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matrix: Add cogl_matrix_look_at
Similar to the widely used gluLookAt API, this adds a CoglMatrix utility for setting up a view transform in terms of positioning a camera/eye position that points to a given object position aligned to a given world-up vector. Reviewed-by: Neil Roberts <neil@linux.intel.com>
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@ -2051,3 +2051,65 @@ cogl_matrix_is_identity (const CoglMatrix *matrix)
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else
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else
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return memcmp (matrix, identity, sizeof (float) * 16) == 0;
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return memcmp (matrix, identity, sizeof (float) * 16) == 0;
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}
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}
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void
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cogl_matrix_look_at (CoglMatrix *matrix,
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float eye_position_x,
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float eye_position_y,
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float eye_position_z,
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float object_x,
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float object_y,
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float object_z,
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float world_up_x,
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float world_up_y,
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float world_up_z)
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{
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CoglMatrix tmp;
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CoglVector3 forward;
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CoglVector3 side;
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CoglVector3 up;
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/* Get a unit viewing direction vector */
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cogl_vector3_init (&forward,
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object_x - eye_position_x,
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object_y - eye_position_y,
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object_z - eye_position_z);
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cogl_vector3_normalize (&forward);
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cogl_vector3_init (&up, world_up_x, world_up_y, world_up_z);
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/* Take the sideways direction as being perpendicular to the viewing
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* direction and the word up vector. */
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cogl_vector3_cross_product (&side, &forward, &up);
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cogl_vector3_normalize (&side);
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/* Now we have unit sideways and forward-direction vectors calculate
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* a new mutually perpendicular up vector. */
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cogl_vector3_cross_product (&up, &side, &forward);
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tmp.xx = side.x;
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tmp.yx = side.y;
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tmp.zx = side.z;
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tmp.wx = 0;
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tmp.xy = up.x;
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tmp.yy = up.y;
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tmp.zy = up.z;
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tmp.wy = 0;
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tmp.xz = -forward.x;
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tmp.yz = -forward.y;
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tmp.zz = -forward.z;
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tmp.wz = 0;
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tmp.xw = 0;
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tmp.yw = 0;
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tmp.zw = 0;
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tmp.ww = 1;
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cogl_matrix_translate (&tmp, -eye_position_x, -eye_position_y, -eye_position_z);
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tmp.flags = (MAT_FLAG_GENERAL_3D | MAT_DIRTY_TYPE | MAT_DIRTY_INVERSE);
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cogl_matrix_multiply (matrix, matrix, &tmp);
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}
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@ -193,6 +193,62 @@ cogl_matrix_scale (CoglMatrix *matrix,
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float sy,
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float sy,
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float sz);
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float sz);
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#define cogl_matrix_look_at cogl_matrix_look_at_EXP
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/**
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* cogl_matrix_look_at:
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* @matrix: A 4x4 transformation matrix
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* @eye_position_x: The X coordinate to look from
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* @eye_position_y: The Y coordinate to look from
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* @eye_position_z: The Z coordinate to look from
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* @object_x: The X coordinate of the object to look at
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* @object_y: The Y coordinate of the object to look at
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* @object_z: The Z coordinate of the object to look at
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* @world_up_x: The X component of the world's up direction vector
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* @world_up_y: The Y component of the world's up direction vector
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* @world_up_z: The Z component of the world's up direction vector
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*
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* Applies a view transform @matrix that positions the camera at
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* the coordinate (@eye_position_x, @eye_position_y, @eye_position_z)
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* looking towards an object at the coordinate (@object_x, @object_y,
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* @object_z). The top of the camera is aligned to the given world up
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* vector, which is normally simply (0, 1, 0) to map up to the
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* positive direction of the y axis.
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*
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* Because there is a lot of missleading documentation online for
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* gluLookAt regarding the up vector we want to try and be a bit
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* clearer here.
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*
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* The up vector should simply be relative to your world coordinates
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* and does not need to change as you move the eye and object
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* positions. Many online sources may claim that the up vector needs
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* to be perpendicular to the vector between the eye and object
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* position (partly because the man page is somewhat missleading) but
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* that is not necessary for this function.
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*
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* <note>You should never look directly along the world-up
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* vector.</note>
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*
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* <note>It is assumed you are using a typical projection matrix where
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* your origin maps to the center of your viewport.</note>
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*
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* <note>Almost always when you use this function it should be the first
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* transform applied to a new modelview transform</note>
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*
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* Since: 1.8
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* Stability: unstable
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*/
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void
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cogl_matrix_look_at (CoglMatrix *matrix,
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float eye_position_x,
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float eye_position_y,
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float eye_position_z,
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float object_x,
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float object_y,
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float object_z,
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float world_up_x,
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float world_up_y,
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float world_up_z);
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/**
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/**
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* cogl_matrix_frustum:
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* cogl_matrix_frustum:
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* @matrix: A 4x4 transformation matrix
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* @matrix: A 4x4 transformation matrix
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@ -424,6 +424,7 @@ cogl_matrix_free
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cogl_matrix_frustum
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cogl_matrix_frustum
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cogl_matrix_ortho
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cogl_matrix_ortho
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cogl_matrix_perspective
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cogl_matrix_perspective
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cogl_matrix_look_at
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cogl_matrix_multiply
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cogl_matrix_multiply
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cogl_matrix_rotate
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cogl_matrix_rotate
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cogl_matrix_translate
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cogl_matrix_translate
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