Window-to-viewport mapping

[appel]

I'm going nuts over this, but I'm studying OpenGL, and this book I have isn't doing a good job explaining this to me.

All I need actually is verification, I know how to do this mapping, but I just need to know what actually happens!

Little definition first;

(this is a 2D scenario)

World = Everything in the game, based on X,Y cartesian axes.

World-Window = What part of the World is being displayed from P1=(x1,y1) through P2=(x2,y2).

Viewport = Defines how the World-Window is displayed.


Everything in the world-window gets stretched to fit whatever size viewport is defined as.

I made a image:



Am I correct about this?

[appel]

Kevglass verified to me that I am correct.

But, I'm trying to accomplish this in lwjgl.

What I'm doing is;

drawing a polygon (rectangle) that is 10x10, and has the origin point 0,0.

I have defined:
GL11.glOrtho(0, 10, 0, 10, -1, 1);
GL11.glViewport(0,640,0,480);

Shouldn't that polygon fill the window? (the window is 640x480).

Nothing happens :\


my code is here: http://www.private.is/arni/OpenGL.java

[Fool Running]

One thing you might try, is to do GL_QUADS or GL_TRIANGLES instead of GL_POLYGON.
Also its possible that the polygon you are drawing is getting culled (not drawn because its facing the wrong way). Try drawing the polygon in the reverse order. I can't remember if OpenGL defaults to clockwise or counter-clockwise front face.

[appel]

Kevglass gave me the solution;

GL11.glViewport(0,0,640,480);
GL11.glMatrixMode(GL11.GL_PROJECTION);					
GL11.glLoadIdentity();						
GL11.glOrtho(0, 10, 10, 0, -1, 1);		
GL11.glMatrixMode(GL11.GL_MODELVIEW);		
GL11.glLoadIdentity();