Cycles / Sky Model:

* Replaced the Preetham model with the newer Hosek / Wilkie model:
"An Analytic Model for Full Spectral Sky-Dome Radiance" http://cgg.mff.cuni.cz/projects/SkylightModelling/ 

* We use the sample code data, which comes with the paper, but removed some unnecessary parts, we only need the xyz version.
* New "Albedo" UI paraemeter, to control the ground albedo (between 0 and 1). 
* Works with SVM only atm (CPU and CUDA). 

Example render:
http://www.pasteall.org/pic/show.php?id=57635

ToDo / Open Questions:
* OSL still uses the old model, will be done later. In the meantime it's useful to compare the two models this way.
* The new model needs a much weaker Strength value (0.01), otherwise it's white. Can this be fixed? 
* Code cleanup. 

4 files changed, 8 insertions, 0 deletions

diff --git a/source/blender/editors/space_node/drawnode.c b/source/blender/editors/space_node/drawnode.c
index 5cc22b25f72..7c35ec1fb00 100644
--- a/source/blender/editors/space_node/drawnode.c
+++ b/source/blender/editors/space_node/drawnode.c
@@ -812,6 +812,7 @@ static void node_shader_buts_tex_sky(uiLayout *layout, bContext *UNUSED(C), Poin
 {
 	uiItemR(layout, ptr, "sun_direction", 0, "", ICON_NONE);
 	uiItemR(layout, ptr, "turbidity", 0, NULL, ICON_NONE);
+	uiItemR(layout, ptr, "albedo", 0, NULL, ICON_NONE);
 }
 
 static void node_shader_buts_tex_gradient(uiLayout *layout, bContext *UNUSED(C), PointerRNA *ptr)
diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index 109cdf5f1a1..05ae1b241ab 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -722,6 +722,7 @@ typedef struct NodeTexSky {
 	NodeTexBase base;
 	float sun_direction[3];
 	float turbidity;
+	float albedo;
 } NodeTexSky;
 
 typedef struct NodeTexImage {
diff --git a/source/blender/makesrna/intern/rna_nodetree.c b/source/blender/makesrna/intern/rna_nodetree.c
index 3b594ab0961..a23a7fa998f 100644
--- a/source/blender/makesrna/intern/rna_nodetree.c
+++ b/source/blender/makesrna/intern/rna_nodetree.c
@@ -3243,6 +3243,11 @@ static void def_sh_tex_sky(StructRNA *srna)
 	RNA_def_property_range(prop, 1.0f, 30.0f);
 	RNA_def_property_ui_text(prop, "Turbidity", "Atmospheric turbidity");
 	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+	
+	prop = RNA_def_property(srna, "albedo", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_range(prop, 0.0f, 1.0f);
+	RNA_def_property_ui_text(prop, "Albedo", "Ground albedo");
+	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
 }
 
 static void def_sh_tex_environment(StructRNA *srna)
diff --git a/source/blender/nodes/shader/nodes/node_shader_tex_sky.c b/source/blender/nodes/shader/nodes/node_shader_tex_sky.c
index f9cd4b72912..c31255e201a 100644
--- a/source/blender/nodes/shader/nodes/node_shader_tex_sky.c
+++ b/source/blender/nodes/shader/nodes/node_shader_tex_sky.c
@@ -48,6 +48,7 @@ static void node_shader_init_tex_sky(bNodeTree *UNUSED(ntree), bNode *node)
 	tex->sun_direction[1] = 0.0f;
 	tex->sun_direction[2] = 1.0f;
 	tex->turbidity = 2.2f;
+	tex->albedo = 0.3f;
 
 	node->storage = tex;
 }