Hi, I have a seemingly basic problem that I can''t quite figure out as I''m a newbie I have a model in the centre of my view which I wish to rotate using keys/mouse. I therefore need to turn a 2d delta/move into a 3d rotation. I have tried example code from books and can rotate my model nicely but the effect is non-intuitive. As my model moves its rotation axis moves with it rather than being relative to the 2d screen. For example if I rotate my model forward 90 degrees then my old y axis is now the z axis and the z axis is now the y axis. The effect I want is if the user now presses the rotate right key the rotation should now be a rotation around the z axis not the y axis. I can not use conditional logic as the angles will obviously be arbitary and not just 90 degrees. Here is some example code : LRESULT CGLView::OnKeyDown(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled) { UINT nChar = wParam; UINT nRepCnt = HIWORD(lParam); UINT nFlags = LOWORD(lParam); switch(nChar) { case VK_UP: { m_xRot-= 5.0f; if(m_xRot < -1.0f) { m_xRot = 355.0f; } } break; case VK_DOWN: { m_xRot += 5.0f; if(m_xRot > 356.0f) { m_xRot = 0.0f; } } break; case VK_LEFT: { m_yRot -= 5.0f; if(m_yRot < -1.0f) { m_yRot = 355.0f; } } break; case VK_RIGHT: { m_yRot += 5.0f; if(m_yRot > 356.0f) { m_yRot = 0.0f; } } break; } InvalidateRect(NULL); UpdateWindow(); return 0; } void CGLView::RenderScene(HDC hDC, HGLRC& hRC) { wglMakeCurrent(hDC, hRC); // Clear the color and depth buffers glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Save the matrix state and do the rotations glMatrixMode(GL_MODELVIEW); glLoadIdentity(); // Allow lighting polygon shading ... // Position light ... // Translate the whole scene out and into view glTranslatef(0.0f, 0.0f, -400.0f); // Perform user view rotations, (in degrees) glRotatef(static_cast(m_xRot), 1.0f, 0.0f, 0.0f); glRotatef(static_cast(m_yRot), 0.0f, 1.0f, 0.0f); // glRotatef(static_cast(m_zRot), 0.0f, 0.0f, 1.0f); RenderModel(); glLoadIdentity(); // Finish up glFlush(); } Thanks David Marsh

There is a very crude way do do this, but it''s not very nice. You have to remove the glLoadIdentity() at the beginning of your draw code, as well as the 3 viewer rotation. Also, put a glRotatef function under the keys. eg:

case VK_UP
{
glRotatef(-5.0f, 1.0f, 0.0f, 0.0f);
}

This way, the rotations will just keep accumulating and since you don''t clear it, the model will rotate as you want it. around the current position rather than the models position.

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