Transcript 3D Graphics Rendering

3D Rendering with JOGL
Introduction to Java OpenGL Graphic Library
By Ricardo Veguilla
http://ece.uprm.edu/~veguilla/java_opengl_demo/
3D Graphics Intro
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3D graphics are images generated from
abstract descriptions of three dimensional
objects.
Representations of three-dimensional
geometry are projected to a twodimensional 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.
Requirements for 3D Rendering
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A virtual camera:
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A 3D scene:
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Decides what should end up in the final image
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
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A vertex is 3D position, and may
include normals and more.
Virtual Camera
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Defined by position, direction vector, up
vector, field of view, near and far plane.
point
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dir
far
fov
near
(angle)
Create image of geometry inside gray
region
Geometry Manipulation
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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
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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
Example: A 3D square
y glTranslatef(0,7,0);
glRotatef(45,0,0,2);
glTranslatef(8,6,0);
glScalef(2,2,2);
x
glTranslatef(8,0,0);
The Geometry Color
Triangle color defined per vertex
 Interpolate colors over the triangle
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blue
red
green
Texturing
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Painting images onto geometrical
objects
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Geometry Projection
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Orthogonal
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Perspective
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
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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 offscreen rendering.
OpenGL - Primitive types
Defining OpenGL primitives
glBegin( GL_PRIMITIVE_TYPE)
glVertex(…)
glVertex(…)
…
glEnd() Block.
Transformation Matrices
OpenGL provide 3 transformation matrix
stacks:
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Perspective Matrix – Used for viewing
transformations – equivalent to positioning and
aiming a camera.
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Modeling Matrix – Used for modeling
transformations – equivalent to positioning and
orienting the model to be drawn.
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Texture Matrix – Used for texture
transformations – equivalent to positioning and
orienting the texture to be drawn over a
polygon.
Transformation functions
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glLoadIdentity()
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glTranslate(TYPE x, TYPE y, TYPE z)
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glRotate(TYPE angle, TYPE x, TYPE y, TYPE z)
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glScale(TYPE x, TYPE y, TYPE z)
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glPushMatrix()
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glPopMatrix()
glLoadIdentity
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glLoadIdentity()
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Loads the identity matrix into the current
transformation matrix.
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Used to reset the current transformation
matrix before performing a transformation.
Translatoin
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glTranslate(TYPE x, TYPE y, TYPE z)
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Multiplies the current transformation matrix
by a matrix that moves an object (the local
coordinate system) by the given x, y, and z
values.
Rotation
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glRotate(TYPE angle, TYPE x, TYPE y,
TYPE z)
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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.
Scaling
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glScale(TYPE x, TYPE y, TYPE z)
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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.
Controlling the transformation
matrix stacks
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glPushMatrix()
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Pushed the current transformation
matrix into the stack.
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glPopMatrix()
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Loads the matrix at the top of the
stack into the current transformation
matrix.
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();
References:
OpenGL - The Industry Standard for
High Performance Graphics
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http://www.opengl.org/
Jogl – Java OpenGL Bindings
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https://jogl.dev.java.net/
Wikipidia – OpenGL
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http://en.wikipedia.org/wiki/OpenGL