From: Daniel Karbach <daniel.karbach@localhorst.tv>
Date: Tue, 23 Jun 2015 12:54:00 +0000 (+0200)
Subject: box/box intersection test
X-Git-Url: https://git.localhorst.tv/?a=commitdiff_plain;h=0580ff3941fe5f5ea25c96e737edba1541d9271f;p=blank.git

box/box intersection test

only boolean test for now
---

diff --git a/src/model/geometry.cpp b/src/model/geometry.cpp
index ed9b4b7..b08d59f 100644
--- a/src/model/geometry.cpp
+++ b/src/model/geometry.cpp
@@ -65,6 +65,71 @@ bool Intersection(
 	return true;
 }
 
+
+bool Intersection(
+	const AABB &a_box,
+	const glm::mat4 &a_m,
+	const AABB &b_box,
+	const glm::mat4 &b_m
+) noexcept {
+	glm::vec3 a_corners[8] = {
+		glm::vec3(a_m * glm::vec4(a_box.min.x, a_box.min.y, a_box.min.z, 1)),
+		glm::vec3(a_m * glm::vec4(a_box.min.x, a_box.min.y, a_box.max.z, 1)),
+		glm::vec3(a_m * glm::vec4(a_box.min.x, a_box.max.y, a_box.min.z, 1)),
+		glm::vec3(a_m * glm::vec4(a_box.min.x, a_box.max.y, a_box.max.z, 1)),
+		glm::vec3(a_m * glm::vec4(a_box.max.x, a_box.min.y, a_box.min.z, 1)),
+		glm::vec3(a_m * glm::vec4(a_box.max.x, a_box.min.y, a_box.max.z, 1)),
+		glm::vec3(a_m * glm::vec4(a_box.max.x, a_box.max.y, a_box.min.z, 1)),
+		glm::vec3(a_m * glm::vec4(a_box.max.x, a_box.max.y, a_box.max.z, 1)),
+	};
+
+	glm::vec3 b_corners[8] = {
+		glm::vec3(b_m * glm::vec4(b_box.min.x, b_box.min.y, b_box.min.z, 1)),
+		glm::vec3(b_m * glm::vec4(b_box.min.x, b_box.min.y, b_box.max.z, 1)),
+		glm::vec3(b_m * glm::vec4(b_box.min.x, b_box.max.y, b_box.min.z, 1)),
+		glm::vec3(b_m * glm::vec4(b_box.min.x, b_box.max.y, b_box.max.z, 1)),
+		glm::vec3(b_m * glm::vec4(b_box.max.x, b_box.min.y, b_box.min.z, 1)),
+		glm::vec3(b_m * glm::vec4(b_box.max.x, b_box.min.y, b_box.max.z, 1)),
+		glm::vec3(b_m * glm::vec4(b_box.max.x, b_box.max.y, b_box.min.z, 1)),
+		glm::vec3(b_m * glm::vec4(b_box.max.x, b_box.max.y, b_box.max.z, 1)),
+	};
+
+	glm::vec3 axes[6] = {
+		glm::vec3(a_m * glm::vec4(1, 0, 0, 0)),
+		glm::vec3(a_m * glm::vec4(0, 1, 0, 0)),
+		glm::vec3(a_m * glm::vec4(0, 0, 1, 0)),
+		glm::vec3(b_m * glm::vec4(1, 0, 0, 0)),
+		glm::vec3(b_m * glm::vec4(0, 1, 0, 0)),
+		glm::vec3(b_m * glm::vec4(0, 0, 1, 0)),
+	};
+
+	for (const glm::vec3 &axis : axes) {
+		float a_min = std::numeric_limits<float>::infinity();
+		float a_max = -std::numeric_limits<float>::infinity();
+		for (const glm::vec3 &corner : a_corners) {
+			float val = glm::dot(corner, axis);
+			a_min = std::min(a_min, val);
+			a_max = std::max(a_max, val);
+		}
+
+		float b_min = std::numeric_limits<float>::infinity();
+		float b_max = -std::numeric_limits<float>::infinity();
+		for (const glm::vec3 &corner : b_corners) {
+			float val = glm::dot(corner, axis);
+			b_min = std::min(b_min, val);
+			b_max = std::max(b_max, val);
+		}
+
+		if (a_max < b_min || b_max < a_min) return false;
+	}
+
+	// TODO: find intersection point and normals
+	// normal could be deduced from the axis with the lowest min?
+
+	return true;
+}
+
+
 bool CullTest(const AABB &box, const glm::mat4 &MVP) noexcept {
 	// transform corners into clip space
 	glm::vec4 corners[8] = {
diff --git a/src/model/geometry.hpp b/src/model/geometry.hpp
index d6e3d28..f4498f5 100644
--- a/src/model/geometry.hpp
+++ b/src/model/geometry.hpp
@@ -36,6 +36,12 @@ bool Intersection(
 	float *dist = nullptr,
 	glm::vec3 *normal = nullptr) noexcept;
 
