From cd39c3b8d1ac4e4866460aeee1bc85c2ad070958 Mon Sep 17 00:00:00 2001
From: fincs <fincs.alt1@gmail.com>
Date: Thu, 26 Nov 2015 12:28:09 +0100
Subject: [PATCH] Improve and correct support for light distance attenuation

---
 include/c3d/light.h    |  3 +--
 include/c3d/lightlut.h | 14 ++++++++++++++
 source/light.c         | 21 ++++++++-------------
 source/lightlut.c      | 20 ++++++++++++++++++++
 4 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/include/c3d/light.h b/include/c3d/light.h
index f91f910..f07141c 100644
--- a/include/c3d/light.h
+++ b/include/c3d/light.h
@@ -118,5 +118,4 @@ void C3D_LightSpotEnable(C3D_Light* light, bool enable);
 void C3D_LightSpotDir(C3D_Light* light, float x, float y, float z);
 void C3D_LightSpotLut(C3D_Light* light, C3D_LightLut* lut);
 void C3D_LightDistAttnEnable(C3D_Light* light, bool enable);
-void C3D_LightDistAttn(C3D_Light* light, float bias, float scale);
-void C3D_LightDistAttnLut(C3D_Light* light, C3D_LightLut* lut);
+void C3D_LightDistAttn(C3D_Light* light, C3D_LightLutDA* lut);
diff --git a/include/c3d/lightlut.h b/include/c3d/lightlut.h
index b718b97..b9e0a5b 100644
--- a/include/c3d/lightlut.h
+++ b/include/c3d/lightlut.h
@@ -7,9 +7,23 @@ typedef struct
 	u32 data[256];
 } C3D_LightLut;
 
+typedef struct
+{
+	C3D_LightLut lut;
+	float bias, scale;
+} C3D_LightLutDA;
+
 typedef float (* C3D_LightLutFunc)(float x, float param);
+typedef float (* C3D_LightLutFuncDA)(float dist, float arg0, float arg1);
+
+static inline float quadratic_dist_attn(float dist, float linear, float quad)
+{
+	return 1.0f / (1.0f + linear*dist + quad*dist*dist);
+}
 
 void LightLut_FromArray(C3D_LightLut* lut, float* data);
 void LightLut_FromFunc(C3D_LightLut* lut, C3D_LightLutFunc func, float param, bool negative);
+void LightLutDA_Create(C3D_LightLutDA* lut, C3D_LightLutFuncDA func, float from, float to, float arg0, float arg1);
 
 #define LightLut_Phong(lut, shininess) LightLut_FromFunc((lut), powf, (shininess), false)
+#define LightLutDA_Quadratic(lut, from, to, linear, quad) LightLutDA_Create((lut), quadratic_dist_attn, (from), (to), (linear), (quad))
diff --git a/source/light.c b/source/light.c
index 99252c5..f9e4b96 100644
--- a/source/light.c
+++ b/source/light.c
@@ -92,7 +92,7 @@ static void C3Di_EnableCommon(C3D_Light* light, bool enable, u32 bit)
 	C3D_LightEnv* env = light->parent;
 	u32* var = &env->conf.config[1];
 
-	if ((*var & bit) ^ bit)
+	if (enable == !(*var & bit))
 		return;
 
 	if (!enable)
@@ -134,19 +134,14 @@ void C3D_LightDistAttnEnable(C3D_Light* light, bool enable)
 	C3Di_EnableCommon(light, enable, GPU_LC1_ATTNBIT(light->id));
 }
 
-void C3D_LightDistAttn(C3D_Light* light, float bias, float scale)
-{
-	C3Di_EnableCommon(light, true, GPU_LC1_ATTNBIT(light->id));
-	light->conf.distAttnBias  = f32tof20(bias);
-	light->conf.distAttnScale = f32tof20(scale);
-	light->flags |= C3DF_Light_Dirty;
-}
-
-void C3D_LightDistAttnLut(C3D_Light* light, C3D_LightLut* lut)
+void C3D_LightDistAttn(C3D_Light* light, C3D_LightLutDA* lut)
 {
 	bool hasLut = lut != NULL;
 	C3Di_EnableCommon(light, hasLut, GPU_LC1_ATTNBIT(light->id));
-	light->lut_DA = lut;
-	if (hasLut)
-		light->flags |= C3DF_Light_DADirty;
+	if (!hasLut) return;
+
+	light->conf.distAttnBias  = f32tof20(lut->bias);
+	light->conf.distAttnScale = f32tof20(lut->scale);
+	light->lut_DA = &lut->lut;
+	light->flags |= C3DF_Light_Dirty | C3DF_Light_DADirty;
 }
diff --git a/source/lightlut.c b/source/lightlut.c
index 400af86..b49534a 100644
--- a/source/lightlut.c
+++ b/source/lightlut.c
@@ -44,3 +44,23 @@ void LightLut_FromFunc(C3D_LightLut* lut, C3D_LightLutFunc func, float param, bo
 	}
 	LightLut_FromArray(lut, data);
 }
+
+void LightLutDA_Create(C3D_LightLutDA* lut, C3D_LightLutFuncDA func, float from, float to, float arg0, float arg1)
+{
+	int i;
+	float data[512];
+	data[511] = 0;
+
+	lut->scale = 1.0f / (to-from);
+	lut->bias = -from*lut->scale;
+
+	for (i = 0; i < 256; i ++)
+	{
+		float dist = ((float)i/255 - lut->bias) / lut->scale;
+		data[i] = func(dist, arg0, arg1);
+		if (i > 0)
+			data[i+255] = data[i]-data[i-1];
+	}
+
+	LightLut_FromArray(&lut->lut, data);
+}