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3D Rendering with JOGL

3D Rendering with JOGL . Introduction to Java OpenGL Graphic Library. By Ricardo Veguilla. http://ece.uprm.edu/~veguilla/java_opengl_demo/. 3D Graphics Intro. 3D graphics are images generated from abstract descriptions of three dimensional objects .

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3D Rendering with JOGL

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  1. 3D Rendering with JOGL Introduction to Java OpenGL Graphic Library By Ricardo Veguilla http://ece.uprm.edu/~veguilla/java_opengl_demo/

  2. 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.

  3. 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.

  4. far dir point fov (angle) near Virtual Camera • Defined by position, direction vector, up vector, field of view, near and far plane. • Create image of geometry inside gray region

  5. 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

  6. 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);

  7. blue red green The Geometry Color • Triangle color defined per vertex • Interpolate colors over the triangle

  8. + = Texturing • Painting images onto geometrical objects

  9. Geometry Projection • Orthogonal • Perspective

  10. 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.

  11. 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.

  12. OpenGL - Primitive types

  13. Defining OpenGL primitives glBegin( GL_PRIMITIVE_TYPE) glVertex(…) glVertex(…) … glEnd() Block.

  14. 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.

  15. 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()

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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  21. 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();

  22. 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

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