Full Inverse-Quadratic-Equation Lamp Falloff

This patch adds a new `falloff_type` ('Inverse Coefficients') for Lamps in
Blender-Internal and GLSL.

The current falloff modes use a formula like this inverse-square one:

`I = E × (D^2 / (D^2 + Q × r^2))`

While such a formula is simple for 3D-artists to use, it's algebraically
cumbersome to work with. Game-designers authoring their own shaders
could benefit much more by having direct control of falloff-coefficients:

`I = E × (1.0 / (coefC + coefL × r + coefQ × r^2))`

In this mode, the `distance` parameter is unused (except for 'Sphere'
mode); instead relying on the designer to mathematically-model the
falloff-behavior.

The UI has been patched like so:
{F153843}

Reviewers: brecht, psy-fi

Reviewed By: psy-fi

Subscribers: brita_, antidote, campbellbarton, psy-fi

Differential Revision: https://developer.blender.org/D1194

3 files changed, 6 insertions, 2 deletions

diff --git a/source/gameengine/Converter/BL_BlenderDataConversion.cpp b/source/gameengine/Converter/BL_BlenderDataConversion.cpp
index 20281eb986e..c2cfd8808a9 100644
--- a/source/gameengine/Converter/BL_BlenderDataConversion.cpp
+++ b/source/gameengine/Converter/BL_BlenderDataConversion.cpp
@@ -1417,6 +1417,9 @@ static KX_LightObject *gamelight_from_blamp(Object *ob, Lamp *la, unsigned int l
 	
 	lightobj->m_att1 = la->att1;
 	lightobj->m_att2 = (la->mode & LA_QUAD) ? la->att2 : 0.0f;
+	lightobj->m_coeff_const = la->coeff_const;
+	lightobj->m_coeff_lin = la->coeff_lin;
+	lightobj->m_coeff_quad = la->coeff_quad;
 	lightobj->m_color[0] = la->r;
 	lightobj->m_color[1] = la->g;
 	lightobj->m_color[2] = la->b;
diff --git a/source/gameengine/Rasterizer/RAS_ILightObject.h b/source/gameengine/Rasterizer/RAS_ILightObject.h
index 59475200a73..a3d55c925d6 100644
--- a/source/gameengine/Rasterizer/RAS_ILightObject.h
+++ b/source/gameengine/Rasterizer/RAS_ILightObject.h
@@ -69,6 +69,7 @@ public:
 
 	float	m_att1;
 	float	m_att2;
+	float	m_coeff_const, m_coeff_lin, m_coeff_quad;
 	float	m_spotsize;
 	float	m_spotblend;
 
diff --git a/source/gameengine/Rasterizer/RAS_OpenGLRasterizer/RAS_OpenGLLight.cpp b/source/gameengine/Rasterizer/RAS_OpenGLRasterizer/RAS_OpenGLLight.cpp
index 7639189a6f0..e15ae4bd0d7 100644
--- a/source/gameengine/Rasterizer/RAS_OpenGLRasterizer/RAS_OpenGLLight.cpp
+++ b/source/gameengine/Rasterizer/RAS_OpenGLRasterizer/RAS_OpenGLLight.cpp
@@ -59,7 +59,7 @@ RAS_OpenGLLight::~RAS_OpenGLLight()
 	if ((lamp = GetGPULamp())) {
 		float obmat[4][4] = {{0}};
 		GPU_lamp_update(lamp, 0, 0, obmat);
-		GPU_lamp_update_distance(lamp, la->dist, la->att1, la->att2);
+		GPU_lamp_update_distance(lamp, la->dist, la->att1, la->att2, la->coeff_const, la->coeff_lin, la->coeff_quad);
 		GPU_lamp_update_spot(lamp, la->spotsize, la->spotblend);
 	}
 }
@@ -291,7 +291,7 @@ void RAS_OpenGLLight::Update()
 		GPU_lamp_update(lamp, m_layer, hide, obmat);
 		GPU_lamp_update_colors(lamp, m_color[0], m_color[1],
 			m_color[2], m_energy);
-		GPU_lamp_update_distance(lamp, m_distance, m_att1, m_att2);
+		GPU_lamp_update_distance(lamp, m_distance, m_att1, m_att2, m_coeff_const, m_coeff_lin, m_coeff_quad);
 		GPU_lamp_update_spot(lamp, m_spotsize, m_spotblend);
 	}
 }