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krez

generating an ellipsoid in openGL

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i am working on a model editor for my game, and it would greatly simplify the whole thing if i could have the parts of the model start out as an ellipsoid (right now they start out as a block, which requires massive amounts of editing before it looks like a body part). unfortunately, i cannot seem to generate an ellipsoid properly (in fact, the closest i get is a big mess). does anyone know where i can find c/c++ code (or even psuedo-code) that will generate an ellipsoid out of triangles? i searched with google, but to no avail. i don''t even care if it is messy; i only need to generate a few ellipsoids, and i can save them as a template or something. thanks!

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Played around a bit, and came up with this little function.
Might not be the best, but it does seem to work.

I believe the parametric equ. of an ellisoid are

x : cos(t) * cos(s)
y : cos(t) * sin(s)
z : sin(t)

-Pi/2 <= t <= Pi/2
-Pi <= s <= Pi

The function I created is as follows:


    
void DrawEllipsoid(unsigned int uiStacks, unsigned int uiSlices, float fA, float fB, float fC)
{
float tStep = (Pi) / (float)uiSlices;
float sStep = (Pi) / (float)uiStacks;
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
for(float t = -Pi/2; t <= (Pi/2)+.0001; t += tStep)
{
glBegin(GL_TRIANGLE_STRIP);
for(float s = -Pi; s <= Pi+.0001; s += sStep)
{
glVertex3f(fA * cos(t) * cos(s), fB * cos(t) * sin(s), fC * sin(t));
glVertex3f(fA * cos(t+tStep) * cos(s), fB * cos(t+tStep) * sin(s), fC * sin(t+tStep));
}
glEnd();
}
}


This will draw an ellipsoid centered at the origin, and having the "radius" around X, Y, and Z given by fA, fB, and fC respectively.

Enjoy, and post any improvements you may have.
-Evan

*EDIT* Note that it renders it in wireframe, removing the glPolygonMode call will render solid triangles.

[edited by - terminate on December 5, 2002 8:11:00 PM]

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