+bool Intersection(
+	const AABB &a_box,
+	const glm::mat4 &a_m,
+	const AABB &b_box,
+	const glm::mat4 &b_m) noexcept;
+
 bool CullTest(const AABB &box, const glm::mat4 &MVP) noexcept;
 
 }
diff --git a/tst/model/GeometryTest.cpp b/tst/model/GeometryTest.cpp
index 51985ae..71830c6 100644
--- a/tst/model/GeometryTest.cpp
+++ b/tst/model/GeometryTest.cpp
@@ -4,6 +4,7 @@
 
 #include <limits>
 #include <glm/gtx/io.hpp>
+#include <glm/gtx/transform.hpp>
 
 CPPUNIT_TEST_SUITE_REGISTRATION(blank::test::GeometryTest);
 
@@ -18,7 +19,7 @@ void GeometryTest::tearDown() {
 }
 
 
-void GeometryTest::testRayAABBIntersection() {
+void GeometryTest::testRayBoxIntersection() {
 	Ray ray{ { 0, 0, 0 }, { 1, 0, 0 } }; // at origin, pointing right
 	AABB box{ { -1, -1, -1 }, { 1, 1, 1 } }; // 2x2x2 cube centered around origin
 	glm::mat4 M(1); // no transformation
@@ -62,5 +63,38 @@ void GeometryTest::testRayAABBIntersection() {
 	);
 }
 
+void GeometryTest::testBoxBoxIntersection() {
+	AABB box{ { -1, -1, -1 }, { 1, 1, 1 } }; // 2x2x2 cube centered around origin
+	glm::mat4 Ma(1); // identity
+	glm::mat4 Mb(1); // identity
+	// they're identical, so should probably intersect ^^
+
+	CPPUNIT_ASSERT_MESSAGE(
+		"identical OBBs don't intersect",
+		Intersection(box, Ma, box, Mb)
+	);
+
+	Ma = glm::translate(glm::vec3(-2, 0, 0)); // 2 to the left
+	Mb = glm::translate(glm::vec3(2, 0, 0)); // 2 to the right
+	CPPUNIT_ASSERT_MESSAGE(
+		"distant OBBs intersect (2 apart, no rotation)",
+		!Intersection(box, Ma, box, Mb)
+	);
+
+	Ma = glm::rotate(PI_0p25, glm::vec3(0, 0, 1)); // rotated 45° around Z
+	Mb = glm::translate(glm::vec3(2.4, 0, 0)); // 2.4 to the right
+	// they should barely touch. intersect by about 0.01 if my head works
+	CPPUNIT_ASSERT_MESSAGE(
+		"OBBs don't intersect (one rotated by 45°)",
+		Intersection(box, Ma, box, Mb)
+	);
+
+	Mb = glm::translate(glm::vec3(3, 0, 0)); // 3 to the right
+	CPPUNIT_ASSERT_MESSAGE(
+		"OBBs intersect (one rotated by 45°)",
+		!Intersection(box, Ma, box, Mb)
+	);
+}
+
 }
 }
diff --git a/tst/model/GeometryTest.hpp b/tst/model/GeometryTest.hpp
index 2ee85b1..7ba2d2d 100644
--- a/tst/model/GeometryTest.hpp
+++ b/tst/model/GeometryTest.hpp
@@ -12,7 +12,8 @@ class GeometryTest
 
 CPPUNIT_TEST_SUITE(GeometryTest);
 
-CPPUNIT_TEST(testRayAABBIntersection);
+CPPUNIT_TEST(testRayBoxIntersection);
+CPPUNIT_TEST(testBoxBoxIntersection);
 
 CPPUNIT_TEST_SUITE_END();
 
@@ -20,7 +21,8 @@ public:
 	void setUp();
 	void tearDown();
 
-	void testRayAABBIntersection();
+	void testRayBoxIntersection();
+	void testBoxBoxIntersection();
 
 };