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  1. PO
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    <p>Your above code really doesn't do anything that would be visible because you don't render anything after altering the currently active matrix. The effect of the following code segment is as follows (assume the current stack is <code>MODELVIEW</code>):</p> <pre><code>glPushMatrix(); // push the stack down one matrix and copy the current matrix glRotatef(90,1,0,0); // multiply the current matrix M by a rotation matrix R -&gt; M' = M * R // usually you would render stuff here using the current model-view matrix glPopMatrix(); // pop the top matrix off the stack </code></pre> <p>As you can see, by pushing a new matrix onto the stack, you preserve what ever matrix was on top before the push. Then you manipulate the current top matrix in some way, render stuff, and pop the top matrix off to restore the previous state.</p> <p>I think you can see now why your above code does absolutely nothing of essence - except cause unnecessary overhead.</p> <p>Using the matrix stack, if you insist on using legacy GL, is generally correct here, because you don't want your modifications affecting subsequently rendered geometry. However, what you really want is simple matrix concatenation. Assuming you want to perform and <em>extrinsic rotation</em>, i.e. a rotation about the fixed basis of <code>world-space</code> in <code>z-y-x</code>, you need to do the following:</p> <pre><code>glPushMatrix(); glRotatef(90,1,0,0); glRotatef(90,0,1,0); glRotatef(90,0,0,1); // render camera glPopMatrix(); </code></pre> <p>The above is mathematically equivalent to calculation a rotation matrix <code>R</code> by concatenating the individual rotations <code>R_z</code>, <code>R_y</code> and <code>R_x</code>: <code>R' = R_x * R_y * R_z</code>.</p> <p>I suggest you also read <a href="http://en.wikipedia.org/wiki/Euler_angles" rel="nofollow">this</a> and to better understand what you're doing and potential problems with rotations in general.</p>
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    1. PORoatating an Object around its (x,y&z) axis contemporaneously in C++ using OpenGL
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    1. USthokra
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      1. VTAcceptedByOriginator
    1. COthank u for your answer; but I tested this code and also there is nothing in output:(
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      1. USGolnaz Saraji
    2. COok I understand my wrong; before rendering the camera I pop the matrix and so I could not see the rotation in output; thank you so much!
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      1. USGolnaz Saraji
 

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