bgnqstrip, endqstrip - delimit the vertices of a quadrilateral strip
Vertices specified between bgnqstrip and endqstrip are used to define a
strip of quadrilaterals. The graphics pipe maintains three vertex
registers. The first, second, and third vertices are loaded into the
registers, but no quadrilateral is drawn until the system executes the
fourth vertex routine. Upon executing the fourth vertex routine, the
system draws a quadrilateral through the vertices, then replaces the two
oldest vertices with the third and fourth vertices.
For each new pair of vertex routines, the system draws a quadrilateral
through two new vertices and the two older stored vertices, then replaces
the older stored vertices with the two new vertices.
The quadrilaterals are drawn as though each quadrilateral was an
independent polygon with vertex order (n, n+1, n+3, n+2).
If the quadrilateral projects a self-intersecting polygon, its rendering
will be hardware-specific. The Graphics Library only guarantees that
pixels outside of the convex hull will not be modified.
Between bgnqstrip and endqstrip you can issue the following Graphics
Library routines: c, color, cpack, lmbind, lmcolor, lmdef, n, RGBcolor,
t, and v. Use lmdef and lmbind only to respecify materials and their
There is no limit to the number of vertices that can be specified between
bgnqstrip and endqstrip. The result is undefined, however, if an odd
number of vertices are specified, or if fewer than four vertices are
By default, quadrilateral vertices are forced to the nearest pixel center
prior to scan conversion. Quadrilateral accuracy is improved when this
coercion is defeated with the subpixel command. Subpixel vertex
positioning is especially important when quadrilaterals are scan
converted with antialiasing enabled (see polysmooth).
After endqstrip, the current graphics position is undefined.
See the Graphics Library Programmer's Guide for examples.
backface, c, concave, frontface, polymode, polysmooth, scrsubdivide,
defpattern, shademodel, subpixel, v
IRIS-4D VGX models use vertex normals to improve the shading quality of
quadrilaterals, regardless of whether lighting is enabled.
On some systems quadrilateral strips are decomposed into triangles prior
to shading and scan conversion.
See the section, "2.1.4 Polygons," in the Graphics Library Programmer's
Guide for a discussion on the handling of non-coplanar and/or selfintersecting
See the section, "2.1.6 Meshes," in the Graphics Library Programmer's
Guide for a discussion on the order of the vertices when a q-strip is
decomposed into its equivalent t-mesh.
On Impact and Infinite Reality lmcolor cannot be called between bgnqstrip
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