StackOverflow2013

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POgluLookAt trouble
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copied!<p>I have some code which draws a line along the x, y and z axes. My problem is that these lines are being clipped so that they are invisible near the origin:</p> <p><img src="https://i.stack.imgur.com/ubm26.png" alt="clipped axes"></p> <p>This sounds like a far clipping plane issue, but I gave zFar=50 to gluPerspective, which should be plenty. Making it even larger doesn't seem to help. What else could be causing the clipping?</p> <p>Here is my code:</p> <pre><code>import static org.lwjgl.opengl.GL11.*; import org.lwjgl.opengl.*; import org.lwjgl.util.glu.GLU; public class Test { static int width = 300, height = 200; public static void main(String[] _) throws Exception { Display.setDisplayMode(new DisplayMode(width, height)); Display.create(); glClear(GL_COLOR_BUFFER_BIT); // projection matrix glMatrixMode(GL_PROJECTION_MATRIX); glLoadIdentity(); GLU.gluPerspective(50, width / (float) height, .1f, 50); // modelview matrix glMatrixMode(GL_MODELVIEW); glLoadIdentity(); GLU.gluLookAt( .8f, .8f, .8f, 0, 0, 0, 0, 1, 0); // draw a line for each axis glBegin(GL_LINES); // x axis in red glColor3f(1, 0, 0); glVertex3i(0, 0, 0); glVertex3i(10, 0, 0); // y axis in green glColor3f(0, 1, 0); glVertex3i(0, 0, 0); glVertex3i(0, 10, 0); // z axis in blue glColor3f(0, 0, 1); glVertex3i(0, 0, 0); glVertex3i(0, 0, 10); glEnd(); Display.update(); // wait for a close event while (!Display.isCloseRequested()) { Thread.sleep(20); Display.processMessages(); } Display.destroy(); } } </code></pre> <p><strong>Update</strong> - Removing <code>glLoadIdentity();</code> after <code>glMatrixMode(GL_MODELVIEW);</code> gives the desired result, but I don't understand why. Isn't the default modelview matrix the identity matrix?</p> <p><strong>Update</strong> - I wrote a C version of the same code and it works as desired. Why the difference?</p>

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