Document part of the vertex positions generated here

Encountered as I made a failed attempt at solving the issue with rendering transparent support. I tried to order vertices appropriately but failed miserably.

plugins/SimulationView/layers3d.shader

@@ -202,17 +202,17 @@ geometry41core =
         }
         size_y = v_line_dim[1].y / 2 + 0.01;
 
-        g_vertex_delta = gl_in[1].gl_Position - gl_in[0].gl_Position;
-        g_vertex_normal_horz_head = normalize(vec3(-g_vertex_delta.x, -g_vertex_delta.y, -g_vertex_delta.z));
-        g_vertex_offset_horz_head = vec4(g_vertex_normal_horz_head * size_x, 0.0);
+        g_vertex_delta = gl_in[1].gl_Position - gl_in[0].gl_Position; //Actual movement exhibited by the line.
+        g_vertex_normal_horz_head = normalize(vec3(-g_vertex_delta.x, -g_vertex_delta.y, -g_vertex_delta.z)); //Lengthwise normal vector pointing backwards.
+        g_vertex_offset_horz_head = vec4(g_vertex_normal_horz_head * size_x, 0.0); //Lengthwise offset vector pointing backwards.
 
-        g_vertex_normal_horz = normalize(vec3(g_vertex_delta.z, g_vertex_delta.y, -g_vertex_delta.x));
+        g_vertex_normal_horz = normalize(vec3(g_vertex_delta.z, g_vertex_delta.y, -g_vertex_delta.x)); //Normal vector pointing right.
+        g_vertex_offset_horz = vec4(g_vertex_normal_horz * size_x, 0.0); //Offset vector pointing right.
 
-        g_vertex_offset_horz = vec4(g_vertex_normal_horz * size_x, 0.0); //size * g_vertex_normal_horz;
-        g_vertex_normal_vert = vec3(0.0, 1.0, 0.0);
-        g_vertex_offset_vert = vec4(g_vertex_normal_vert * size_y, 0.0);
+        g_vertex_normal_vert = vec3(0.0, 1.0, 0.0); //Upwards normal vector.
+        g_vertex_offset_vert = vec4(g_vertex_normal_vert * size_y, 0.0); //Upwards offset vector. Goes up by half the layer thickness.
 
-        if ((v_line_type[0] == 8) || (v_line_type[0] == 9)) {
+        if ((v_line_type[0] == 8) || (v_line_type[0] == 9)) { //Travel or retraction moves.
             vec4 va_head = viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_horz_head + g_vertex_offset_vert);
             vec4 va_up =  viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_horz + g_vertex_offset_vert);
             vec4 va_down = viewProjectionMatrix * (gl_in[0].gl_Position - g_vertex_offset_horz + g_vertex_offset_vert);
@@ -238,16 +238,16 @@ geometry41core =
 
             EndPrimitive();
         } else {
-            vec4 va_m_horz = viewProjectionMatrix * (gl_in[0].gl_Position - g_vertex_offset_horz);
-            vec4 vb_m_horz = viewProjectionMatrix * (gl_in[1].gl_Position - g_vertex_offset_horz);
-            vec4 va_p_vert = viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_vert);
-            vec4 vb_p_vert = viewProjectionMatrix * (gl_in[1].gl_Position + g_vertex_offset_vert);
-            vec4 va_p_horz = viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_horz);
-            vec4 vb_p_horz = viewProjectionMatrix * (gl_in[1].gl_Position + g_vertex_offset_horz);
-            vec4 va_m_vert = viewProjectionMatrix * (gl_in[0].gl_Position - g_vertex_offset_vert);
-            vec4 vb_m_vert = viewProjectionMatrix * (gl_in[1].gl_Position - g_vertex_offset_vert);
-            vec4 va_head   = viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_horz_head);
-            vec4 vb_head   = viewProjectionMatrix * (gl_in[1].gl_Position - g_vertex_offset_horz_head);
+            vec4 va_m_horz = viewProjectionMatrix * (gl_in[0].gl_Position - g_vertex_offset_horz); //Line start, left vertex.
+            vec4 vb_m_horz = viewProjectionMatrix * (gl_in[1].gl_Position - g_vertex_offset_horz); //Line end, left vertex.
+            vec4 va_p_vert = viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_vert); //Line start, top vertex.
+            vec4 vb_p_vert = viewProjectionMatrix * (gl_in[1].gl_Position + g_vertex_offset_vert); //Line end, top vertex.
+            vec4 va_p_horz = viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_horz); //Line start, right vertex.
+            vec4 vb_p_horz = viewProjectionMatrix * (gl_in[1].gl_Position + g_vertex_offset_horz); //Line end, right vertex.
+            vec4 va_m_vert = viewProjectionMatrix * (gl_in[0].gl_Position - g_vertex_offset_vert); //Line start, bottom vertex.
+            vec4 vb_m_vert = viewProjectionMatrix * (gl_in[1].gl_Position - g_vertex_offset_vert); //Line end, bottom vertex.
+            vec4 va_head   = viewProjectionMatrix * (gl_in[0].gl_Position + g_vertex_offset_horz_head); //Line start, tip.
+            vec4 vb_head   = viewProjectionMatrix * (gl_in[1].gl_Position - g_vertex_offset_horz_head); //Line end, tip.
 
             // All normal lines are rendered as 3d tubes.
             myEmitVertex(v_vertex[0], v_color[0], -g_vertex_normal_horz, va_m_horz);