Identifisering
Computer Graphics
Børre Stenseth
JOGL>Lamps

A Table Lamp

What

This module describes the rendering and manipulation of 4 simple table lamps.

The lamps are completely constructed with quadrics. They have 4 manipulatable angles, each of them can be manipulated directly by mouse actions.

lamps

Structure

The lamp consist of cylinders (the foot, the two arms and the lamp shade). Each joint is marked with a sphere.

enlampe fig1

oneLamp

The lamps are placed on a round "table" in the xy-plane. A lamp is implemented in class oneLamp:

package tablelamp;
import javax.media.opengl.GL;
import javax.media.opengl.glu.GLU;
import javax.media.opengl.glu.GLUquadric;
/**
 *
 * @author borres
 */
public class oneLamp 
{
    // nice to have
    private final float G2R=0.01745277777778f;
    private final float R2G=57.29577951308f;
    //id for lamp
    int m_LampID;    
    // the geometry of the lamp
    // length of the three arms
    int[] m_Arm={40,50,10};
    // angles for armposition:
    // thickness of arm
    int m_ArmW=3;
    // radius for spheres in elbows
    int m_ElbowRadius=6;
    // base board
    int m_BaseRadius=40;
    int m_BaseHeight=2;
    // lamps head
    float m_TopR=10;
    float m_OpenR=30;
    float m_HeadCyl=30;
    float m_HeadSpread=30;;
    
    // angles for each rotation
    float    m_v1=0.0f;
    float    m_v2=0.0f;
    float    m_v3=10.0f;
    float    m_v4=30.0f;
    
    // spot smoothness
    float m_SpotExp=0.0f;
    // quadric drawing precision
    int nLong=10;
    int nRound=20;
    // which lightsource
    int m_MyLight;
    boolean    m_LampIsOn=false;

    public oneLamp(int LampID)
    {

        m_MyLight=GL.GL_LIGHT0+LampID+1;
        m_LampID=LampID;
    }
    public void draw(GL gl)
    {
    GLU glu=new GLU();
    // preserve modelview
    gl.glPushMatrix();
    if(!m_LampIsOn)
        gl.glDisable(m_MyLight);
    // use a quadric to draw parts of lamp
    GLUquadric glpQ=glu.gluNewQuadric();
    // material
    int baseMaterial=stdMaterials.MAT_GREEN_PLASTIC;
    int elbowMaterial=stdMaterials.MAT_GREEN_PLASTIC;
    int armMaterial=stdMaterials.MAT_WARM_WHITE;
    // scale the integer coordinates down to unit box
    gl.glScalef(0.01f,0.01f,0.01f);
    // display the lamp
    // use lightsource as ID for lamp
    gl.glLoadName(m_LampID*10+0);
    // base, foot
    stdMaterials.setMaterial(gl,baseMaterial,GL.GL_FRONT);
    gl.glTranslatef(0.0f,0.0f,(float)-m_BaseHeight);
    glu.gluDisk(glpQ,0.0f,(float)m_BaseRadius,20,20);
    glu.gluCylinder(glpQ,(float)m_BaseRadius,(float)m_BaseRadius,
                         (float)m_BaseHeight,nRound,nLong);
    gl.glTranslatef(0.0f,0.0f,(float)m_BaseHeight);
    glu.gluDisk(glpQ,0,(float)m_BaseRadius,nRound,nRound);
    stdMaterials.setMaterial(gl,elbowMaterial,GL.GL_FRONT);
    glu.gluSphere(glpQ,(float)m_ElbowRadius,20,20);
    // first arm, basic orientation around z-axis
    gl.glLoadName(m_LampID*10+1);
    gl.glRotatef(m_v1,0.0f,0.0f,1.0f);
    // from now on all arms are rotated around y-axis
    gl.glRotatef(m_v2,0.0f,1.0f,0.0f);
    stdMaterials.setMaterial(gl,armMaterial,GL.GL_FRONT);
    glu.gluCylinder(glpQ,m_ArmW,m_ArmW,m_Arm[0],nRound,nLong);
    gl.glTranslatef(0.0f,0.0f,(float)m_Arm[0]);
    
