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

1 files changed, 3 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/lamp.c b/source/blender/blenkernel/intern/lamp.c
index 9601a93b1f1..49a573489ef 100644
--- a/source/blender/blenkernel/intern/lamp.c
+++ b/source/blender/blenkernel/intern/lamp.c
@@ -79,6 +79,9 @@ void BKE_lamp_init(Lamp *la)
 	la->adapt_thresh = 0.001f;
 	la->preview = NULL;
 	la->falloff_type = LA_FALLOFF_INVSQUARE;
+	la->coeff_const = 1.0f;
+	la->coeff_lin = 0.0f;
+	la->coeff_quad = 0.0f;
 	la->curfalloff = curvemapping_add(1, 0.0f, 1.0f, 1.0f, 0.0f);
 	la->sun_effect_type = 0;
 	la->horizon_brightness = 1.0;