In the OpenGL Computer graphics there major problem in drawing circle. In this post we are going to study How to Draw Circle in OpenGL. There is no primitive functions like of lines, points, triangles and other polygons for circle, hence drawing a circle need some new method/function from our side. we are going to learn that today.

There are many methods of Drawing circle in OpenGL, we going to discuss one by one each of them.

### First Method - using the indefinite points

This method used the no of of point to draw a circle. The problem with this method is you need more precession as we use the sine and cosine function with the

*value of pie as 3.14159*, So little error may in the round circle. Put the following code in a simple display function and run the program for your circle. See the Image it's output -*glBegin(GL_POINTS);*

*for(int i=0;i<1000;++i)*

*{*

*glVertex3f(cos(2*3.14159*i/1000.0),sin(2*3.14159*i/1000.0),0);*

*}*

*glEnd();*

### Second Method - using the lines

As Like above program circles can be created using the small sets of lines.We used the bunch of lines, which are closed together to go round forming a circle. For

**drawing circle in opengl**, this method also used the simple sine and cosine maths functions, but we have*not used pie*instead go for degree for angles.*typedef struct*

*{*

*float x;*

*float y;*

*}CIRCLE;*

*CIRCLE circle;*

*void createcircle (int k, int r, int h) {*

*glBegin(GL_LINES);*

*for (int i = 0; i < 180; i++)*

*{*

*circle.x = r * cos(i) - h;*

*circle.y = r * sin(i) + k;*

*glVertex3f(circle.x + k,circle.y - h,0);*

*circle.x = r * cos(i + 0.1) - h;*

*circle.y = r * sin(i + 0.1) + k;*

*glVertex3f(circle.x + k,circle.y - h,0);*

*}*

*glEnd();*

*}*

If you know about the

**structures in C**then fine you understand the typedef else we have more object oriented approach**making use of classes for C++**. Same program above in classes.*class circle{*

*public : float x,y,rot;*

*public:*

*void createcircle (int k, int r, int h);*

*};*

*void circle::createcircle (int k, int r, int h) {*

*glBegin(GL_LINES);*

*for (int i = 0; i < 180; i++)*

*{*

*x = r * cos(i) - h;*

*y = r * sin(i) + k;*

*glVertex3f(x + k,y - h,0);*

*x = r * cos(i + 0.1) - h;*

*y = r * sin(i + 0.1) + k;*

*glVertex3f(x + k,y - h,0);*

*}*

*glEnd();*

*}*

ya sir i got it il just go through it if any modifications il let you know bt i have a another project same like a story as u heard of ant and bird an ant wil be stuckd in river it seeks help and bird helps it by dropping a leaf so in turn of exchange can i have any algorithm project using opengl

ReplyDeleteim not getting any algorithm sir

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ReplyDeleteof real appearance of animals

ReplyDeleteoffcourse i am trying to do that

ReplyDeleteok sir if you modify any real appearance of animals let me know and may i know that hanoi of tower program is been executed successfully

ReplyDeleteTower of Hanoi Project is working fine here in mysystem so do it will in your's

ReplyDeleterajeev sir i need source codw of algorithm if u have any algorithm suggest me

ReplyDeleterajeev sir i need a source code of any algorithm except lru sstf

ReplyDeletewhich algorithm there are many here

ReplyDeleteGudnght our lecturer said he wil give a topic algorithm tomorrow to do a mini project using opengl c++ so i will let you know the topic tomorrow

ReplyDeletehi rajeev sir do have any project based on freedom fighters like image of chitradurga fort and onaki obavva hits soldiers who come way hidden in forts of rocks and can say which project you have based on algorithm of os and any other as i am not gettng any idea about that rply me as soon you can get the message

ReplyDeleteIn visual c++ it is not giving output. its showing as 0 succeeded, 0 failed, 1 up-to-date,

ReplyDeletehow to get a output?

sir the speed of transfer of rings from 1 to 3 is very high...how to reduce the transfer speed

ReplyDeletesir rajeev sir kindly help me in mini project on algorithm

ReplyDeletecan i have any 3d project

ReplyDeletek fine i have shooting of objects in exchange can i have any 3d mini project using opengl

ReplyDeletethere are many algorithm projects in here

ReplyDeletewhy you not trying them or just mention one

can i have any 3d a wonderfull project

ReplyDeletefirst decide exactly what you want?

ReplyDeletei need one amazing worthy 3d mini project based on some tag line

ReplyDeletedo you have any idea as i have not much time

ReplyDeletehi rajeev sir actually i don hav any idea on 3d some of my friend doing 3d home with furnitured so if you have any3d projects let me knw

ReplyDeletehi rajeev sir am trying out from long days and texting you that can i have one wonderful and interesting cg project using c++ opengl if its cost also i have a some other projects can exchange it as i did it with hare and tortoise project with lru page replacement algorithm sourcecode

ReplyDeleteif it is 3d also no problem

ReplyDeleterajeev sir rply to my message let me know

ReplyDeletei am a bit busy with my work so not able to concentrate on the things........

ReplyDeletek sir fine but if you're free send me one interesting project if it cost i have source code of some wil exchange

ReplyDeletethe movement of the rings is too fast how to slow it

ReplyDeleteSir plz send me code link...available link is not working

ReplyDeleteDepolkarnikhil@gmail.com

ReplyDeleteCode link not working.Plz help Sir.tylorabcd@gmail.com

ReplyDeletesir is this hanoi project of using opengl functions

ReplyDeleteI have sent to you the mail with source cod links

ReplyDeletecheck your mail from openglprojects@gmail.com it has link for the hare tortoise projects

ReplyDeleteGet free project in exchange of any one that not published here

ReplyDeletesir i asked you for a algorithm sourcecode

ReplyDeletePls can I get source code for tower of Hanoi pls pls

ReplyDeletesource code for hare and the tortoise story

ReplyDelete