Box2DExample
Box2D "Bridge" example
Description
Example of usage Box2D a 2D physics engine with U++.
Result
main.cpp
#include <CtrlLib/CtrlLib.h>
#include <Painter/Painter.h>
#include <plugin/box2d/Box2D.h>
using namespace Upp;
struct QueryCallback : b2QueryCallback
{
QueryCallback(const b2Vec2& point)
{
this->point = point;
fixture = NULL;
}
bool ReportFixture(b2Fixture* fixture)
{
b2Body* body = fixture->GetBody();
if (body->GetType() == b2_dynamicBody)
{
bool inside = fixture->TestPoint(point);
if (inside)
{
this->fixture = fixture;
return false;
}
}
return true;
}
b2Vec2 point;
b2Fixture* fixture;
};
struct DebugDraw : b2Draw
{
Draw* w;
Sizef sz;
float cx, cy;
float aspect;
float zoom;
DebugDraw()
{}
void Init(Draw& d, Size s)
{
w = &d;
sz = s;
zoom = 15.0f;
cx = float(sz.cx / 2.0f);
cy = float(sz.cy / 2.0f + 150.0f);
aspect = float(sz.cx / sz.cy);
aspect *= zoom;
}
Point conv(const b2Vec2& v)
{
return Point(int(v.x * aspect + cx), int(cy - v.y * aspect));
}
b2Vec2 conv(const Point& p)
{
b2Vec2 v;
v.x = (p.x - cx) / aspect;
v.y = (cy - p.y) / aspect;
return v;
}
Color conv(const b2Color& c, double f = 255.0)
{
return Color(int(c.r * f), int(c.g * f), int(c.b * f));
}
virtual void DrawPolygon(const b2Vec2* v, int32 vertexCount, const b2Color& color)
{
Vector<Point> p;
p.SetCount(vertexCount + 1);
for(int i = 0; i < vertexCount; ++i)
p[i] = conv(v[i]);
p[vertexCount] = p[0];
w->DrawPolyline(p, 1, conv(color, 150.0));
}
virtual void DrawSolidPolygon(const b2Vec2* v, int32 vertexCount, const b2Color& color)
{
Vector<Point> p;
p.SetCount(vertexCount);
for(int i = 0; i < vertexCount; ++i)
p[i] = conv(v[i]);
w->DrawPolygon(p, conv(color, 255.0), 1, conv(color, 150));
}
virtual void DrawCircle(const b2Vec2& center, float radius, const b2Color& color)
{
int r = int(aspect * radius * 2.0f);
// int r = int(radius * 2.0f);
Point p = conv(b2Vec2(center.x - radius, center.y + radius));
w->DrawEllipse(p.x, p.y, r, r, conv(color, 150.0));
}
virtual void DrawSolidCircle(const b2Vec2& center, float radius, const b2Vec2& axis, const b2Color& color)
{
int r = int(aspect * radius * 2.0f);
Point p = conv(b2Vec2(center.x - radius, center.y + radius));
w->DrawEllipse(p.x, p.y, r, r, conv(color, 255.0), PEN_SOLID, conv(color, 150.0));
}
virtual void DrawSegment(const b2Vec2& p1, const b2Vec2& p2, const b2Color& color)
{
w->DrawLine(conv(p1), conv(p2), 1, conv(color, 150.0));
}
virtual void DrawTransform(const b2Transform& xf)
{
}
virtual void DrawPoint(const b2Vec2& p0, float size, const b2Color& color)
{
Point p = conv(p0);
// int s = int(size * aspect);
int s = int(size);
w->DrawRect(p.x, p.y, s, s, conv(color, 255.0));
}
void DrawString(int x, int y, const char* string, ...)
{
char buffer[256];
va_list arg;
va_start(arg, string);
vsprintf(buffer, string, arg);
va_end(arg);
w->DrawText(x, y, buffer);
}
void DrawAABB(b2AABB* aabb, const b2Color& color)
{
Point lb = conv(aabb->lowerBound);
Point ub = conv(aabb->upperBound);
Color fg = conv(color, 150.0);
w->DrawRect(lb.x, lb.y, ub.x, ub.y, fg);
}
};
struct App : TopWindow
{
b2World world;
b2MouseJoint* mouseJoint;
b2Vec2 mouseWorld;
b2Body* groundBody;
Option showBoxes;
DropList drawMode;
DebugDraw debugDraw;
typedef App CLASSNAME;
App() : world(b2Vec2(0.0, -10.0))
{
Title("Box2D Example");
SetRect(0, 0, Zx(640), Zy(480));
Sizeable().Zoomable();
BackPaint();
SetTimeCallback(-1, THISBACK(Render));
mouseJoint = NULL;
b2Vec2 gravity;
gravity.Set(0.0f, -10.0f);
world.SetGravity(gravity);
world.SetDebugDraw(&debugDraw);
b2BodyDef bodyDef;
groundBody = world.CreateBody(&bodyDef);
showBoxes.SetLabel("AABBs");
drawMode
.Add(0, "Draw")
.Add(1, "Painter - No aa")
.Add(2, "Painter - Antialiased")
.Add(3, "Painter - Subpixel");
