From d0fb0bd4100fe6fd76272906918c66d925e78aa5 Mon Sep 17 00:00:00 2001
From: Eric Wasylishen <ewasylishen@gmail.com>
Date: Sun, 25 Oct 2015 23:18:17 -0600
Subject: [PATCH] light: remove entity->fadedist, it was error-prone, and
 instead just check light level. it's only very slightly slower.

---
 include/light/entities.h |  1 -
 light/entities.c         | 31 -------------------------------
 light/ltface.c           | 17 +++++++++--------
 3 files changed, 9 insertions(+), 40 deletions(-)

diff --git a/include/light/entities.h b/include/light/entities.h
index 59837c98..4f6d8828 100644
--- a/include/light/entities.h
+++ b/include/light/entities.h
@@ -63,7 +63,6 @@ typedef struct entity_s {
 
     lightsample_t light;
     light_formula_t formula;
-    vec_t fadedist;
     float atten;
     float anglescale;
     int style;
diff --git a/light/entities.c b/light/entities.c
index 54231dce..ec026ac4 100644
--- a/light/entities.c
+++ b/light/entities.c
@@ -254,37 +254,6 @@ CheckEntityFields(entity_t *entity)
     } else {
 	VectorCopy(vec3_white, entity->light.color);
     }
-
-    if (entity->formula == LF_LINEAR) {
-	/* Linear formula always has a falloff point */
-	entity->fadedist = fabs(entity->light.light) - fadegate;
-	entity->fadedist = entity->fadedist / entity->atten / scaledist;
-	entity->fadedist = qmax(0.0f, entity->fadedist);
-    } else if (fadegate < EQUAL_EPSILON) {
-	/* If fadegate is tiny, other lights have effectively infinite reach */
-	entity->fadedist = VECT_MAX;
-    } else {
-	/* Calculate the distance at which brightness falls to zero */
-	switch (entity->formula) {
-	case LF_INFINITE:
-	case LF_LOCALMIN:
-	    entity->fadedist = VECT_MAX;
-	    break;
-	case LF_INVERSE:
-	    entity->fadedist = (LF_SCALE * fabs(entity->light.light)) / (scaledist * entity->atten * fadegate);
-	    break;
-	case LF_INVERSE2:
-	case LF_INVERSE2A:
-	    entity->fadedist = sqrt(fabs(entity->light.light * SQR(LF_SCALE) / (SQR(scaledist) * SQR(entity->atten) * fadegate)));
-	    if (entity->formula == LF_INVERSE2A) {
-		entity->fadedist -= (LF_SCALE / (scaledist * entity->atten));
-	    }
-	    entity->fadedist = qmax(0.0f, entity->fadedist);
-	    break;
-	default:
-	    Error("Internal error: formula not handled in %s", __func__);
-	}
-    }
 }
 
 /*
diff --git a/light/ltface.c b/light/ltface.c
index dc3c6317..1b99b617 100644
--- a/light/ltface.c
+++ b/light/ltface.c
@@ -813,10 +813,15 @@ CullLight(const entity_t *entity, const lightsurf_t *lightsurf)
     vec_t dist;
     
     VectorSubtract(entity->origin, lightsurf->origin, distvec);
-    dist = VectorLength(distvec) - lightsurf->radius - entity->fadedist;
+    dist = VectorLength(distvec) - lightsurf->radius;
     
-    /* return true if the spheres don't intersect */
-    return dist > 0;
+    /* light is inside surface bounding sphere => can't cull */
+    if (dist < 0)
+	return false;
+    
+    /* return true if the light level at the closest point on the
+       surface bounding sphere to the light source is <= fadegate */
+    return GetLightValue(&entity->light, entity, dist) <= fadegate;
 }
 
 /*
@@ -844,10 +849,6 @@ LightFace_Entity(const entity_t *entity, const lightsample_t *light,
     if (dist < 0)
 	return;
 
-    /* don't bother with light too far away from plane */
-    if (dist > entity->fadedist)
-	return;
-
     /* sphere cull surface and light */
     if (CullLight(entity, lightsurf))
 	return;
@@ -867,7 +868,7 @@ LightFace_Entity(const entity_t *entity, const lightsample_t *light,
 	dist = VectorLength(ray);
 
 	/* Quick distance check first */
-	if (dist > entity->fadedist)
+	if (GetLightValue(&entity->light, entity, dist) <= fadegate)
 	    continue;
 
 	/* Check spotlight cone */