From dd80c82747d0610de5aef87f2e43d510aaca7d68 Mon Sep 17 00:00:00 2001
From: Stuart Buchanan <stuart_d_buchanan@yahoo.co.uk>
Date: Wed, 27 Jan 2021 20:05:49 +0000
Subject: [PATCH] WS30:  Property configuration VPB

Configure the VPB elevation mesh via properties:
/scenery/elevation-mesh/sample-ratio controls the elevation
mesh sampling, allowing reduction in mesh size

/scenery/elevation-mesh/vertical-scale is just for fun and
scales the mesh vertically making mountains taller.

/scenery/elevation-mesh/constraint-gap-m controls how much below
airports etc. elevation vertices are forced to be.
---
 defaults.xml              |  5 +++
 gui/dialogs/rendering.xml | 70 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/defaults.xml b/defaults.xml
index f154915a6..f99437f42 100644
--- a/defaults.xml
+++ b/defaults.xml
@@ -1325,6 +1325,11 @@ Started September 2000 by David Megginson, david@megginson.com
     <share-events type="bool" userarchive="y">false</share-events>
     <events type="string"/>
     <use-vpb type="bool">false</use-vpb>
+    <elevation-mesh>
+      <sample-ratio type="float" userarchive="y">1.0</sample-ratio>
+      <vertical-scale type="float" userarchive="y">1.0</vertical-scale>
+      <constraint-gap-m type="float" userarchive="y">1.0</constraint-gap-m>
+    </elevation-mesh>
   </scenery>
   <earthview>
     <cloudsphere-flag type="bool" userarchive="y">true</cloudsphere-flag>
diff --git a/gui/dialogs/rendering.xml b/gui/dialogs/rendering.xml
index 7deb64310..8915fba33 100644
--- a/gui/dialogs/rendering.xml
+++ b/gui/dialogs/rendering.xml
@@ -181,7 +181,7 @@
 				<layout>hbox</layout>
 				<halign>left</halign>
 				<text>
-					<label>Maximum number of aircraft and scenery tiles</label>
+					<label>Maximum number of aircraft and scenery tiles cached</label>
 				</text>
 				<slider>
 					<name>max-plod</name>
@@ -218,6 +218,72 @@
 				</visible>
 			</text>
 
+			<group>
+				<layout>hbox</layout>
+				<halign>right</halign>
+				<visible>
+					<equals>
+						<property>/scenery/use-vpb</property>
+						<value>true</value>
+					</equals>
+				</visible>
+
+				<text>
+					<label>Elevation mesh sampling ratio</label>
+				</text>
+				<slider>
+					<name>elev-sample</name>
+					<min>0.05</min>
+					<max>1.0</max>
+					<step>0.05</step>
+					<fraction>0.17</fraction>
+					<property>/scenery/elevation-mesh/sample-ratio</property>
+					<binding>
+						<command>dialog-apply</command>
+						<object-name>elev-sample</object-name>
+					</binding>
+				</slider>
+				<text>
+					<label>1234</label>
+					<format>%.2f</format>
+					<live>true</live>
+					<property>/scenery/elevation-mesh/sample-ratio</property>
+				</text>
+			</group>
+
+			<group>
+				<layout>hbox</layout>
+				<halign>right</halign>
+				<visible>
+					<equals>
+						<property>/scenery/use-vpb</property>
+						<value>true</value>
+					</equals>
+				</visible>
+
+				<text>
+					<label>Elevation delta below airports</label>
+				</text>
+				<slider>
+					<name>elev-delta</name>
+					<min>0.0</min>
+					<max>20.0</max>
+					<step>1.0</step>
+					<fraction>0.17</fraction>
+					<property>/scenery/elevation-mesh/constraint-gap-m</property>
+					<binding>
+						<command>dialog-apply</command>
+						<object-name>elev-delta</object-name>
+					</binding>
+				</slider>
+				<text>
+					<label>1234</label>
+					<format>%2dm</format>
+					<live>true</live>
+					<property>/scenery/elevation-mesh/constraint-gap-m</property>
+				</text>
+			</group>
+
 			<empty>
 				<stretch>1</stretch>
 			</empty>
@@ -1091,6 +1157,8 @@
 				"/sim/rendering/vegetation-density",
 				"/sim/rendering/clouds3d-enable",
 				"/sim/rendering/clouds3d-density",
+				"/scenery/elevation-mesh/sample-ratio",
+				"/scenery/elevation-mesh/constraint-gap-m",
 				"/sim/rendering/scenery-path-suffix[0]/enabled",
 				"/sim/rendering/scenery-path-suffix[1]/enabled",
 				"/sim/rendering/scenery-path-suffix[2]/enabled",