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PODefining and Manipulating a 3D Object with Specific Rotations
 

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  1. PODefining and Manipulating a 3D Object with Specific Rotations
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    <p>I have rendered a very rough model of a molecule that consists of 7 helices and would like to ask if there is anyway possible to allow the helices themselves to tilt (rotate) in certain ways so as to interact with one another. For clarity, I insert an image of my program output (although for an orthographic projection, so it appears as the projection of a 3D helix onto a 2D plane). </p> <p><img src="https://i.stack.imgur.com/bfaXs.jpg" alt="enter image description here"></p> <p>I have included the code for rending a single helix (all others are the same). </p> <p>Would it be useful to store the geometry of my objects in vertex arrays instead of rendering them each time separately for the 7 different colors? (Each helix consists of 36,000 vertices and I am concerned that the arrays might get large enough to cause serious performance issues?)</p> <p>I understand the matrix stack is the data structure for performing multiple consecutive individual transformations on particular objects, but I not sure how exactly to specify so that an entire one of my helices can tilt? (glRotatef does not actually tilt the helices for some reason) </p> <pre><code>/*HELIX RENDERING*/ glLoadIdentity(); glMatrixMode(GL_MODELVIEW); glPushMatrix(); glTranslatef(0.0, 100.0, -5.0); //Move Position glRotatef(90.0, 0.0, 0.0, 0.0); glBegin(GL_LINE_STRIP); for(theta = 0.0; theta &lt;= 360.0; theta += 0.01) { x = r*(cosf(theta)); y = r*(sinf(theta)); z = c*theta; glVertex3f(x,y,z); glColor3f(1.0, 1.0, 0.0); } glEnd(); glPopMatrix(); </code></pre>
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    1. COYou might be (very) interested by glDisplayList : http://www.songho.ca/opengl/gl_displaylist.html
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    2. COAlso, glRotatef(90.0, 0.0, 0.0, 0.0); is rotating x,y,z by 0.0*90 ;) try glRotatef(90.0, 1.0, 0.0, 0.0); to rotate x by 90
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    3. CO@Williwaw Thanks for the advice, glRotate(90.0f,1.0f,1.0f,0.0) seems to be roughly the type of affine transformation I was aiming for. I considered using a display list in my program but for rendering only seven helices it seems somewhat unnecessary to burden the memory since the graphics card will take care of most rendering commands.
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