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I was wondering if there was an easy way to display spheres in openGL.

IE, for triangles we just go

glBegin(GL_TRIANGLES)

...

is there a way to do this with spheres?

dorbie

12-07-2004, 04:13 PM

You could use GLUT to draw a sphere but basically with OpenGL you have to draw a sphere using a bunch of triangles. That's what GLUT does. With enough triangles you stop noticing the triangles and only see the sphere. Smooth shading helps a lot with this.

Do you have any example code somewhere I can see?

Thanks for the help.

Aeluned

12-08-2004, 05:30 AM

google "gluSphere"

...or if you prefer here's some code that will generate the points for a sphere rendered as a QUAD_STRIP

int i,j;

double dRho1 = 0;

double dRho2 = 0;

double dPhi = -PI/2.;

Vert3D e,p;

double SpherePoints[iNUM_GLOBE_PTS+1][iNUM_GLOBE_PTS/2][6];

double TexPoints[iNUM_GLOBE_PTS+1][iNUM_GLOBE_PTS/2][4];

double dTexCoordX,dTexCoordY;

dTexCoordX = m_pPrimitive->m_dTexCoordX;

dTexCoordY = m_pPrimitive->m_dTexCoordY;

for (j=0;j<iNUM_GLOBE_PTS/2;j++)

{

dRho2 += PI / ((double)iNUM_GLOBE_PTS/2);

for (i=0;i<=iNUM_GLOBE_PTS;i++)

{

//e is the surface normal (in case you need it).

e.x = sin(dRho2)*cos(dPhi);

e.y = cos(dRho2);

e.z = sin(dRho2)*sin(dPhi);

p.x = dRadius * e.x;

p.y = dRadius * e.y;

p.z = dRadius * e.z;

TexPoints[i][j][0] = dTexCoordX*(i/(double)iNUM_GLOBE_PTS);

TexPoints[i][j][1] = dTexCoordY*(2*(j+1)/(double)iNUM_GLOBE_PTS);

//Lower Ring....

SpherePoints[i][j][0] = p.x;

SpherePoints[i][j][1] = p.y;

SpherePoints[i][j][2] = p.z;

e.x = sin(dRho1)*cos(dPhi);

e.y = cos(dRho1);

e.z = sin(dRho1)*sin(dPhi);

p.x = dRadius * e.x;

p.y = dRadius * e.y;

p.z = dRadius * e.z;

TexPoints[i][j][2] = dTexCoordX*(i/(double)iNUM_GLOBE_PTS);

TexPoints[i][j][3] = dTexCoordY*(2*j/(double)iNUM_GLOBE_PTS);

//Upper Ring

SpherePoints[i][j][3] = p.x;

SpherePoints[i][j][4] = p.y;

SpherePoints[i][j][5] = p.z;

dPhi -= 2*PI/(double)iNUM_GLOBE_PTS;

}

pGL->End();

dPhi = -PI/2.;

dRho1 += PI / ((double)iNUM_GLOBE_PTS/2);

}

zukko

12-08-2004, 06:22 PM

use quadratics.

GLUquadricObj *quadratic;

// on your initialization function:

quadratic = gluNewQuadric();

gluQuadricNormals(quadratic,GLU_SMOOTH);

gluQuadricTexture(quadratic,GL_TRUE);

//on your rendering function:

gluSphere(quadratic,radius,subdivisions,subdivisio ns);

//on your deinitialization function:

gluDeleteQuadric(quadratic);

Silkut

12-09-2004, 12:43 AM

yes, use quadratic with GLU

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