View Full Version : vertex reading color how to

07-13-2003, 04:07 AM
Hi opengl people!! thank you fisrt of all for ur interess in my question.
I will try to be more understandable.
I have a cursor that i can move on a window of opengl. That cursor draw a red path along the way he "walk". My problem is that i want to make impossible for the "player" to move the cursor on a path segment he still "walked", like it was a wall. Now i m understanding i have to recognize where the wall is. My question is can i read from the colour of the pixel in the window if there is a wall or not. In few words i would like to read the colour of a pixel in the opengl window without save in a array each pixel i have drawn before. I know there is a buffer as the depth buffer from where u can read the information of a pixel with a function (i think glReadPixel but i didnt it before and the tutorials i did read are too difficult for me. If u were so gently to wrote me a little example that were beautifull!!!
I would need something like
colorofxypixel = glreadthecolorofxypixel

but i dont know how to dooooo
i use glut and opengl libraries i did study a little c and c++ but not win32 or such things like mfc and co...
(my target were to program a little wolfied game because in that i have i cannot save my play....)
So thank u all and good programming day!!

07-13-2003, 05:29 PM
(a) This is a beginner question and not appropriate for this forum.

(b) Do a search on the web for glReadPixel and you'll find all the information you need on how to use it.

07-13-2003, 10:52 PM
dear rgpcfogkals i have to learn something to you!
In the past i have always thunk that beginners doesnt need very eccellent material or professors because they dont need 100% of precision, they are only beginners...
But now that i ma a little older i can surely tell you that that was a wrong idea i had!
If a beginner learn from a beginner and he does all the thing with 60-80% precision, after a couple of years it will be impossible for him to really return at the perfect methodology of work he wanted at the start from professionally professors. I simply dont want to get stupid habit. But now i did see wath for a technician are u....
That is stupid you wirte to me an answer (i was so happy there was one...) in wich u tell me u are profi and i m only a ****... so uselessy... U are sure profi with opengl but please try to be more modest in your life!!!

07-14-2003, 02:02 AM
So beginners should ask noob questions in the advanced forum and those interested in advanced topics should put up with stupid little gits with faulty keyboards?

07-14-2003, 05:23 AM
i excuse me for my mistakes but i would like to invite you to write italian like i write english.... it could be interessant and funny!
Ehi boy u are a V.I.P. but i dont understand why do u have time to answer such dummy question then.... leave me to my life and i will leave to yours! I did ask something u and only you wanted to answer. If u dont want to answer to beginners then go ahead but dont tell me wath i have to do in a free place such this. ok! bye and i hope never to ear of you

07-14-2003, 05:32 AM
You are asking about this?

The man pages are at

All the functions should be there.