    stdMaterials.setMaterial(gl,elbowMaterial,GL.GL_FRONT);
    glu.gluSphere(glpQ,m_ElbowRadius,nRound,nRound);
    // second arm
    gl.glLoadName(m_LampID*10+2);
    gl.glRotatef(m_v3,0.0f,1.0f,0.0f);
    stdMaterials.setMaterial(gl,armMaterial,GL.GL_FRONT);
    glu.gluCylinder(glpQ,m_ArmW,m_ArmW,m_Arm[1],nRound,nLong);
    gl.glTranslatef(0.0f,0.0f,(float)m_Arm[1]);
    stdMaterials.setMaterial(gl,elbowMaterial,GL.GL_FRONT);
    glu.gluSphere(glpQ,m_ElbowRadius,nRound,nRound);

    // head
    gl.glLoadName(m_LampID*10+3);
    gl.glTranslatef(0.0f,0.0f,(float)m_ElbowRadius);
    gl.glRotatef(m_v4,0.0f,1.0f,0.0f);
    gl.glTranslatef(0.0f,0.0f,(float)-m_HeadCyl/2.0f);
    stdMaterials.setMaterial(gl,elbowMaterial,GL.GL_FRONT);
    glu.gluDisk(glpQ,0.0,m_TopR,nRound,nRound);
    glu.gluCylinder(glpQ,m_TopR,m_TopR,m_HeadCyl,nRound,nLong);
    gl.glTranslatef(0.0f,0.0f,(float)m_HeadCyl);
    glu.gluCylinder(glpQ,m_TopR,m_OpenR,m_HeadSpread,nRound,nLong);
    //lighton
    // lightbulb and inner screen
    if(m_LampIsOn)
    {
        // light inside of head
        stdMaterials.setMaterial(gl,stdMaterials.MAT_BRIGHT_WHITE,GL.GL_FRONT);
        glu.gluCylinder(glpQ,m_TopR-0.1f,m_OpenR-0.1f,m_HeadSpread,nRound,nLong);
        
        // specify and set the spotlight
        float spambient[] =    {0.2f,0.2f,0.2f,1.0f };
        float spdiffuse[] =    {0.8f,0.8f,0.8f,1.0f };
        float spspecular[] =    {0.8f,0.8f,0.8f,1.0f };
        float spposition[] =    {0.0f,0.0f,0.0f,1.0f};
        float spdirection[] = {0.0f,0.0f,1.0f};
        float spotangle= R2G*(float)Math.atan((m_OpenR-m_TopR)/m_HeadSpread)+10;
        gl.glLightfv(m_MyLight, GL.GL_AMBIENT,        spambient,0);
        gl.glLightfv(m_MyLight, GL.GL_DIFFUSE,        spdiffuse,0);
        gl.glLightfv(m_MyLight, GL.GL_SPECULAR,        spspecular,0);
        gl.glLightfv(m_MyLight, GL.GL_POSITION,        spposition,0);
        gl.glLightfv(m_MyLight, GL.GL_SPOT_DIRECTION,    spdirection,0);
        gl.glLightf (m_MyLight, GL.GL_SPOT_CUTOFF,    spotangle);
        gl.glLightf(m_MyLight, GL.GL_SPOT_EXPONENT, m_SpotExp);
        gl.glEnable(GL.GL_LIGHTING);
        gl.glEnable(m_MyLight);
        // light the bulb
        float[] ev={1.0f,1.0f,1.0f};
        float[] nev={0.0f,0.0f,0.0f};
        gl.glMaterialfv(GL.GL_FRONT,GL.GL_EMISSION,ev,0);
        gl.glTranslatef(0.0f,0.0f,m_HeadSpread/5.0f);
        glu.gluSphere(glpQ,m_TopR,nRound,nRound);
        gl.glMaterialfv(GL.GL_FRONT,GL.GL_EMISSION,nev,0);
    }
    glu.gluSphere(glpQ,m_TopR,nRound,nRound);
   //eoflighton
    // finished with quadric, kill it
    glu.gluDeleteQuadric(glpQ);
    // reset matrix
    gl.glPopMatrix();
    }
    public float GetAngle(int ix)
    {
        switch(ix)
        {
        case 0: return m_v1;
        case 1:return m_v2;
        case 2:return m_v3;
        case 3:return m_v4;
        default: return 0.0f;
        }
    }
    public void SetAngle(int x,float v)
    {
        switch(x)
        {
        case 0:m_v1=v; break;
        case 1:m_v2=v; break;
        case 2:m_v3=v; break;
        case 3:m_v4=v; break;
        default: ;
        }
    }
    public void SetLightOn(boolean on){m_LampIsOn=on;}
    public boolean GetLightOn() {return m_LampIsOn;}
    public void setSpotExponent(int v) {m_SpotExp=v/10.0f;}
}

