for
  viewing by a user.
• The projection process simulates the interaction
  between light and the object surfaces. This
  creates an illusion of 3D, hence the name 3D
  rendering.

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Requirements for 3D Rendering

• A virtual camera
• Decides what should end up in the final image
• A 3D scene
• Geometry (triangles, lines, points, and more)
• Light sources
• Material properties of geometry
• Textures (images to glue onto the geometry)
• A triangle consists of 3 vertices
• A vertex is 3D position, and may
  include normals and more.

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Virtual Camera

• Defined by position, direction vector, up vector,
  field of view, near and far plane.
• Create image of geometry inside gray region

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Geometry Manipulation

• Originally, an object is in model space
• Move, orient, and transform geometrical objects
  into world space
• Example, a sphere is defined with origin at
  (0,0,0) with radius 1
• Translate, rotate, scale to make it appear
  elsewhere
• Done per vertex with a 4x4 matrix multiplication!
• The user can apply different matrices over time
  to animate objects

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Example A 3D square
glTranslatef(0,7,0) glRotatef(45,0,0,2)
y
glTranslatef(8,6,0) glScalef(2,2,2)
x
glTranslatef(8,0,0)
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The Geometry Color

• Triangle color defined per vertex
• Interpolate colors over the triangle

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Texturing

• Painting images onto geometrical objects

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Geometry Projection

• Orthogonal
• Perspective

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OpenGL The Open Graphics Language

• De facto Application Programming Interface (API)
  for cross-platform development of 3D graphics
  applications.
• Implementations available for all major Operating
  Systems and hardware platforms.
• Support for hardware accelerated 3D rendering.
• Scalable, high-level, easy to use, well
  documented.

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JOGL

• Jogl is a Java programming language binding for
  the OpenGL 3D graphics API
• Supports integration with the Java platform's AWT
  and Swing widget sets
• Provides access to the latest OpenGL routines
  (OpenGL 2.0 with vendor extensions)
• Also provides platform-independent access to
  hardware-accelerated off-screen rendering.

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OpenGL - Primitive types
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Defining OpenGL primitives

• glBegin( GL_PRIMITIVE_TYPE)
• glVertex()
• glVertex()
• glEnd() Block.

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Transformation Matrices

• OpenGL provide 3 transformation matrix stacks
• Perspective Matrix Used for viewing
  transformations equivalent to positioning and
  aiming a camera.
• Modeling Matrix Used for modeling
  transformations equivalent to positioning and
  orienting the model to be drawn.
• Texture Matrix Used for texture transformations
  equivalent to positioning and orienting the
  texture to be drawn over a polygon.

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Transformation functions

• glLoadIdentity()
• glTranslate(TYPE x, TYPE y, TYPE z)
• glRotate(TYPE angle, TYPE x, TYPE y, TYPE z)
• glScale(TYPE x, TYPE y, TYPE z)
• glPushMatrix()
• glPopMatrix()

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glLoadIdentity

• glLoadIdentity()
• Loads the identity matrix into the current
  transformation matrix.
• Used to reset the current transformation matrix
  before performing a transformation.

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Translatoin

• glTranslate(TYPE x, TYPE y, TYPE z)
• Multiplies the current transformation matrix by a
  matrix that moves an object (the local coordinate
  system) by the given x, y, and z values.

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Rotation

• glRotate(TYPE angle, TYPE x, TYPE y, TYPE z)
• Multiplies the current transformation matrix by a
  matrix that rotates an object (or the local
  coordinate system) in a counter clockwise
  direction about the ray from the origin through
  the point (x, y, z). The angle parameter
  specifies the angle of rotation in degrees.

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Scaling

• glScale(TYPE x, TYPE y, TYPE z)
• Multiplies the current transformation matrix by a
  matrix that stretches, shrinks, or reflects and
  object (or the local coordinate system) along the
  axes. Each x, y, and z coordinate of every point
  in the object is multiplied by the corresponding
  argument x, y, or z.

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Controlling the transformation matrix stacks

• glPushMatrix()
• Pushed the current transformation matrix into the
  stack.
• glPopMatrix()
• Loads the matrix at the top of the stack into the
  current transformation matrix.

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OpenGL - Code Example

• // Set the viewport size
• glViewport(0, 0, width, height)
• // Clear the window
• glClear(GL_COLOR_BUFFER_BIT)
• // Set the drawing color
• glColor3f(1.0, 1.0, 1.0)
• // Start primitive type definition
• glBegin(GL_POLYGON)
• // Specify verticies
• glVertex2f(-0.5, -0.5)
• glVertex2f(-0.5, 0.5)
• glVertex2f(0.5, 0.5)
• glVertex2f(0.5, -0.5)
• // End primitive type definition
• glEnd()
• // Flush the buffer to force drawing of all
  objects thus far
• glFlush()

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References

• OpenGL - The Industry Standard for High
  Performance Graphics
• http//www.opengl.org/
• Jogl Java OpenGL Bindings
• https//jogl.dev.java.net/
• Wikipidia OpenGL
• http//en.wikipedia.org/wiki/OpenGL