Commit 527b5853 authored by Makayla Shepherd's avatar Makayla Shepherd
Browse files

Corrected the shaded value algorithm. Fixes #4326 

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/branches/ipce@7263 41f8697f-d340-4b68-9986-7bafba869bb8
parent 46e21d86

isis/src/base/objs/Hillshade/Hillshade.cpp

+2 −2
Original line number Diff line number Diff line
@@ -256,7 +256,7 @@ namespace Isis { 


                            1 + p0*p + q0*q

      shade =  -------------------------------------------------

                 sqrt(1 + p*p + Q*q) + sqrt(1 + p0*p0 + q0*q0)

                 sqrt(1 + p*p + q*q) * sqrt(1 + p0*p0 + q0*q0)



      where p0 = -cos( sun azimuth ) * tan( solar elevation ) and

            q0 = -sin( sun azimuth ) * tan( solar elevation )
@@ -273,7 +273,7 @@ namespace Isis { 


      double numerator = 1.0 + p0 * p + q0 * q;



      double denominator = sqrt(1 + p * p + q * q) + sqrt(1 + p0 * p0 + q0 * q0);

      double denominator = sqrt(1 + p * p + q * q) * sqrt(1 + p0 * p0 + q0 * q0);



      result = numerator / denominator;

    }

isis/src/base/objs/Hillshade/Hillshade.h

+2 −0
Original line number Diff line number Diff line
@@ -25,6 +25,8 @@ namespace Isis { 
   * @author 2012-10-25 Steven Lambright

   *

   * @internal

   *   @history 2016-11-21 Makayla Shepherd - Corrected the shaded value algorithm in shadedValue. 

   *                           Fixes #4326.

   */

  class Hillshade {

    public:

isis/src/base/objs/Hillshade/Hillshade.truth

+9 −9
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@@ -8,15 +8,15 @@ Assigned valid: Hillshade[ azimuth = 0.0 degrees zenith = 15.0 degrees resolutio 




Test computations

Shaded value (flat surface, sun directly up): 0.5

Shaded value (rotated sun's direction):       0.5

Shaded value (lowered solar elevation):       0.49617287

Shaded value (sun is next to the horizon):    0.017153045

Shaded value (solar elevation is 45):         0.41421356

Shaded value (surface tilted towards sun):    0.63708941

Shaded value (surface folded inwards):        0.63708941

Shaded value (surface folded outwards):       0.63708941

Shaded value (surface facing away):          -0.43701602

Shaded value (flat surface, sun directly up): 1

Shaded value (rotated sun's direction):       1

Shaded value (lowered solar elevation):       0.98480775

Shaded value (sun is next to the horizon):    0.017452406

Shaded value (solar elevation is 45):         0.70710678

Shaded value (surface tilted towards sun):    0.98058068

Shaded value (surface folded inwards):        0.98058068

Shaded value (surface folded outwards):       0.98058068

Shaded value (surface facing away):          -0.4472136

Shaded value special (special pixel in surface): 1



Test error handling