OpenGL provides more features such as applying colors to an object,
scaling, lighting, rotating an object, etc. This chapter describes some
of the transformations on objects using JOGL.
This method belongs to the GLMatrixFunc interface, which is in the javax.media.opengl.fixedfunc package.
package − javax.media.opengl.fixedfunc
The following table lists some important methods of this interface −
The glTranslate() method moves the origin of the coordinate system to the point specified by the parameters (x,y,z), passed to the glTranslate() method as
argument. To save and restore the untranslated coordinate system, glPushMatrix() and glPopMatrix() methods are used.
The following code shows the template to initialize a view port and projection matrix −
Moving an Object on the Window
In earlier chapters, we discussed the programs for drawing a line and drawing various shapes using simple lines. The shapes created in this way can be displayed on any location within the window. It is done using the method glTranslatef (float x, float y, float z).This method belongs to the GLMatrixFunc interface, which is in the javax.media.opengl.fixedfunc package.
GLMatrixFunc Interface
interface − GLMatrixFuncpackage − javax.media.opengl.fixedfunc
The following table lists some important methods of this interface −
Sr.No. | Methods and Description |
---|---|
1 | void glRotatef(float angle, float x, float y, float z) Rotates the current matrix. |
2 | void glScalef(float x, float y, float z) Used to scale the current matrix. |
3 | void glTranslatef(float x, float y,float z) Used to translate the current matrix. |
4 | void glLoadIdentity() Loads the current matrix with identity matrix. |
argument. To save and restore the untranslated coordinate system, glPushMatrix() and glPopMatrix() methods are used.
gl.glTranslatef(0f, 0f, -2.5f);Whenever glTranslate() is used, it changes the position of the component on the screen. Hence, the reshape() method of GLEventListener interface should be overridden and OpenGL viewport and projection matrix should be initialized.
The following code shows the template to initialize a view port and projection matrix −
public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) { // TODO Auto-generated method stub final GL2 gl = drawable.getGL().getGL2(); // get the OpenGL 2 graphics object if(height <= 0) height = 1; //preventing devided by 0 exception height = 1; final float h = (float) width / (float) height; // display area to cover the entire window gl.glViewport(0, 0, width, height); //transforming projection matrix gl.glMatrixMode(GL2.GL_PROJECTION); gl.glLoadIdentity(); glu.gluPerspective(45.0f, h, 1.0, 20.0); //transforming model view gl.glLoadIdentity(); gl.glMatrixMode(GL2.GL_MODELVIEW); gl.glLoadIdentity(); }
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