Rendering

The class GLrenderer controls the rendering of the scene and selection of lamp or lamp part. The lamps are kept in :

private Vector<oneLamp> pLamp

The method display administrates the rendering:

public void display(GLAutoDrawable drawable)
{
    GL gl = drawable.getGL();
    // Clear the color and depth buffers.
    gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
    if(m_pressed)// we have pressed right mousebutton
    {
        m_pressed=false;
        int n=pickSelected(m_thePanel.getGL(),m_lastX,m_lastY);
        if(n!=NO_OBJECT)
        {
            m_hilitedPart=n%10; // lamp part
            m_hilitedLamp=n/10; // lampindex
            m_bIsManipulating=true;
        }
        else
        {
            m_hilitedLamp=NO_OBJECT; // to make sure
        }            
    }
    DrawScene(gl);
}

The method DrawScene goes like this:

private void DrawScene(GL gl)
{
    GLU glu=new GLU();
    // Set up for scene
    gl.glMatrixMode(GL.GL_MODELVIEW);
    gl.glLoadIdentity();
    glu.gluLookAt(m_zx,m_zy,m_zz,   // eye
                0.0f,0.0f,0.0f,     // VRF
                0.0f,0.0f,1.0f);    // VUP
    // interactive movement
    // rotate around z-axis
    gl.glRotatef(m_zv,0.0f,0.0f,1.0f);
    // rotate around x-axis
    gl.glRotatef(m_xv,1.0f,0.0f,0.0f);
     // set a name;NO_OBJECT on anything irrelevant we draw
    gl.glLoadName(NO_OBJECT);
    GLUquadric glpQ=glu.gluNewQuadric();
    //----------------
    // draw table
    gl.glPushMatrix();
    gl.glTranslatef(0.0f, 0.0f, -0.01f);
    stdMaterials.setMaterial(gl, stdMaterials.MAT_EMERALD, GL.GL_FRONT_AND_BACK);
    glu.gluDisk(glpQ,0.0,2.0,table_res,table_res);
    gl.glPopMatrix();
    //-----------------
    // draw lamps
    // lamp 0
    gl.glPushMatrix();
    gl.glTranslatef(-1.0f,1.0f,0.0f);
    gl.glLoadName(0);
    pLamp.elementAt(0).draw(gl);
    gl.glPopMatrix();
    // lamp 1
    gl.glPushMatrix();
    gl.glTranslatef(1.0f,1.0f,0.0f);
    gl.glLoadName(1);
    pLamp.elementAt(1).draw(gl);
    gl.glPopMatrix();
    // lamp 2
    gl.glPushMatrix();
    gl.glTranslatef(1.0f,-1.0f,0.0f);
    gl.glLoadName(2);
    pLamp.elementAt(2).draw(gl);
    gl.glPopMatrix();
    // lamp 3
    gl.glPushMatrix();
    gl.glTranslatef(-1.0f,-1.0f,0.0f);
    gl.glLoadName(2);
    pLamp.elementAt(3).draw(gl);
    gl.glPopMatrix();
    // set a name on anything irrelevant we draw
    gl.glLoadName(NO_OBJECT);
    // finnish drawing
    gl.glFlush();
}

