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coordinates

Started by utr0cks Jan 1, 2004 at 6:00 PM 1 replies 300+ views

Original Post

Jan 1, 2004 at 6:00 PM

ok, im making a little 2d game engine using textured quads in opengl. i translate my quads around using glTranslatef(x,y,-10) i always use -10 as my z coordinate i am having trouble figuring out which x, y pixels are visible at a depth of 10. I know about how many through trial and error, but there must be some formula that could tell me also... my gl window setup code is straight from nehe and looks like this...

glMatrixMode(GL_PROJECTION);						// Select The Projection Matrix
	glLoadIdentity();							// Reset The Projection Matrix

	// Calculate The Aspect Ratio Of The Window
	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	glMatrixMode(GL_MODELVIEW);						// Select The Modelview Matrix
	glLoadIdentity();							// Reset The Modelview Matrix
}

silvermace

105

silvermace

Jan 1, 2004 at 6:49 PM

a 2D game, i must ask why you are using perspective mode...
for 2d, use gluOrtho(...) with this each unit becomes a
pixel eg.


//alwayz 0 for z value in 2d mode
glTranslatef(10, 10, 0);
//translatefs 10 pixels right, and 10 pixels down

get it ?
if you need more help i can show you the code from my old 2d
shooter..

cu.
Irix

tHiSiSbOb

111

tHiSiSbOb

Jan 1, 2004 at 8:44 PM

quote:
Original post by silvermace
a 2D game, i must ask why you are using perspective mode...
for 2d, use gluOrtho(...) with this each unit becomes a
pixel eg.

//alwayz 0 for z value in 2d mode
glTranslatef(10, 10, 0);
//translatefs 10 pixels right, and 10 pixels down

get it ?
if you need more help i can show you the code from my old 2d
shooter..

cu.
Irix

Yea, if you are going to use GL for 2d stuff, you will want to use glOrtho. It just makes it easier to deal with screen coordinates than doing it any other way.

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