glOrtho appears to have no effect - opengl

Question

I was drawing a square with coordinates (-.5, -.5), (-.5, .5), (.5, .5), (.5, -.5) and I noticed that it appeared squashed in my 800 x 600 window (which seems entirely logical).
I was trying to fix it so that the square appeared square, not rectangular. My approach was to call glOrtho() with values of left = -ar, right = ar, bottom = -1, top = 1 where ar was my aspect ratio (800/600). What I found was that any call I made to glOrtho() had no effect, including the one I was already making (I could remove it and nothing would change).
My understanding of glOrtho() is that it maps the corners of the OpenGL context to the values supplied, and stretches everything between those points to fit. Is that incorrect, or am I doing something that's preventing my call to glOrtho() from taking effect?
import org.lwjgl.BufferUtils;
import org.lwjgl.LWJGLException;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import java.nio.FloatBuffer;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL15.*;
public class GLOrthoTestDriver {
public static void main(String[] args) {
try {
Display.setDisplayMode(new DisplayMode(800, 600));
Display.setTitle("glOrtho Test");
Display.create();
} catch (LWJGLException e) {
e.printStackTrace();
Display.destroy();
System.exit(1);
}
// Initialization code for OpenGL
glMatrixMode(GL_PROJECTION);
glOrtho(-1, 1, -1, 1, -1, 1);
glLoadIdentity();
// Scene setup
int vertexBufferHandle;
int colorBufferHandle;
FloatBuffer vertexData = BufferUtils.createFloatBuffer(8);
vertexData.put(new float[]
{
-.5f, -.5f,
-.5f, .5f,
.5f, .5f,
.5f, -.5f
}
);
vertexData.flip();
FloatBuffer colorData = BufferUtils.createFloatBuffer(12);
colorData.put(new float[]
{
1, 1, 1,
1, 1, 1,
1, 1, 1,
1, 1, 1
}
);
colorData.flip();
vertexBufferHandle = glGenBuffers();
colorBufferHandle = glGenBuffers();
glBindBuffer(GL_ARRAY_BUFFER, vertexBufferHandle);
glBufferData(GL_ARRAY_BUFFER, vertexData, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, colorBufferHandle);
glBufferData(GL_ARRAY_BUFFER, colorData, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
while (!Display.isCloseRequested()) {
glClear(GL_COLOR_BUFFER_BIT);
glBindBuffer(GL_ARRAY_BUFFER, vertexBufferHandle);
glVertexPointer(2, GL_FLOAT, 0, 0);
glBindBuffer(GL_ARRAY_BUFFER, colorBufferHandle);
glColorPointer(3, GL_FLOAT, 0, 0);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glDrawArrays(GL_QUADS, 0, 4);
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
Display.update();
Display.sync(60);
}
glDeleteBuffers(vertexBufferHandle);
glDeleteBuffers(colorBufferHandle);
Display.destroy();
}
}

Answer 1

Ah - your problem is that you're calling glLoadIdentity after calling glOrtho. glLoadIdentity replaces the matrix in the current mode (GL_PROJECTION) with the identity matrix, thus wiping out any previous call to glOrtho.
Try calling glLoadIdentity before glOrtho.