From 15dba6ef35cde494411c7d58f9e19f0104b39707 Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Sat, 11 Oct 2008 10:00:25 +0000
Subject: [PATCH] added slope image

---
 panda/src/grutil/geoMipTerrain.cxx | 38 ++++++++++++++++++++++++++----
 panda/src/grutil/geoMipTerrain.h   |  1 +
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/panda/src/grutil/geoMipTerrain.cxx b/panda/src/grutil/geoMipTerrain.cxx
index 25c083d4b1..6264daa449 100644
--- a/panda/src/grutil/geoMipTerrain.cxx
+++ b/panda/src/grutil/geoMipTerrain.cxx
@@ -292,10 +292,10 @@ get_elevation(double x, double y) {
 //               accurate normals, please divide it by the
 //               terrain scale and normalize it again, like this:
 //
-//               LVector3f normal (terr.get_normal(mx, my, x, y));
-//               normal.set(normal.get_x() / terr.get_sx(),
-//                          normal.get_y() / terr.get_sy(),
-//                          normal.get_z() / terr.get_sz());
+//               LVector3f normal (terr.get_normal(x, y));
+//               normal.set(normal.get_x() / root.get_sx(),
+//                          normal.get_y() / root.get_sy(),
+//                          normal.get_z() / root.get_sz());
 //               normal.normalize();
 ////////////////////////////////////////////////////////////////////
 LVector3f GeoMipTerrain::
@@ -316,6 +316,36 @@ get_normal(int x, int y) {
   return normal;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: GeoMipTerrain::make_slope_image
+//       Access: Published
+//  Description: Returns a new grayscale image containing the slope
+//               angles. A pixel value of 1.0 will mean 90 degrees,
+//               meaning, horizontal, a pixel value of 0.0 will
+//               mean 0 degrees, or entirely vertical.
+//               The resulting image will have the same size as the
+//               heightfield image.
+//               The scale will be taken into respect -- meaning,
+//               if you change the terrain scale, the slope image
+//               will need to be regenerated in order to be correct.
+////////////////////////////////////////////////////////////////////
+PNMImage GeoMipTerrain::
+make_slope_image() {
+  PNMImage result (_xsize, _ysize);
+  result.make_grayscale();
+  for (int x = 0; x < _xsize; ++x) {
+    for (int y = 0; y < _ysize; ++y) {
+      LVector3f normal (get_normal(x, y));
+      normal.set(normal.get_x() / _root.get_sx(),
+                 normal.get_y() / _root.get_sy(),
+                 normal.get_z() / _root.get_sz());
+      normal.normalize();
+      result.set_gray(x, y, normal.angle_deg(LVector3f::up()) / 90.0);
+    }
+  }
+  return result;
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: GeoMipTerrain::generate
 //       Access: Published
diff --git a/panda/src/grutil/geoMipTerrain.h b/panda/src/grutil/geoMipTerrain.h
index 97a715f844..3b92174dfd 100644
--- a/panda/src/grutil/geoMipTerrain.h
+++ b/panda/src/grutil/geoMipTerrain.h
@@ -105,6 +105,7 @@ PUBLISHED:
                                             unsigned short my);
   INLINE LVecBase2f get_block_from_pos(double x, double y);
   
+  PNMImage make_slope_image();
   void generate();
   bool update();