Trapezoid specification with spans?

Hi Keith,

Just looking over the render protocol spec. I notice that the
trapezoid is specified there as two spans, each with a left, right,
and y fixed-point value.

The specification also requires left to be less than right for each
span, (which would eliminate the problematic intersection within a
pixel, but might make it harder to use trapezoids for all triangles).

>From our discussion it seems that you've already changed your mind in
favor of a trapezoid representation using two y values and four
arbitrary points, (which then makes it easier to share lines across
multiple polygons).

So I am thinking of:

typedef struct {
    xPointFixed	p1;
    xPointFixed	p2;
} xLineFixed;

typedef struct {
    Fixed       top;
    Fixed       bottom;
    xLineFixed	left;
    xLineFixed	right;
} xTrap;

Seem reasonable enough?

-Carl

-- 
Carl Worth                                        
USC Information Sciences Institute                 [email protected]
3811 N. Fairfax Dr. #200, Arlington VA 22203		  703-812-3725