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POSetting a orthographic projection matrix?
 

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  1. POSetting a orthographic projection matrix?
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    <p>I am having trouble setting a orthographical projection matrix of dimensions 4x2 with (0,0) being in the center, (-2, -1) being at the bottom left corner, and (2, 1) being at the top right corner.</p> <p>I use <code>glutInitWindowSize(600, 300);</code> to initialize the window size. In my reshape function, I use <code>glViewport(0, 0, w, h);</code> to set the viewport. Also in my reshape function, I use <code>gluOrtho2D(-(float)w/h, (float)w/h, -2.0, 2.0);</code> to set the ortho.</p> <p>However, when I move my mouse around to see the world coordinates, the bottom left corner is (-1, -1) and the top right corner is (1, 1). Is there something I am doing wrong here? I am assuming since I am setting bottom and top to -2 and 2 respectively in the gluOrtho2D call, it should give me the right coordinates.</p> <p>Please help me out if you see anything that might be wrong.</p> <p>Here is my code so far, please ignore the arm variables and drawing functions.</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;math.h&gt; #include &lt;stdlib.h&gt; #include &lt;iostream&gt; #if 0 /*unix*/ #include &lt;GL/glut.h&gt; #endif #if 1 /*apple */ #include &lt;GLUT/glut.h&gt; #include &lt;OPENGL/gl.h&gt; #include &lt;OPENGL/glext.h&gt; #endif #if 0 /*windows*/ #include &lt;io.h&gt; #include &lt;fcntl.h&gt; #include &lt;glut.h&gt; #endif int GW, GH; bool animfore, animupper; float foreangle, upperangle; using namespace std; void drawShoulder(); void drawUpper(); void drawFore(); void display() { glClear(GL_COLOR_BUFFER_BIT); glLoadIdentity(); //draw shoulder glPushMatrix(); drawShoulder(); //draw upper arm glPushMatrix(); drawUpper(); //draw forearm glPushMatrix(); drawFore(); glPopMatrix(); glPopMatrix(); glPopMatrix(); glutPostRedisplay(); glutSwapBuffers(); } void drawShoulder() { //cout &lt;&lt; "Enters" &lt;&lt; endl; glBegin(GL_POLYGON); glColor3f((float)30/255, (float)0/255, (float)30/255); glVertex2f(-2.0, -0.4); glVertex2f(-2.0, -1.0); glVertex2f(-1.0, -1.0); glVertex2f(-1.0, -0.4); glEnd(); } void drawUpper() { } void drawFore() { } void reshape(GLsizei w, GLsizei h) { GW = w; GW = h; glViewport(0, 0, w, h); glLoadIdentity(); gluOrtho2D(-(float)w/h, (float)w/h, -1.0, 1.0); cout &lt;&lt; "Enters" &lt;&lt; endl; } void keyboard(unsigned char key, int x, int y) { switch(key) { case 'q' : case 'Q' : exit(EXIT_SUCCESS); break; } } //control arm animations void idle() { if(animupper) { } if(animfore) { } } float p2w_x(int gx) { return (float)2.*GW/(GW*GH-GH)*gx-(float)GW/GH; } float p2w_y(int gy) { int py = GH-1-gy; return (float)2./(GH-1.)*py-1; } void mouseMove(int x, int y) { cout &lt;&lt; "(" &lt;&lt; p2w_x(x) &lt;&lt; "," &lt;&lt; p2w_y(y) &lt;&lt; ")" &lt;&lt; endl; } int main(int argc, char **argv) { // global variable intializations GW = 600; GH = 300; animfore, animupper = true; glutInit(&amp;argc, argv); glutInitDisplayMode(GLUT_DOUBLE); // initialization glutInitWindowSize(600, 300); glutInitWindowPosition(100, 100); glutCreateWindow("Robot Arm"); glClearColor(1.0, 1.0, 1.0, 1.0); // callback functions glutDisplayFunc(display); glutKeyboardFunc(keyboard); glutReshapeFunc(reshape); glutIdleFunc(idle); glutMotionFunc(mouseMove); glutMainLoop(); } </code></pre>
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