i'm trying to create my own User Interface such as: Button, panel, window, radiobutton, checkbox, etc..

the word "create" here means:

-designing UI with own style

-programming they all.

well, my problem is: what functions/codes that i must call to draw it all?

in this terms, maybe the points are:

-Drawing 2d texture on screen NOT in 3d world game.

so if we're doing translation camera in 3d world game, the UI texture won't be move.

-determine xy coordinates based on screen NOT based in 3d world game.

of course before we set UI texture first thing that we have to do is determine some textures.

to more cleary, take look at the picture

this is a sample User Interface that i've found in google. but this is XNA c#.

i've learned the source codes how they work. after i understood the concept (include how they draw many textures with structured coordinates)

ok so, the problem is: could you show me the point/codes that i should use in openGL graphic programming? include:

-Drawing 2d texture on screen NOT in 3d world game.

-determine xy coordinates in screen.

ok i got it.

here i got the things that must be understood before. there are some points to build User Interface in openGL.

• firstly, glOrtho help us to command "Orthographic Projection". although we're drawing 3d vertex no matter how far they are (in z coordinate). it will looks like 2D Image. but if we'd like to set our vertex Stay in front we should set z coordinate to 0.

ok, lets try my code that i've made.

 void DrawImage(void) 
{
	int width = window.width;  //your window width
	int height = window.height;//your window height
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0, width, height, 0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
// here you will set xy coordinate of vertex on our screen
glBegin(GL_QUADS);
//there are reason why z must be set to 0
glVertex3f(0, 0, 0.0);
glVertex3f(0, 0.5f, 0.0);
glVertex3f(-1.0f, 0.5f, 0.0);
glVertex3f(-1.0f, 0, 0.0);
glEnd();
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
}

• second, set up our input/output for Keyboard and Mouse. that's why it be called Graphic User Interface

Note that if you are using an orthographic projection that is windowwidth by windowheight in size, then drawing a quad as small as you are drawing will pretty much just draw a single pixel or two, since the viewport is now windowwidth units wide and windowheight units tall, and you are drawing a quad 1 unit wide and 1/2 unit tall. You need to draw your objects larger in order to see anything useful.

of course,, you've remind me.

when we build User Interface i think the best way to set the parameters of glOrtho like:

• left : 0.0f
• right: in accordance with our window width
• top: 0.0f
• bottom: in accordance with our window height
• Znear Zfar: 0,1 -> i don't know why is this so match with UI graphic (these values make the plane always on foreground of the vieweport)

there is a reason why do i set the right and the bottom in accordance with our window size. whenever we resize the window Coordinate of glOrtho won't be screwed.

do you remember in desktop application programming we're like drawing on Quadrant 4 (270 - 360 degree) but y coordinate it's just positive value NOT negative. therefore i set it up in accordance with desktop programming, it wold be easy!

well, for drawing vertex actually we have to adjust the coordinate also where the max x/y coordinate is in accordance with our window size. so if we would follow this way you must set your vertex like we're doing graphic programming on deskop programming. lets look at my vertex code:

::glTranslatef(0,0,0); //the position of the element
glBegin(GL_QUADS
//look actully we've created left sidebar
glVertex3f(200, 0, 0); 
glVertex3f(200, height, 0);
glVertex3f(0.0f, height, 0);
glVertex3f(0, 0, 0);
glEnd();

yeahh we've created a sidebar at viewport.

you see? x/y coordinate is set to large value (Something unusual). but in this term i've set before, with this command: glOrtho(0, window.width, window.height, 0, 0, 1);

the viewport will be fit to our window. even you resize your window size i think we're just build simple algorithm (something like anchor?) cz the viewport and the window are same!