Squashed commit of the following: (closes #85)

commit cff663ad0e23ed73057201fc0c71f12de82be201
Author: wolfgangp <[email protected]>
Date:   Thu Mar 10 10:48:39 2016 +0100

    Make get_normal_world_on_b return a vector.

commit 6fe5f5a24d615dc05b532c07486e23123e4cc9f2
Author: wolfgangp <[email protected]>
Date:   Thu Mar 3 00:30:01 2016 +0100

    Remove comments.

commit f94f0ebd1acde2c3c32ffdaadd24deb4d16d1a84
Author: wolfgangp <[email protected]>
Date:   Wed Mar 2 23:53:05 2016 +0100

    Revert header author change.

commit d50c41b830034e2dc015298cd4596b6292d582ac
Author: wolfgangp <[email protected]>
Date:   Wed Mar 2 23:38:45 2016 +0100

    Fix indentation and spaces.

commit 792eab5fe1ca77564a36d7ab43b8996e03432dbd
Author: wolfgangp <[email protected]>
Date:   Wed Mar 2 20:11:43 2016 +0100

    Revert changed date.

commit 99f78d4a90d43cf3cc5e5168c319020b307cdbd0
Author: wolfgangp <[email protected]>
Date:   Wed Mar 2 19:01:39 2016 +0100

    Fix bulletHeightfieldShape to support non-square images. Add alternative constructor taking a Texture input, intended for use with ShaderTerrainMesh.

panda/src/bullet/bulletHeightfieldShape.cxx

@@ -16,7 +16,9 @@
 TypeHandle BulletHeightfieldShape::_type_handle;
 
 /**
- *
+ * @brief Creates a collision shape suited for terrains from a rectangular image.
+ * @details Stores the image's brightness values in a vector Bullet can use, 
+ *   while rotating it 90 degrees to the right.
  */
 BulletHeightfieldShape::
 BulletHeightfieldShape(const PNMImage &image, PN_stdfloat max_height, BulletUpAxis up) {
@@ -28,8 +30,10 @@ BulletHeightfieldShape(const PNMImage &image, PN_stdfloat max_height, BulletUpAx
 
   for (int row=0; row < _num_rows; row++) {
     for (int column=0; column < _num_cols; column++) {
-      _data[_num_cols * row + column] =
-        max_height * image.get_bright(column, _num_cols - row - 1);
+      // Transpose
+      _data[_num_rows * column + row] =
+        // Flip y
+        max_height * image.get_bright(row, _num_cols - column - 1);
     }
   }
 
@@ -59,3 +63,41 @@ set_use_diamond_subdivision(bool flag) {
 
   return _shape->setUseDiamondSubdivision(flag);
 }
+
+/**
+ * @brief Creates a collision shape suited for terrains from a rectangular texture.
+ * @details Alternative constructor intended for use with ShaderTerrainMesh. This will
+ *   do bilinear sampling at the corners of all texels. Also works with textures 
+ *   that are non-power-of-two and/or rectangular.
+ */
+BulletHeightfieldShape::
+BulletHeightfieldShape(Texture *tex, PN_stdfloat max_height, BulletUpAxis up) {
+
+  _num_rows = tex->get_x_size() + 1;
+  _num_cols = tex->get_y_size() + 1;
+  _data = new float[_num_rows * _num_cols];
+
+  PN_stdfloat step_x = 1.0 / (PN_stdfloat)tex->get_x_size();
+  PN_stdfloat step_y = 1.0 / (PN_stdfloat)tex->get_y_size();
+
+  PT(TexturePeeker) peeker = tex->peek();
+  LColor sample;
+
+  for (int row=0; row < _num_rows; row++) {
+    for (int column=0; column < _num_cols; column++) {
+      if (!peeker->lookup_bilinear(sample, row * step_x, column * step_y)) {
+        bullet_cat.error() << "Could not sample texture." << endl;
+      }
+      // Transpose
+      _data[_num_rows * column + row] = max_height * sample.get_x();
+    }
+  }
+
+  _shape = new btHeightfieldTerrainShape(_num_rows,
+                                         _num_cols,
+                                         _data,
+                                         max_height,
+                                         up,
+                                         true, false);
+  _shape->setUserPointer(this);
+}

panda/src/bullet/bulletHeightfieldShape.h

@@ -21,6 +21,8 @@
 #include "bulletShape.h"
 
 #include "pnmImage.h"
+#include "texture.h"
+#include "texturePeeker.h"
 
 /**
  *
@@ -29,6 +31,7 @@ class EXPCL_PANDABULLET BulletHeightfieldShape : public BulletShape {
 
 PUBLISHED:
   BulletHeightfieldShape(const PNMImage &image, PN_stdfloat max_height, BulletUpAxis up=Z_up);
+  BulletHeightfieldShape(Texture *tex, PN_stdfloat max_height, BulletUpAxis up=Z_up);
   INLINE BulletHeightfieldShape(const BulletHeightfieldShape &copy);
   INLINE void operator = (const BulletHeightfieldShape &copy);
   INLINE ~BulletHeightfieldShape();

panda/src/bullet/bulletManifoldPoint.cxx

@@ -92,7 +92,7 @@ get_position_world_on_b() const {
 LPoint3 BulletManifoldPoint::
 get_normal_world_on_b() const {
 
-  return btVector3_to_LPoint3(_pt.m_normalWorldOnB);
+  return btVector3_to_LVector3(_pt.m_normalWorldOnB);
 }
 
 /**

panda/src/bullet/bulletManifoldPoint.h

@@ -34,7 +34,7 @@ PUBLISHED:
   PN_stdfloat get_applied_impulse() const;
   LPoint3 get_position_world_on_a() const;
   LPoint3 get_position_world_on_b() const;
-  LPoint3 get_normal_world_on_b() const;
+  LVector3 get_normal_world_on_b() const;
   LPoint3 get_local_point_a() const;
   LPoint3 get_local_point_b() const;