48 lines
1.5 KiB
C
48 lines
1.5 KiB
C
/*
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* trackball.h
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* A virtual trackball implementation
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* Written by Gavin Bell for Silicon Graphics, November 1988.
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*/
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/*
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* Pass the x and y coordinates of the last and current positions of
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* the mouse, scaled so they are from (-1.0 ... 1.0).
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*
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* if ox,oy is the window's center and sizex,sizey is its size, then
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* the proper transformation from screen coordinates (sc) to world
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* coordinates (wc) is:
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* wcx = (2.0 * (scx-ox)) / (float)sizex - 1.0
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* wcy = (2.0 * (scy-oy)) / (float)sizey - 1.0
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*
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* The resulting rotation is returned as a quaternion rotation in the
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* first paramater.
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*/
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void
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trackball(float q[4], float p1x, float p1y, float p2x, float p2y);
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/*
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* Given two quaternions, add them together to get a third quaternion.
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* Adding quaternions to get a compound rotation is analagous to adding
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* translations to get a compound translation. When incrementally
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* adding rotations, the first argument here should be the new
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* rotation, the second and third the total rotation (which will be
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* over-written with the resulting new total rotation).
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*/
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void
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add_quats(float *q1, float *q2, float *dest);
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/*
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* A useful function, builds a rotation matrix in Matrix based on
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* given quaternion.
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*/
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void
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build_rotmatrix(float m[4][4], float q[4]);
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/*
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* This function computes a quaternion based on an axis (defined by
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* the given vector) and an angle about which to rotate. The angle is
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* expressed in radians. The result is put into the third argument.
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*/
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void
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axis_to_quat(float a[3], float phi, float q[4]);
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