From a19011b730ac6d770e3b42cde3a10961495a417d Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 20 Jan 2024 20:10:12 +0000
Subject: Implement basic network curve part shader

---
 gfx/gl/shaders/networkCurve.gs | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

(limited to 'gfx/gl/shaders/networkCurve.gs')

diff --git a/gfx/gl/shaders/networkCurve.gs b/gfx/gl/shaders/networkCurve.gs
index c504df3..82d8c59 100644
--- a/gfx/gl/shaders/networkCurve.gs
+++ b/gfx/gl/shaders/networkCurve.gs
@@ -4,6 +4,8 @@ flat in ivec3 apos[];
 flat in ivec3 bpos[];
 flat in ivec3 cpos[];
 flat in float reps[];
+flat in float aangle[];
+flat in float bangle[];
 
 layout(points) in;
 layout(triangle_strip, max_vertices = 255) out;
@@ -12,8 +14,33 @@ const mat2 rot = mat2(1);
 
 include(`networkCommon.glsl')
 
+mat2
+getRot(float angle)
+{
+	return mat2(cos(angle), sin(angle), -sin(angle), cos(angle));
+}
+
 void
 main()
 {
-	doSeg(0, apos[0], bpos[0], 0.f, reps[0], rot, rot);
+	float segs = floor(255 / (profile.length() * 2));
+	float radius = distance(cpos[0], apos[0]);
+	vec3 arcstep = vec3((bangle[0] - aangle[0]), // angle
+						   reps[0], // texture
+						   (bpos[0].z - apos[0].z)) // height
+			/ segs;
+
+	ivec3 prevPos = apos[0];
+	mat2 prevRot = getRot(aangle[0]);
+	float prevTex = 0;
+	for (vec3 arc = arcstep; arc.y < reps[0] - 0.01; arc += arcstep) {
+		mat2 rot = getRot(arc.x + aangle[0]);
+		ivec3 pos = cpos[0] + ivec3(rot * vec2(radius, 0), arc.z);
+		float tex = arc.y;
+		doSeg(segDist(prevPos, pos), pos, prevPos, tex, prevTex, rot, prevRot);
+		prevPos = pos;
+		prevRot = rot;
+		prevTex = tex;
+	}
+	doSeg(segDist(prevPos, bpos[0]), bpos[0], prevPos, reps[0], prevTex, getRot(bangle[0]), prevRot);
 }
-- 
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