The LineStripArray

The LineStripArray primitive expands on the basic LineArray by allowing you to describe a collection of lines that form a continuous item without needing to repeat vertices in the provided coordinate collection. If you take a look back at Figure 4, you'll notice that, in order to have a continuous line, the shared vertex had to be declared twice - as vertices 3 and 8 in the array of coordinates. With a LineStripArray, that problem is eliminated.

To do this, the LineStripArray (and all of the other strip-based primitives) introduces another piece of required data - the length of a strip. A strip is how many coordinates to link together in a single primitive that use shared vertices. In the non-strip primitives, the coordinate vertices were read out of the array directly. Each group was read sequentially in a multiple according to the primitive type (line, point, triangle etc). The strip-based geometry now uses an extra variable to tell the renderer how many of those coordinates should be linked together to form a single line, before starting the next line.

Construction

    int format = GeometryArray.COORDINATE |
                 GeometryArray.COLOR_3;

	int[] strip_counts = { 3 };

    LineStripArray lines = new LineStripArray(8, format, strip_counts);

Figure 9: A line strip array showing the vertex numbering for a single strip of 3 vertices

    float[] vertices =
    {
        0,   0,  0,   // v1
        0,   2,  0,   // v2
        1,   5, -3,   // v3
    };

    lines.setCoordinates(0, vertices);