Add initial prototype.

3-mid/physics/implement/box2d/contrib/testbed/tests/skier.cpp

@@ -0,0 +1,150 @@
+/*
+Test case for collision/jerking issue.
+*/
+
+#include "test.h"
+
+#include <vector>
+#include <iostream>
+
+class Skier : public Test
+{
+public:
+	Skier()
+	{		
+		b2Body* ground = NULL;
+		{
+			b2BodyDef bd;
+			ground = m_world->CreateBody(&bd);
+
+			float const PlatformWidth = 8.0f;
+
+			/*
+			First angle is from the horizontal and should be negative for a downward slope.
+			Second angle is relative to the preceding slope, and should be positive, creating a kind of
+			loose 'Z'-shape from the 3 edges.
+			If A1 = -10, then A2 <= ~1.5 will result in the collision glitch.
+			If A1 = -30, then A2 <= ~10.0 will result in the glitch.
+			*/
+			float const Angle1Degrees = -30.0f;
+			float const Angle2Degrees = 10.0f;
+			
+			/*
+			The larger the value of SlopeLength, the less likely the glitch will show up.
+			*/
+			float const SlopeLength = 2.0f;
+
+			float const SurfaceFriction = 0.2f;
+
+			// Convert to radians
+			float const Slope1Incline = -Angle1Degrees * b2_pi / 180.0f;
+			float const Slope2Incline = Slope1Incline - Angle2Degrees * b2_pi / 180.0f;
+			//
+
+			m_platform_width = PlatformWidth;
+
+			// Horizontal platform
+			b2Vec2 v1(-PlatformWidth, 0.0f);
+			b2Vec2 v2(0.0f, 0.0f);
+			b2Vec2 v3(SlopeLength * cosf(Slope1Incline), -SlopeLength * sinf(Slope1Incline));
+			b2Vec2 v4(v3.x + SlopeLength * cosf(Slope2Incline), v3.y - SlopeLength * sinf(Slope2Incline));
+			b2Vec2 v5(v4.x, v4.y - 1.0f);
+
+			b2Vec2 vertices[5] = { v5, v4, v3, v2, v1 };
+
+			b2ChainShape shape;
+			shape.CreateLoop(vertices, 5);
+			b2FixtureDef fd;
+			fd.shape = &shape;
+			fd.density = 0.0f;
+			fd.friction = SurfaceFriction;
+
+			ground->CreateFixture(&fd);
+		}
+
+		{
+			float const BodyWidth = 1.0f;
+			float const BodyHeight = 2.5f;
+			float const SkiLength = 3.0f;
+
+			/*
+			Larger values for this seem to alleviate the issue to some extent.
+			*/
+			float const SkiThickness = 0.3f;
+
+			float const SkiFriction = 0.0f;
+			float const SkiRestitution = 0.15f;
+
+			b2BodyDef bd;
+			bd.type = b2_dynamicBody;
+
+			float initial_y = BodyHeight / 2 + SkiThickness;
+			bd.position.Set(-m_platform_width / 2, initial_y);
+
+			b2Body* skier = m_world->CreateBody(&bd);
+
+			b2PolygonShape ski;
+			b2Vec2 verts[4];
+			verts[0].Set(-SkiLength / 2 - SkiThickness, -BodyHeight / 2);
+			verts[1].Set(-SkiLength / 2, -BodyHeight / 2 - SkiThickness);
+			verts[2].Set(SkiLength / 2, -BodyHeight / 2 - SkiThickness);
+			verts[3].Set(SkiLength / 2 + SkiThickness, -BodyHeight / 2);
+			ski.Set(verts, 4);
+
+			b2FixtureDef fd;
+			fd.density = 1.0f;
+
+			fd.friction = SkiFriction;
+			fd.restitution = SkiRestitution;
+
+			fd.shape = &ski;
+			skier->CreateFixture(&fd);
+
+			skier->SetLinearVelocity(b2Vec2(0.5f, 0.0f));
+
+			m_skier = skier;
+		}
+
+		g_camera.m_center = b2Vec2(m_platform_width / 2.0f, 0.0f);
+		g_camera.m_zoom = 0.4f;
+		m_fixed_camera = true;
+	}
+
+	void Keyboard(int key) override
+	{
+		switch (key)
+		{
+			case GLFW_KEY_C:
+			m_fixed_camera = !m_fixed_camera;
+			if(m_fixed_camera)
+			{
+				g_camera.m_center = b2Vec2(m_platform_width / 2.0f, 0.0f);
+			}
+			break;
+		}
+	}
+
+	void Step(Settings& settings) override
+	{
+		g_debugDraw.DrawString(5, m_textLine, "Keys: c = Camera fixed/tracking");
+		m_textLine += m_textIncrement;
+
+		if(!m_fixed_camera)
+		{
+			g_camera.m_center = m_skier->GetPosition();
+		}
+
+		Test::Step(settings);
+	}
+
+	static Test* Create()
+	{
+		return new Skier;
+	}
+
+	b2Body* m_skier;
+	float m_platform_width;
+	bool m_fixed_camera;
+};
+
+static int testIndex = RegisterTest("Bugs", "Skier", Skier::Create);