drawMode <<= 2;
Add(showBoxes.LeftPosZ(5, 55).TopPosZ(5, 19));
Add(drawMode.LeftPosZ(5, 130).TopPosZ(28, 19));
Bridge();
}
void Bridge()
{
const int e_count = 30;
b2Body* ground = NULL;
{
b2BodyDef bd;
ground = world.CreateBody(&bd);
b2EdgeShape shape;
shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
ground->CreateFixture(&shape, 0.0f);
}
{
b2PolygonShape shape;
shape.SetAsBox(0.5f, 0.125f);
b2FixtureDef fd;
fd.shape = &shape;
fd.density = 20.0f;
fd.friction = 0.2f;
b2RevoluteJointDef jd;
b2Body* prevBody = ground;
for (int32 i = 0; i < e_count; ++i)
{
b2BodyDef bd;
bd.type = b2_dynamicBody;
bd.position.Set(-14.5f + 1.0f * i, 5.0f);
b2Body* body = world.CreateBody(&bd);
body->CreateFixture(&fd);
b2Vec2 anchor(-15.0f + 1.0f * i, 5.0f);
jd.Initialize(prevBody, body, anchor);
world.CreateJoint(&jd);
prevBody = body;
}
b2Vec2 anchor(-15.0f + 1.0f * e_count, 5.0f);
jd.Initialize(prevBody, ground, anchor);
world.CreateJoint(&jd);
}
for (int32 i = 0; i < 2; ++i)
{
b2Vec2 vertices[3];
vertices[0].Set(-0.5f, 0.0f);
vertices[1].Set(0.5f, 0.0f);
vertices[2].Set(0.0f, 1.5f);
b2PolygonShape shape;
shape.Set(vertices, 3);
b2FixtureDef fd;
fd.shape = &shape;
fd.density = 1.0f;
b2BodyDef bd;
bd.type = b2_dynamicBody;
bd.position.Set(-8.0f + 8.0f * i, 12.0f);
b2Body* body = world.CreateBody(&bd);
body->CreateFixture(&fd);
}
for (int32 i = 0; i < 3; ++i)
{
b2CircleShape shape;
shape.m_radius = 0.5f;
b2FixtureDef fd;
fd.shape = &shape;
fd.density = 1.0f;
b2BodyDef bd;
bd.type = b2_dynamicBody;
bd.position.Set(-6.0f + 6.0f * i, 10.0f);
b2Body* body = world.CreateBody(&bd);
body->CreateFixture(&fd);
}
}
void Render() { Refresh(); }
virtual void Paint(Draw& w)
{
int m = ~drawMode;
float hz = 60;
int velocityIterations = 8;
int positionIterations = 10;
float timeStep = 1.0f / hz;
int flags = b2Draw::e_shapeBit | b2Draw::e_jointBit;
if(showBoxes)
flags |= b2Draw::e_aabbBit;
debugDraw.SetFlags(flags);
world.SetWarmStarting(1);
world.SetContinuousPhysics(1);
world.Step(timeStep, velocityIterations, positionIterations);
Point p1, p2;
if(mouseJoint)
{
p1 = debugDraw.conv(mouseJoint->GetAnchorB());
p2 = debugDraw.conv(mouseJoint->GetTarget());
}
Size sz = GetSize();
if(m > 0)
{
ImageBuffer ib(sz);
BufferPainter bp(ib, m == 1 ? MODE_NOAA : m == 2 ? MODE_ANTIALIASED : MODE_SUBPIXEL);
RGBA bg;
bg.r = bg.g = bg.b = bg.a = 255;
bp.Clear(bg);
debugDraw.Init(bp, sz);
world.DebugDraw();
if(mouseJoint)
{
bp.DrawLine(p1, p2, 2, LtGreen);
bp.DrawEllipse(p2.x - 3, p2.y - 3, 6, 6, Green, PEN_SOLID, Black);
}
w.DrawImage(0, 0, ib);
}
else
{
w.DrawRect(sz, White);
debugDraw.Init(w, sz);
world.DebugDraw();
if(mouseJoint)
{
w.DrawLine(p1, p2, 2, LtGreen);
w.DrawEllipse(p2.x - 3, p2.y - 3, 6, 6, Green, PEN_SOLID, Black);
}
}
}
virtual void LeftDown(Point p0, dword keyflags)
{
b2Vec2 p = debugDraw.conv(p0);
mouseWorld = p;
if(mouseJoint != NULL)
return;
b2AABB aabb;
b2Vec2 d;
d.Set(0.001f, 0.001f);
aabb.lowerBound = p - d;
aabb.upperBound = p + d;
QueryCallback callback(p);
world.QueryAABB(&callback, aabb);
if (callback.fixture)
{
b2Body* body = callback.fixture->GetBody();
b2MouseJointDef md;
md.bodyA = groundBody;
md.bodyB = body;
md.target = p;
md.maxForce = 1000.0f * body->GetMass();
mouseJoint = (b2MouseJoint*) world.CreateJoint(&md);
body->SetAwake(true);
}
}
virtual void LeftUp(Point p0, dword keyflags)
{
if (mouseJoint)
{
world.DestroyJoint(mouseJoint);
mouseJoint = NULL;
}
}
virtual void MouseMove(Point p, dword keyflags)
{
mouseWorld = debugDraw.conv(p);
if(mouseJoint)
mouseJoint->SetTarget(mouseWorld);
}
virtual void MouseWheel(Point p, int zdelta, dword keyflags)
{
debugDraw.zoom += zdelta / 80.0f;
}
};
GUI_APP_MAIN
{
App().Run();
}
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