ffffggggllllSSSSeeeelllleeeeccccttttBBBBuuuuffffffffeeeerrrr has two arguments: _b_u_f_f_e_r is a pointer to an array of
unsigned integers, and _s_i_z_e indicates the size of the array. _b_u_f_f_e_r
returns values from the name stack (see ffffggggllllIIIInnnniiiittttNNNNaaaammmmeeeessss, ffffggggllllLLLLooooaaaaddddNNNNaaaammmmeeee,
ffffggggllllPPPPuuuusssshhhhNNNNaaaammmmeeee) when the rendering mode is GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTT (see ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee).
ffffggggllllSSSSeeeelllleeeeccccttttBBBBuuuuffffffffeeeerrrr must be issued before selection mode is enabled, and it
must not be issued while the rendering mode is GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTT.
A programmer can use selection to determine which primitives are drawn
into some region of a window. The region is defined by the current
modelview and perspective matrices.
In selection mode, no pixel fragments are produced from rasterization.
Instead, if a primitive or a raster position intersects the clipping
volume defined by the viewing frustum and the user-defined clipping
planes, this primitive causes a selection hit. (With polygons, no hit
occurs if the polygon is culled.) When a change is made to the name
stack, or when ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee is called, a hit record is copied to _b_u_f_f_e_r
if any hits have occurred since the last such event (name stack change or
ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee call). The hit record consists of the number of names in
the name stack at the time of the event, followed by the minimum and
maximum depth values of all vertices that hit since the previous event,
followed by the name stack contents, bottom name first.
Depth values (which are in the range [0,1]) are multiplied by 2^32 - 1,
before being placed in the hit record.
An internal index into _b_u_f_f_e_r is reset to 0 whenever selection mode is
entered. Each time a hit record is copied into _b_u_f_f_e_r, the index is
incremented to point to the cell just past the end of the block of names
- that is, to the next available cell. If the hit record is larger than
the number of remaining locations in _b_u_f_f_e_r, as much data as can fit is
copied, and the overflow flag is set. If the name stack is empty when a
hit record is copied, that record consists of 0 followed by the minimum
To exit selection mode, call ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee with an argument other than
GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTT. Whenever ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee is called while the render mode is
GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTT, it returns the number of hit records copied to _b_u_f_f_e_r, resets
the overflow flag and the selection buffer pointer, and initializes the
name stack to be empty. If the overflow bit was set when ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee
was called, a negative hit record count is returned.
NNNNOOOOTTTTEEEESSSS
The contents of _b_u_f_f_e_r is undefined until ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee is called with an
argument other than GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTT.
ffffggggllllBBBBeeeeggggiiiinnnn/ffffggggllllEEEEnnnndddd primitives and calls to ffffggggllllRRRRaaaasssstttteeeerrrrPPPPoooossss can result in hits.
EEEERRRRRRRROOOORRRRSSSS
GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____VVVVAAAALLLLUUUUEEEE is generated if _s_i_z_e is negative.
GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____OOOOPPPPEEEERRRRAAAATTTTIIIIOOOONNNN is generated if ffffggggllllSSSSeeeelllleeeeccccttttBBBBuuuuffffffffeeeerrrr is called while the
render mode is GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTT, or if ffffggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee is called with argument
GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTT before ffffggggllllSSSSeeeelllleeeeccccttttBBBBuuuuffffffffeeeerrrr is called at least once.
GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____OOOOPPPPEEEERRRRAAAATTTTIIIIOOOONNNN is generated if ffffggggllllSSSSeeeelllleeeeccccttttBBBBuuuuffffffffeeeerrrr is executed between
the execution of ffffggggllllBBBBeeeeggggiiiinnnn and the corresponding execution of ffffggggllllEEEEnnnndddd.
ffffggggllllGGGGeeeetttt with argument GGGGLLLL____NNNNAAAAMMMMEEEE____SSSSTTTTAAAACCCCKKKK____DDDDEEEEPPPPTTTTHHHH
ffffggggllllGGGGeeeetttt with argument GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTTIIIIOOOONNNN____BBBBUUUUFFFFFFFFEEEERRRR____SSSSIIIIZZZZEEEE
ffffggggllllGGGGeeeettttPPPPooooiiiinnnntttteeeerrrrvvvv with argument GGGGLLLL____SSSSEEEELLLLEEEECCCCTTTTIIIIOOOONNNN____BBBBUUUUFFFFFFFFEEEERRRR____PPPPOOOOIIIINNNNTTTTEEEERRRR