Naming

we know that we have to set a name for each part of the scene we want to identify by pointing. In this solution this means that we must identify which lamp and which part of the lamp. We use the strategy that the lamps are numbered from 0, and the parts are numbered as 10*lamppnumber + partnumber. In DrawScene:

	// lamp 1
	gl.glPushMatrix();
	gl.glTranslatef(1.0f,1.0f,0.0f);
	gl.glLoadName(1);
	pLamp.elementAt(1).draw(gl);
	gl.glPopMatrix();
 

and in each lamps draw:

 	// first arm, basic orientation around z-axis
	gl.glLoadName(m_LampID*10+1);
	...
 

The hit mechanism is identical to the strategy used in Selection and is implemented in method pickSelected in GLRenderer.

Light Effect

The light is a combination of three effects.

  • We want to set up a spotlight that "fits" in the lamp shade
  • We want the light bulb to look "lighted"
  • We we want to make the inside of the lamp shade to look lighted
// lightbulb and inner screen
 if(m_LampIsOn)
 {
     // light inside of head
     stdMaterials.setMaterial(gl,stdMaterials.MAT_BRIGHT_WHITE,GL.GL_FRONT);
     glu.gluCylinder(glpQ,m_TopR-0.1f,m_OpenR-0.1f,m_HeadSpread,nRound,nLong);
     
     // specify and set the spotlight
     float spambient[] =    {0.2f,0.2f,0.2f,1.0f };
     float spdiffuse[] =    {0.8f,0.8f,0.8f,1.0f };
     float spspecular[] =    {0.8f,0.8f,0.8f,1.0f };
     float spposition[] =    {0.0f,0.0f,0.0f,1.0f};
     float spdirection[] = {0.0f,0.0f,1.0f};
     float spotangle= R2G*(float)Math.atan((m_OpenR-m_TopR)/m_HeadSpread)+10;
     gl.glLightfv(m_MyLight, GL.GL_AMBIENT,        spambient,0);
     gl.glLightfv(m_MyLight, GL.GL_DIFFUSE,        spdiffuse,0);
     gl.glLightfv(m_MyLight, GL.GL_SPECULAR,        spspecular,0);
     gl.glLightfv(m_MyLight, GL.GL_POSITION,        spposition,0);
     gl.glLightfv(m_MyLight, GL.GL_SPOT_DIRECTION,    spdirection,0);
     gl.glLightf (m_MyLight, GL.GL_SPOT_CUTOFF,    spotangle);
     gl.glLightf(m_MyLight, GL.GL_SPOT_EXPONENT, m_SpotExp);
     gl.glEnable(GL.GL_LIGHTING);
     gl.glEnable(m_MyLight);
     // light the bulb
     float[] ev={1.0f,1.0f,1.0f};
     float[] nev={0.0f,0.0f,0.0f};
     gl.glMaterialfv(GL.GL_FRONT,GL.GL_EMISSION,ev,0);
     gl.glTranslatef(0.0f,0.0f,m_HeadSpread/5.0f);
     glu.gluSphere(glpQ,m_TopR,nRound,nRound);
     gl.glMaterialfv(GL.GL_FRONT,GL.GL_EMISSION,nev,0);
 }
 glu.gluSphere(glpQ,m_TopR,nRound,nRound);

Note the use of GL_SPOT_EXPONENT that softens the edges of the spot. Comined with the granularity of the table, we can control the light effect. Both the spot exponent and the granularity can be manipulated in the application. See also Module Shades and smoothness

  • Lamp project: https://svnit.hiof.no/svn/psource/JOGL/lamp
Maintainance
B.Stenseth, june 2009
JOGL>Lamps
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