From 5d39aa71dda9181e55417b48e6ffafabb0eb25ff Mon Sep 17 00:00:00 2001
From: clifford <clifford@b57f626f-c46c-0410-a088-ec61d464b74c>
Date: Fri, 22 Jan 2010 14:28:17 +0000
Subject: [PATCH] Clifford Wolf: 	Added spring() to example20 
 Improved generated linear_extrude + twist 3d grid

git-svn-id: http://svn.clifford.at/openscad/trunk@336 b57f626f-c46c-0410-a088-ec61d464b74c
---
 dxflinextrude.cc         | 68 +++++++++++++++++++++++++++++-----------
 dxftess-glu.cc           |  1 +
 examples/example020.scad | 37 ++++++++++++++++++++++
 3 files changed, 87 insertions(+), 19 deletions(-)

diff --git a/dxflinextrude.cc b/dxflinextrude.cc
index 7e0c2c6b..7a5b5883 100644
--- a/dxflinextrude.cc
+++ b/dxflinextrude.cc
@@ -144,26 +144,56 @@ static void add_slice(PolySet *ps, DxfData::Path *pt, double rot1, double rot2,
 		double kx2 = pt->points[k]->x *  cos(rot2*M_PI/180) + pt->points[k]->y * sin(rot2*M_PI/180);
 		double ky2 = pt->points[k]->x * -sin(rot2*M_PI/180) + pt->points[k]->y * cos(rot2*M_PI/180);
 
-		ps->append_poly();
-		if (pt->is_inner) {
-			ps->append_vertex(kx1, ky1, h1);
-			ps->append_vertex(jx1, jy1, h1);
-			ps->append_vertex(jx2, jy2, h2);
-		} else {
-			ps->insert_vertex(kx1, ky1, h1);
-			ps->insert_vertex(jx1, jy1, h1);
-			ps->insert_vertex(jx2, jy2, h2);
-		}
+		double dia1_len_sq = (jy1-ky2)*(jy1-ky2) + (jx1-kx2)*(jx1-kx2);
+		double dia2_len_sq = (jy2-ky1)*(jy2-ky1) + (jx2-kx1)*(jx2-kx1);
 
-		ps->append_poly();
-		if (pt->is_inner) {
-			ps->append_vertex(kx2, ky2, h2);
-			ps->append_vertex(kx1, ky1, h1);
-			ps->append_vertex(jx2, jy2, h2);
-		} else {
-			ps->insert_vertex(kx2, ky2, h2);
-			ps->insert_vertex(kx1, ky1, h1);
-			ps->insert_vertex(jx2, jy2, h2);
+		if (dia1_len_sq > dia2_len_sq)
+		{
+			ps->append_poly();
+			if (pt->is_inner) {
+				ps->append_vertex(kx1, ky1, h1);
+				ps->append_vertex(jx1, jy1, h1);
+				ps->append_vertex(jx2, jy2, h2);
+			} else {
+				ps->insert_vertex(kx1, ky1, h1);
+				ps->insert_vertex(jx1, jy1, h1);
+				ps->insert_vertex(jx2, jy2, h2);
+			}
+
+			ps->append_poly();
+			if (pt->is_inner) {
+				ps->append_vertex(kx2, ky2, h2);
+				ps->append_vertex(kx1, ky1, h1);
+				ps->append_vertex(jx2, jy2, h2);
+			} else {
+				ps->insert_vertex(kx2, ky2, h2);
+				ps->insert_vertex(kx1, ky1, h1);
+				ps->insert_vertex(jx2, jy2, h2);
+			}
+		}
+		else
+		{
+			ps->append_poly();
+			if (pt->is_inner) {
+				ps->append_vertex(kx1, ky1, h1);
+				ps->append_vertex(jx1, jy1, h1);
+				ps->append_vertex(kx2, ky2, h2);
+			} else {
+				ps->insert_vertex(kx1, ky1, h1);
+				ps->insert_vertex(jx1, jy1, h1);
+				ps->insert_vertex(kx2, ky2, h2);
+			}
+
+			ps->append_poly();
+			if (pt->is_inner) {
+				ps->append_vertex(jx2, jy2, h2);
+				ps->append_vertex(kx2, ky2, h2);
+				ps->append_vertex(jx1, jy1, h1);
+			} else {
+				ps->insert_vertex(jx2, jy2, h2);
+				ps->insert_vertex(kx2, ky2, h2);
+				ps->insert_vertex(jx1, jy1, h1);
+			}
 		}
 	}
 }
diff --git a/dxftess-glu.cc b/dxftess-glu.cc
index 57eb7041..9e5f5308 100644
--- a/dxftess-glu.cc
+++ b/dxftess-glu.cc
@@ -95,6 +95,7 @@ static void STDCALL tess_end(void)
 
 static void STDCALL tess_error(GLenum errno)
 {
+	fprintf(stderr, "GLU tesselation error %s", gluErrorString(errno));
 	PRINTF("GLU tesselation error %s", gluErrorString(errno));
 }
 
diff --git a/examples/example020.scad b/examples/example020.scad
index 83229399..e008f0bc 100644
--- a/examples/example020.scad
+++ b/examples/example020.scad
@@ -32,8 +32,45 @@ module nut(type = 2, r1 = 16, r2 = 21, r3 = 30, s = 6, n = 7, h = 100/5, t = 8/5
 	}
 }
 
+module spring(r1 = 100, r2 = 10, h = 100, hr = 12)
+{
+	stepsize = 1/16;
+	module segment(i1, i2) {
+		alpha1 = i1 * 360*r2/hr;
+		alpha2 = i2 * 360*r2/hr;
+		len1 = sin(acos(i1*2-1))*r2;
+		len2 = sin(acos(i2*2-1))*r2;
+		if (len1 < 0.01)
+			polygon([
+				[ cos(alpha1)*r1, sin(alpha1)*r1 ],
+				[ cos(alpha2)*(r1-len2), sin(alpha2)*(r1-len2) ],
+				[ cos(alpha2)*(r1+len2), sin(alpha2)*(r1+len2) ]
+			]);
+		if (len2 < 0.01)
+			polygon([
+				[ cos(alpha1)*(r1+len1), sin(alpha1)*(r1+len1) ],
+				[ cos(alpha1)*(r1-len1), sin(alpha1)*(r1-len1) ],
+				[ cos(alpha2)*r1, sin(alpha2)*r1 ],
+			]);
+		if (len1 >= 0.01 && len2 >= 0.01)
+			polygon([
+				[ cos(alpha1)*(r1+len1), sin(alpha1)*(r1+len1) ],
+				[ cos(alpha1)*(r1-len1), sin(alpha1)*(r1-len1) ],
+				[ cos(alpha2)*(r1-len2), sin(alpha2)*(r1-len2) ],
+				[ cos(alpha2)*(r1+len2), sin(alpha2)*(r1+len2) ]
+			]);
+	}
+	linear_extrude(height = 100, twist = 180*h/hr,
+			$fn = (hr/r2)/stepsize, convexity = 5) {
+		for (i = [ stepsize : stepsize : 1+stepsize/2 ])
+			segment(i-stepsize, min(i, 1));
+	}
+}
+
 translate([ -30, 0, 0 ])
 screw();
 
 translate([ 30, 0, 0 ])
 nut();
+
+spring();