gluSphere and quadratic objects

Dear All,

I posted a question a little while ago (entitled "gl animation too slow"). Thanks for all the suggestions.
I have another related question, which might help me speed things up.
In my code, I call gluSphere several thousand times ( ), but I can't allow this to take long.
I see that gluSphere takes a GLUquadricObj as a parameter. Does this mean that the sphere is now stored in this quadratic object? If so, then since I want all my spheres to look the same, can I re-use that objcet, rather than calling gluSphere time and again?
If so, how? I don't know how I would re-render such an object. (Re-render is probably not the word I should use - I hope you understand what I mean).

Thanks everyone,

Phil Drew

If it helps, here's my code again:

Code:

	::glNewList(1,GL_COMPILE_AND_EXECUTE);

	for(i=0; i<m_ppf; i++)
	{
		n = m_ppf*f + i;
		X = m_x[n];
		Y = m_y[n];
		Z = m_z[n];

		glPushMatrix();
			glTranslated(X, Y, Z);
			glColor3f(1.0f,1.0f,1.0f);
			glMaterialfv(GL_FRONT,GL_DIFFUSE,farraygrey);
			gluSphere(m_quadratic, m_radius, m_quality+1, m_quality+1);
		glPopMatrix();
	}

	::glEndList();

Again I'm not sure of this glSphere stuff but I do have code from NVidia which creates a sphere mathematically.

Using the newer video cards ability to add and remove vertexes on the fly you could do the following and forget the quadratic.

1. Pre-render a sphere at set size and radius and save the vertexes.
2. To create a new sphere simply add or subtract vertexes and translate new vertexes by the amount needed to get a new radius.
3. Render the new sphere.


This would be very fast and would require next to nil in clock cycles.

I don't know how to add or remove vertexes in OpenGL - basically its a real time optimized adapting mesh kinda like a ROAM terrain engine...but NVidia provides native support for doing this. Check out the DirectX SDK example. They start with a lion-type model and then allow you to add complexity or remove it in real-time. This is what I'm referring to.

So pre-render the base sphere based on the following formula.


0<alpha<360
-90<beta<90

newx=centerx+((cos(alpha)*cos(beta))*radius)
newy=centery+((cos(alpha)*sin(beta))*radius)
newz=centerz+((sin(alpha))*radius)

Create a base mesh out of this and then to create a new sphere - simply add vertexes to the base mesh, and translate them by (desiredradius-baseradius).

Thanks for that - I've actually tried that (practically given myself a hernia trying to figure out all the maths for myself), but it never gives as good a sphere as gluSphere - no idea why.

But it's OK now anyway - there was a simple solution. Just make one sphere (using gluSphere) inside a glList, and then keep recalling that list when making the bigger world list.

Sod's Law that I come up with the solution 5 minutes after I post the question after a week of trying to work it out!

Thanks anyway everybody!