The triangulation of Opengl ES line

This paper mainly discusses the algorithm to extend the line into 2d line surface.

It's easy to extend the P0P1 line into a polygon.

vec2f line = P1-p0

vec2f normal = vec2f (-line.y, line.x). Normalized () .

vec2f A = p0-thickness * normal;vec2f B = p0 + thickness * normal;vec2f c = p1-thickness * normal;vec2f d = p1 + thickness * normal;

If this is a straight line, but if there is a polyline, we also need to calculate the intersection point where

First we'll find out t
vec2fT= ((P2-P1). Normalized () + (P1-P0). normalized ()). Normalized ()
The second is to find out M
vec2f m = vec2f (-T. Y,T. x)
And finally find out the length of D.
float D = Thickness/miter.dot (normal)

You can get all the vertices you want based on the above, and then build triangular patches from those vertices

Roughly as follows:

void Trianglepolyline (const vec2f &p0, const vec2f &AMP;P1, const vec2f &AMP;P2, const vec2f &AMP;P3, Posarray & <span style= "font-family: ' Courier New ', Courier, Monospace;"                >mesh</span>) {if (P1 = = p2) return;                vec2f line = (P2-P1). normalize (); vec2f normal = vec2f (-line. Y, line.                X). normalize (); vec2f Tangent1 = (P0 = = p1)?        Line: ((p1-p0). Normalize () + line). Normalize (); vec2f Tangent2 = (P2 = = p3)?                Line: ((P3-P2). Normalize () + line). Normalize (); vec2f miter1 = vec2f (-tangent1. Y, Tangent1.        X); vec2f miter2 = vec2f (-tangent2. Y, Tangent2.                        X);        float length1 = radius/normal.dotproduct (miter1);                float length2 = radius/normal.dotproduct (Miter2);            if (true) {PUSH (p1-length1 * miter1);            PUSH (P2-LENGTH2 * miter2);            PUSH (p1 + length1 * miter1);        PUSH (p2 + length2 * miter2); }    }

The calling code is as follows

  for (int i = 0;i<vertexes.size (); ++i) {                int a = ((I-1) < 0)? 0: (i-1);                int b = i;                int c = ((i+1) >= vertexes.size ())? Vertexes.size ()-1: (i+1);                int d = ((i+2) >= vertexes.size ())? Vertexes.size ()-1: (i+2);                                Trianglepolyline (Vertexes[a], vertexes[b], vertexes[c], Vertexis[d],<span style= "font-family: ' Courier New ', Courier, Monospace; " >mesh</span>);            }

Vertexes saysPolyline , mesh represents the constructed vertex array number of spoke groups directly drawn with Gl_lines
The effect is roughly as follows


Please note that the above process is relatively small at the angle of the two-segment lineThere will be problems, all please use with caution .

The triangulation of Opengl ES line