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/networkCommon.glsl | 45 ++++++++++++++++++++++-----------------
 gfx/gl/shaders/networkCurve.gs    | 29 ++++++++++++++++++++++++-
 gfx/gl/shaders/networkCurve.vs    |  6 ++++++
 gfx/gl/shaders/networkStraight.vs |  6 +++---
 4 files changed, 63 insertions(+), 23 deletions(-)

(limited to 'gfx/gl/shaders')

diff --git a/gfx/gl/shaders/networkCommon.glsl b/gfx/gl/shaders/networkCommon.glsl
index 2639eb1..e1811bc 100644
--- a/gfx/gl/shaders/networkCommon.glsl
+++ b/gfx/gl/shaders/networkCommon.glsl
@@ -16,26 +16,33 @@ uniform float flatDistance = 1000000;
 out vec2 texCoord;
 out vec3 rposition;
 
-void
-doVertex(const ivec3 end, const int v, const float texY, const mat2 rot)
+float
+segDist(const ivec3 a, const ivec3 b)
 {
-	rposition = vec3(rot * profile[v].xy, profile[v].z);
-	ivec3 vpos = end + ivec3(rposition);
-	gl_Position = viewProjection * vec4(vpos - viewPoint, 1);
-	texCoord = vec2(texturePos[v], texY);
-	EmitVertex();
+	return min(distance(viewPoint, a), distance(viewPoint, b));
 }
 
-void
-doSeg(const float dist, const ivec3 apos, const ivec3 bpos, const float atexY, const float btexY, const mat2 arot,
-		const mat2 brot)
-{
-	if (dist < clipDistance) {
-		int vstep = (dist < flatDistance) ? 1 : profile.length() - 1;
-		for (int v = 0; v < profile.length(); v += vstep) {
-			doVertex(bpos, v, btexY, brot);
-			doVertex(apos, v, atexY, arot);
+ifelse(
+		TYPE, .gs,
+		// Begin: Geometry shader only function
+		void doVertex(const ivec3 end, const int v, const float texY, const mat2 rot) {
+			rposition = vec3(rot * profile[v].xy, profile[v].z);
+			ivec3 vpos = end + ivec3(rposition);
+			gl_Position = viewProjection * vec4(vpos - viewPoint, 1);
+			texCoord = vec2(texturePos[v], texY);
+			EmitVertex();
 		}
-		EndPrimitive();
-	}
-}
+
+		void doSeg(const float dist, const ivec3 apos, const ivec3 bpos, const float atexY, const float btexY,
+				const mat2 arot, const mat2 brot) {
+			if (dist < clipDistance) {
+				int vstep = (dist < flatDistance) ? 1 : profile.length() - 1;
+				for (int v = 0; v < profile.length(); v += vstep) {
+					doVertex(bpos, v, btexY, brot);
+					doVertex(apos, v, atexY, arot);
+				}
+				EndPrimitive();
+			}
+		}
+		// End: Geometry shader only function
+)
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);
 }
diff --git a/gfx/gl/shaders/networkCurve.vs b/gfx/gl/shaders/networkCurve.vs
index d083765..6c56e93 100644
--- a/gfx/gl/shaders/networkCurve.vs
+++ b/gfx/gl/shaders/networkCurve.vs
@@ -4,11 +4,15 @@ layout(location = 0) in ivec3 v_apos;
 layout(location = 1) in ivec3 v_bpos;
 layout(location = 2) in ivec3 v_centre;
 layout(location = 3) in float v_reps;
+layout(location = 4) in float v_aangle;
+layout(location = 5) in float v_bangle;
 
 flat out ivec3 apos;
 flat out ivec3 bpos;
 flat out ivec3 cpos;
 flat out float reps;
+flat out float aangle;
+flat out float bangle;
 
 void
 main()
@@ -17,4 +21,6 @@ main()
 	bpos = v_bpos;
 	cpos = v_centre;
 	reps = v_reps;
+	aangle = v_aangle;
+	bangle = v_bangle;
 }
diff --git a/gfx/gl/shaders/networkStraight.vs b/gfx/gl/shaders/networkStraight.vs
index a0fa437..55f9c4f 100644
--- a/gfx/gl/shaders/networkStraight.vs
+++ b/gfx/gl/shaders/networkStraight.vs
@@ -5,14 +5,14 @@ layout(location = 1) in ivec3 v_bpos;
 layout(location = 2) in mat2 v_rot;
 layout(location = 4) in float v_reps;
 
-uniform ivec3 viewPoint;
-
 flat out ivec3 apos;
 flat out ivec3 bpos;
 flat out mat2 rot;
 flat out float reps;
 flat out float dist;
 
+include(`networkCommon.glsl')
+
 void
 main()
 {
@@ -20,5 +20,5 @@ main()
 	bpos = v_bpos;
 	rot = v_rot;
 	reps = v_reps;
-	dist = min(distance(viewPoint, v_apos), distance(viewPoint, v_bpos));
+	dist = segDist(v_apos, v_bpos);
 }
-- 
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