I'm using/targetting OpenGL 4.20, GSLSL 4.20, core. Using C.

I'm exploring graphics with OpenGL and have decided to make a tile based game. I'm at the point where i'd like to actually draw a bunch of tiles, and am trying to use glDrawElements to draw individual triangles.

Relevant code:

const float vertexPositions[] = {
  -1.0f, -0.8f, //0
  -0.8f, -0.8f, //1
  -0.6f, -0.8f, //2
  -0.4f, -0.8f, //3
  -0.2f, -0.8f, //4
   0.0f, -0.8f, //5

  -1.0f, -1.0f, //6
  -0.8f, -1.0f, //7
  -0.6f, -1.0f, //8
  -0.4f, -1.0f, //9
  -0.2f, -1.0f, //10
   0.0f, -1.0f, //11

//The following are the texture coordinates.
  0.00f, 1.00f,
  1.00f, 1.00f,
  0.00f, 1.00f,
  1.00f, 1.00f,
  0.00f, 1.00f,
  1.00f, 1.00f,

  0.00f, 0.00f,
  1.00f, 0.00f,
  0.00f, 0.00f,
  1.00f, 0.00f,
  0.00f, 0.00f,
  1.00f, 0.00f,
};

const GLubyte indices[] = {
  0, 1, 6, 
  1, 7, 6, 
  1, 2, 7, 
  2, 8, 7, 
  2, 3, 8, 
  3, 9, 8,
  3, 4, 9,
  4, 10, 9,
  4, 5, 10,
  5, 11, 10,
};

with

glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void *)96);

glDrawElements(GL_TRIANGLES, 30, GL_UNSIGNED_BYTE, indices);

(There are other pieces, but it's mostly formatting/attribute enabling etc. I'll provide more if needed).

Basically what i get is:

0  1  2  3  4  5
+--+--+--+--+--+
|b | d|b |d |b |
+--+--+--+--+--+
6  7  8  9 10 11

and what i want is:

0  1  2  3  4  5
+--+--+--+--+--+
|b |b |b |b |b |
+--+--+--+--+--+
6  7  8  9 10 11

Where "b" is the correct orientation of the texture/square and "d" is the reverse/reflected.

I realize that since the vertex coordinates are shared this is going to happen, but from my own thoughts/some posts below it seems like it is unavoidable. Either I conserve vertices and have reflected textures, or I end up sending 3*2*number_of_tiles vertices, which i fe

c opengl textures
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