2D Coordinate Confusion - opengl

Question

Alright, so I have never created a game before, and I am trying to make a 2d tile based game.
So I am really confused about something that should be pretty simple, coordinates.
I have tile coordinates, like
{0,0,0,0,0,1}
{0,0,1,0,0,1}
{0,0,0,0,0,1}
{0,0,1,1,1,1}
{0,0,0,0,0,1}
lets say this is my world and i am trying to render it, well i cant render it, each tile needs a width,
this is where i get confused, so you can do, im not new to coding
twidth = 100, theight = 100;
for(y = each row) {
for(x = each tile in each row) {
draw rect (
X1 = x*twidth,
Y1 = y*theight,
X2 = x*twidth+twidth,
X2 = y*theight+theight
)
}
}
I might be wrong about this, but: now literally everything else needs to multiplied by the twidth/height, it will be even harder if you want different sized tiles, at least its confusing to me, how do other games handle things like this? im not sure if i explained very well what my problem is, any help would be appreciated
im using opengl[legacy] and i think the solution might be a function to setup screenspace differently, so rendering
glVertex2d(0,1) is actually 100px, this would make collisions, and such, much easier

Answer 1

im using opengl[legacy] and i think the solution might be a function to setup screenspace differently, so rendering glVertex2d(0,1) is actually 100px, this would make collisions, and such, much easier
You can achieve that in legacy OpenGL by setting up the projection matrix properly:
glMatrixMode(GL_PROJECTION);
glOrtho(0, 16, 0, 9, -1, 1);
This will set it up so that glVertex2d(0, 0) maps to the bottom left corner and glVertex2d(16, 9) will map to the top right corner, giving you 16x9 tiles in the viewport. To fix the size of the tile in pixels we calculate the fractional number of tiles instead:
glOrtho(0, (double)viewportWidth / twidth, 0, (double)viewportHeight / theight, -1, 1);
After that you can 'scroll' the world by translating it through the GL_MODELVIEW matrix.