How can I use OpenGL directly in minecraft to draw a GUI?

[ManicMonkey]

Basically the title. I only need to draw in 2D. I know about GuiScreen and how to make a Gui with a Container, all that stuff. I just wanted to take a step forward and make a sort of Gui Framework offering a set of components and a layout manager. So one of my questions is, can I draw triangles??? Like this:

 

glBegin(GL_TRIANGLE_STRIP);
//vertices here
glEnd();

 

I ask because the game is all made of quads, apparently, and I needed triangles for my GUI, so maybe there's some limitation to the OpenGL environment?

 

Can I have a very simple example? I also don't know how to transform the coordinate system correctly before drawing the GUI, if the example could include that, it would be really appreciated.

 

(edit summary: typo)

[Ernio]

https://en.wikibooks.org/wiki/OpenGL_Programming/GLStart/Tut3

 

Minecraft has a wrapper on GL that server you with "nice" (depends) vertex format that has ability to make nice texturing/colorizing/stuff.

 

Anyway - when talking about GUIs - MC uses id=7 (look 1st link: GL_QUADS).

All vertex formats that are shape (meaning non-line like GL_LINES) are expected to be drawn ANTI-CLOCKWISE.

 

Mentioned "wrapper" for basic GL is (was) called Tesselator and currently all operations are in WorldRenderer (Tesselator.getInstance().getWorldRenderer()).

 

All possible examples are placed in Gui.class (and few others).

 

And yes - any other GL operations are possible/allowed during usage of WorldRenderer or not (it is really just a wrapper).

 

EDIT

 

"I also don't know how to transform the coordinate system correctly"

 

I have no clue what you mean. top/left screen is 0/0. You just take some x/y and draw your stuff. Scaling is done automatically - depenging on GUISize - I am talking about that thing you can set in game options "large", "medium", "small", etc. , AND window scaling.

There are cases where you might need manual scaling - this can be taken from ScaledResolution (lookup callbacks of this class - gives you direct examples).

[ManicMonkey]

Thanks! Good to know I can draw anything. About the coordinate system, based on what you said it seems minecraft already transforms it for us when drawing a GUI then, which is also very good to know. Thanks for the reply!

[ManicMonkey]

Oh, just one more thing. The wrapper you told me about, you know what OpenGL version it uses? (equal to or greater than 3.1?)

[coolAlias]

Last I checked it was 2.9, but you should be able to find out by looking at your project's referenced libraries.

[ManicMonkey]

Thank you.