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06-17-2003, 05:17 PM
please help me....i really need to know how to create this thing with openGL.can somebody help me.i'm new in openGL

mikael_aronsson
06-17-2003, 10:18 PM
Hi !

You use DDA (Digital Differential Analyzer) for lines and sin and cos for circles and ellipses, use google to search for it.

OpenGL already has support for lines so I don't know why you need it, circles and ellipses area very easy (just draw line segments between the caclulated points using GL_LINESTRIP.

Something like this:
x = xpos + xradius * cos( v)
y = ypos + yradius * sin( v)

If I remember correct http://www.opengl.org/discussion_boards/ubb/biggrin.gif, v is the angle in radians (2*pi is a full circle).

Mikael

This pdf might get you started: www.cs.ucr.edu/~vbz/cs130-03.pdf (http://www.cs.ucr.edu/~vbz/cs130-03.pdf)

Mikael

Sourpotato
06-18-2003, 04:36 PM
Originally posted by mael:
please help me....i really need to know how to create this thing with openGL.can somebody help me.i'm new in openGL

/*
for the line
*/
glBegin(GL_LINES);
glVertex3f(1.0f,0.0f,0.0f);
glVertex3f(0.0f,0.0f,0.0f);
glEnd();

//for the circle or elipse
first when you set your projection mode
you need to use glOrtho

you can use either DDA or midpoint algorithm (also called bresenham algorithm )to draw the circle or elipse

Also you can use gluSphere ,check the REDbook/msdn for the more detailed explaination

[This message has been edited by RunningRabbit (edited 06-18-2003).]

[This message has been edited by RunningRabbit (edited 06-19-2003).]