From b4da9241f64f1aeba27c87b2eddfec4d559de8ac Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Sun, 2 Oct 2011 21:06:56 +0900
Subject: [PATCH] Make a fresh start on box clipping.

I even have a failing test to fix :)
---
 libs/models/test/testclip.c | 33 +++++++++++++++++++++++++++++++++
 libs/models/trace.c         | 21 ++++++++++++++++++---
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/libs/models/test/testclip.c b/libs/models/test/testclip.c
index a29c57888..d4dfd4734 100644
--- a/libs/models/test/testclip.c
+++ b/libs/models/test/testclip.c
@@ -118,6 +118,33 @@ hull_t hull_tppw = {
 	{0, 0, 0},
 };
 
+//     2
+//  eee|eee
+// 0,32+--- 1
+//  eee|sss
+//  ---+--- 0
+//  ss0,0ss
+mclipnode_t clipnodes_step1[] = {
+	{  0, {             1, CONTENTS_SOLID}},
+	{  1, {CONTENTS_EMPTY,              2}},
+	{  2, {CONTENTS_SOLID, CONTENTS_EMPTY}},
+};
+
+mplane_t planes_step1[] = {
+	{{0, 0, 1},   0, 2, 0},
+	{{0, 0, 1},  32, 2, 0},
+	{{1, 0, 0},   0, 0, 0},
+};
+
+hull_t hull_step1 = {
+	clipnodes_step1,
+	planes_step1,
+	0,
+	2,
+	{0, 0, 0},
+	{0, 0, 0},
+};
+
 typedef struct {
 	vec3_t      extents;
 } box_t;
@@ -138,6 +165,7 @@ typedef struct {
 } test_t;
 
 box_t point = { {0, 0, 0} };
+box_t box =   { {8, 8, 8} };
 box_t player = { {16, 16, 28} };
 
 test_t tests[] = {
@@ -177,6 +205,11 @@ test_t tests[] = {
 		{ 40, 0, 0}, { 40, 8, 0}, {     1, 0, 0, 0, 1}},
 	{"Point, Three parallel planes with water", &point, &hull_tppw,
 		{  0, 0, 0}, { 40, 0, 0}, {     1, 0, 0, 1, 1}},
+
+	{"Point, Step 1", &point, &hull_step1,
+		{ -16, 0, 8}, {16, 0, 24}, { 0.5, 0, 0, 1, 0}},
+	{"Box, Step 1", &box, &hull_step1,
+		{ -16, 0, 8}, {16, 0, 24}, { 0.25, 0, 0, 1, 0}},
 };
 #define num_tests (sizeof (tests) / sizeof (tests[0]))
 
diff --git a/libs/models/trace.c b/libs/models/trace.c
index 1cb02d00a..ded4eab41 100644
--- a/libs/models/trace.c
+++ b/libs/models/trace.c
@@ -61,6 +61,20 @@ typedef struct {
 	mplane_t   *plane;
 } tracestack_t;
 
+static inline float
+calc_offset (trace_t *trace, mplane_t *plane)
+{
+	if (trace->isbox) {
+		if (plane->type < 3)
+			return trace->extents[plane->type];
+		else
+			return (fabs (trace->extents[0] * plane->normal[0])
+					+ fabs (trace->extents[1] * plane->normal[1])
+					+ fabs (trace->extents[2] * plane->normal[2]));
+	}
+	return 0;
+}
+
 static inline void
 calc_impact (trace_t *trace, const vec3_t start, const vec3_t end,
 			 mplane_t *plane)
@@ -92,7 +106,7 @@ MOD_TraceLine (hull_t *hull, int num,
 			   const vec3_t start_point, const vec3_t end_point,
 			   trace_t *trace)
 {
-	vec_t       start_dist, end_dist, frac;
+	vec_t       start_dist, end_dist, frac, offset;
 	vec3_t      start, end, dist;
 	int         side;
 	qboolean    seen_empty, seen_solid;
@@ -164,13 +178,14 @@ MOD_TraceLine (hull_t *hull, int num,
 
 		start_dist = PlaneDiff (start, plane);
 		end_dist = PlaneDiff (end, plane);
+		offset = calc_offset (trace, plane);
 
-		if (start_dist >= 0 && end_dist >= 0) {
+		if (start_dist >= offset && end_dist >= offset) {
 			// entirely in front of the plane
 			num = node->children[0];
 			continue;
 		}
-		if (start_dist < 0 && end_dist < 0) {
+		if (start_dist < offset && end_dist < offset) {
 			// entirely behind the plane
 			num = node->children[1];
 			continue;