heebie

[vg.git] / vg_lines.h

diff --git a/vg_lines.h b/vg_lines.h
index 12e8d969f6df17005a084fe101ee699a9e5092c9..9300445a8b35dc21816a76571ba10256e7d55cdd 100644 (file)
--- a/vg_lines.h
+++ b/vg_lines.h
@@ -178,6 +178,41 @@ VG_STATIC void vg_line( line_co from, line_co to, u32 colour )
        vg_line2( from, to, colour, colour );
 }
 
+VG_STATIC void line_tangent_basis( v3f n, v3f tx, v3f ty )
+{
+   /* Compute tangent basis (box2d) */
+   if( fabsf( n[0] ) >= 0.57735027f )
+   {
+      tx[0] =  n[1];
+      tx[1] = -n[0];
+      tx[2] =  0.0f;
+   }
+   else
+   {
+      tx[0] =  0.0f;
+      tx[1] =  n[2];
+      tx[2] = -n[1];
+   }
+
+   v3_normalize( tx );
+   v3_cross( n, tx, ty );
+}
+
+VG_STATIC void vg_line_arrow( line_co co, line_co dir, float size, u32 colour )
+{
+   v3f p1, tx, ty, p2, p3;
+   v3_muladds( co, dir, size, p1 );
+   line_tangent_basis( dir, tx, ty );
+
+   v3_muladds( p1, dir, -size * 0.125f, p2 );
+   v3_muladds( p2, ty,  size * 0.125f, p3 );
+   v3_muladds( p2, ty, -size * 0.125f, p2 );
+
+   vg_line( co, p1, colour );
+   vg_line( p1, p2, colour );
+   vg_line( p1, p3, colour );
+}
+
 VG_STATIC void vg_line_boxf( boxf box, u32 colour )
 {
    v3f p000, p001, p010, p011, p100, p101, p110, p111;