Ball

Dunge · 2000-10-25T15:45:40

Hey i''m a newbie and I''m doing the NeHe tutorials...... I jsut finished the blending one.... but I have a question : how can we create a sphere and not a cube? I don''t know...... maybe it''s a simple command that we put the position of the center of the ball and how long the radius is? anyway please help me!

wolfman8k

140

October 16, 2000 04:43 PM

A small correction: You can make a sphere out of Quads AND Triangles(or just Triangles).

Also, there are two main kinds of spheres: "normal" ones(I don''t know the technical name) and "geospheres". geosphere''s are usually used in games, and can only be made with triangles.

Dunge

Author

405

October 16, 2000 05:14 PM

Hey....... I only want to do a ball in a PONG game and I want an exemple of gluSphere (C++) I seen in the MSDN but I don''t understand how to use it.....

void gluSphere( GLUquadricObj *qobj, GLdouble radius, GLint slices, GLint stacks );

slices and stacks are the number of line in the ball vertical and horizontal, radius is the size but qobj?

oglman

122

October 16, 2000 09:05 PM

    //During global variable declaration add the line:GLUquadricObj *quadratic;//At the end of your InitGL function add:quadratic=gluNewQuadric();gluQuadricNormals(quadratic, GLU_SMOOTH);gluQuadricTexture(quadratic, GL_TRUE);//Then during your DrawGLScene function add the function:gluSphere(quadratic, [radius], [slices], [stacks]);

That is coming straight out of NeHe tutorial 18 on quadratics and there may be something that is missing in there.

quote:

by GLUT u mean the glu functions?

I think nate means the functions contained in the GLUT.H header file.

Edited by - oglman on October 16, 2000 10:19:59 PM

baskuenen

124

October 16, 2000 09:33 PM

You can do it yourself:

    //---------------------------------------------------------------------------void __fastcall CObject::Draw(){	//	Ball	for(int z=0; z<8; z++)	{		glBegin(GL_QUAD_STRIP);		for(int r=0; r<=16; r++)		{			glNormal3d(				cos(2*PI/16*r) * sin(2*PI/16*z),				sin(2*PI/16*r) * sin(2*PI/16*z),				cos(2*PI/16*z));			glVertex3d(				Object.Position.x + dSize * cos(2*PI/16*r) * sin(2*PI/16*z),				Object.Position.y + dSize * sin(2*PI/16*r) * sin(2*PI/16*z),				Object.Position.z + dSize * cos(2*PI/16*z));			glNormal3d(				cos(2*PI/16*r) * sin(2*PI/16*(z+1)),				sin(2*PI/16*r) * sin(2*PI/16*(z+1)),				cos(2*PI/16*(z+1)));			glVertex3d(				Object.Position.x + dSize * cos(2*PI/16*r) * sin(2*PI/16*(z+1)),				Object.Position.y + dSize * sin(2*PI/16*r) * sin(2*PI/16*(z+1)),				Object.Position.z + dSize * cos(2*PI/16*(z+1)));		}		glEnd();	}}//---------------------------------------------------------------------------

You have to replace the 8 and 16 values with the amount of vertices you want.

Does someone know how to calculate a sphere with even-sized polygons? Or have a link to some interresting stuff about this?

sinistrx

122

October 16, 2000 11:58 PM

Will that code right there run faster than Glusphere with Backface culling enabled?

baskuenen

124

October 17, 2000 12:51 AM

sinistrx: To be honest - I don''t have a clue

But the code can be optimized. Just a few:

Calc the sin/cos only once. Also every other value used twice or more, can be calced only once.

Do it in assembly.

Use floats - not doubles.

Unrolled loops in some situations (hehe - just kidding

)

Don''t multiply but interpolate using pre-calculated values.

Optimisation is endless work...

Just a few reasons why this code could be faster:

More calculations can be pre-calculated because. For instance: the size/position/slices can be a constant.

You don''t need an extra glTranslate().

Another advantage:

You can enter your own glTexCoord() and/or glColor() values.

It''s fun to do it yourself

You can add other strange effects...!

I don''t know much about glut, so I can''t say what is faster...
But glut is just another OpenGL wrapper. I don''t want to start a war about this, it''s just that personally I like to stay as low level as I can. Maybe others do too - that''s why I posted this answer.

oglman

122

October 17, 2000 04:48 PM

I was just telling him how to use gluSphere() not suggesting anything about hoe efficiant it is

zedzeek

529

October 17, 2000 06:06 PM

the source of glut is included with the distribution so u can have a looksy to see what glutsolidsphere does
also check out the mesa source

http://members.xoom.com/myBollux

Captain Courgette, eat more veg

Gladiator

127

October 17, 2000 07:41 PM

Where can I download the SDK and the runtime for OpenGL? Thanks!

-------------------------------
I'll screw up whoever screws around with the gamedev forum!

..-=gLaDiAtOr=-..

Gladiator

127

October 17, 2000 09:34 PM

So many people use it and nobody knows?

-------------------------------
I'll screw up whoever screws around with the gamedev forum!

..-=gLaDiAtOr=-..

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