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Tutorial 23: SMeshBufferHandling

A tutorial by geoff.

In this tutorial we'll learn how to create custom meshes and deal with them with Irrlicht. We'll create an interesting heightmap with some lighting effects. With keys 1,2,3 you can choose a different mesh layout, which is put into the mesh buffers as desired. All positions, normals, etc. are updated accordingly.

Ok, let's start with the headers (I think there's nothing to say about it)

#include <irrlicht.h>
#include "driverChoice.h"
#ifdef _MSC_VER
#pragma comment(lib, "Irrlicht.lib")
#endif
//Namespaces for the engine
using namespace irr;
using namespace video;
using namespace core;
using namespace scene;
using namespace io;
using namespace gui;
driverChoice.h
irrlicht.h
Main header file of the irrlicht, the only file needed to include.
irr::core
Basic classes such as vectors, planes, arrays, lists, and so on can be found in this namespace.
Definition aabbox3d.h:15
irr::gui
The gui namespace contains useful classes for easy creation of a graphical user interface.
Definition EGUIAlignment.h:11
irr::io
This namespace provides interfaces for input/output: Reading and writing files, accessing zip archive...
Definition EAttributes.h:11
irr::scene
All scene management can be found in this namespace: Mesh loading, special scene nodes like octrees a...
Definition CDynamicMeshBuffer.h:16
irr::video
The video namespace contains classes for accessing the video driver. All 2d and 3d rendering is done ...
Definition EDriverFeatures.h:11
irr
Everything in the Irrlicht Engine can be found in this namespace.
Definition aabbox3d.h:13

This is the type of the functions which work out the colour.

typedef SColor colour_func(f32 x, f32 y, f32 z);
irr::f32
float f32
32 bit floating point variable.
Definition irrTypes.h:104

Here comes a set of functions which can be used for coloring the nodes while creating the mesh.

// Greyscale, based on the height.
SColor grey(f32, f32, f32 z)
{
u32 n = (u32)(255.f * z);
return SColor(255, n, n, n);
}
// Interpolation between blue and white, with red added in one
// direction and green in the other.
SColor yellow(f32 x, f32 y, f32)
{
return SColor(255, 128 + (u32)(127.f * x), 128 + (u32)(127.f * y), 255);
}
// Pure white.
SColor white(f32, f32, f32) { return SColor(255, 255, 255, 255); }
irr::u32
unsigned int u32
32 bit unsigned variable.
Definition irrTypes.h:58

The type of the functions which generate the heightmap. x and y range between -0.5 and 0.5, and s is the scale of the heightmap.

typedef f32 generate_func(s16 x, s16 y, f32 s);
// An interesting sample function :-)
f32 eggbox(s16 x, s16 y, f32 s)
{
const f32 r = 4.f*sqrtf((f32)(x*x + y*y))/s;
const f32 z = expf(-r * 2) * (cosf(0.2f * x) + cosf(0.2f * y));
return 0.25f+0.25f*z;
}
// A rather dumb sine function :-/
f32 moresine(s16 x, s16 y, f32 s)
{
const f32 xx=0.3f*(f32)x/s;
const f32 yy=12*y/s;
const f32 z = sinf(xx*xx+yy)*sinf(xx+yy*yy);
return 0.25f + 0.25f * z;
}
// A simple function
f32 justexp(s16 x, s16 y, f32 s)
{
const f32 xx=6*x/s;
const f32 yy=6*y/s;
const f32 z = (xx*xx+yy*yy);
return 0.3f*z*cosf(xx*yy);
}
irr::s16
signed short s16
16 bit signed variable.
Definition irrTypes.h:48

A simple class for representing heightmaps. Most of this should be obvious.

class HeightMap
{
private:
const u16 Width;
const u16 Height;
f32 s;
core::array<f32> data;
public:
HeightMap(u16 _w, u16 _h) : Width(_w), Height(_h), s(0.f), data(0)
{
s = sqrtf((f32)(Width * Width + Height * Height));
data.set_used(Width * Height);
}
// Fill the heightmap with values generated from f.
void generate(generate_func f)
{
u32 i=0;
for(u16 y = 0; y < Height; ++y)
for(u16 x = 0; x < Width; ++x)
set(i++, calc(f, x, y));
}
u16 height() const { return Height; }
u16 width() const { return Width; }
f32 calc(generate_func f, u16 x, u16 y) const
{
const f32 xx = (f32)x - Width*0.5f;
const f32 yy = (f32)y - Height*0.5f;
return f((u16)xx, (u16)yy, s);
}
// The height at (x, y) is at position y * Width + x.
void set(u16 x, u16 y, f32 z) { data[y * Width + x] = z; }
void set(u32 i, f32 z) { data[i] = z; }
f32 get(u16 x, u16 y) const { return data[y * Width + x]; }
irr::core::array
Self reallocating template array (like stl vector) with additional features.
Definition irrArray.h:23
irr::core::array::set_used
void set_used(u32 usedNow)
Sets the size of the array and allocates new elements if necessary.
Definition irrArray.h:257
irr::u16
unsigned short u16
16 bit unsigned variable.
Definition irrTypes.h:40

The only difficult part. This considers the normal at (x, y) to be the cross product of the vectors between the adjacent points in the horizontal and vertical directions.

s is a scaling factor, which is necessary if the height units are different from the coordinate units; for example, if your map has heights in metres and the coordinates are in units of a kilometer.

vector3df getnormal(u16 x, u16 y, f32 s) const
{
const f32 zc = get(x, y);
f32 zl, zr, zu, zd;
if (x == 0)
{
zr = get(x + 1, y);
zl = zc + zc - zr;
}
else if (x == Width - 1)
{
zl = get(x - 1, y);
zr = zc + zc - zl;
}
else
{
zr = get(x + 1, y);
zl = get(x - 1, y);
}
if (y == 0)
{
zd = get(x, y + 1);
zu = zc + zc - zd;
}
else if (y == Height - 1)
{
zu = get(x, y - 1);
zd = zc + zc - zu;
}
else
{
zd = get(x, y + 1);
zu = get(x, y - 1);
}
return vector3df(s * 2 * (zl - zr), 4, s * 2 * (zd - zu)).normalize();
}
};
irr::core::vector3d::normalize
vector3d< T > & normalize()
Normalizes the vector.
Definition vector3d.h:168
irr::core::vector3df
vector3d< f32 > vector3df
Typedef for a f32 3d vector.
Definition vector3d.h:445

A class which generates a mesh from a heightmap.

class TMesh
{
private:
u16 Width;
u16 Height;
f32 Scale;
public:
SMesh* Mesh;
TMesh() : Mesh(0), Width(0), Height(0), Scale(1.f)
{
Mesh = new SMesh();
}
~TMesh()
{
Mesh->drop();
}
// Unless the heightmap is small, it won't all fit into a single
// SMeshBuffer. This function chops it into pieces and generates a
// buffer from each one.
void init(const HeightMap &hm, f32 scale, colour_func cf, IVideoDriver *driver)
{
Scale = scale;
const u32 mp = driver -> getMaximalPrimitiveCount();
Width = hm.width();
Height = hm.height();
const u32 sw = mp / (6 * Height); // the width of each piece
u32 i=0;
for(u32 y0 = 0; y0 < Height; y0 += sw)
{
u16 y1 = y0 + sw;
if (y1 >= Height)
y1 = Height - 1; // the last one might be narrower
addstrip(hm, cf, y0, y1, i);
++i;
}
if (i<Mesh->getMeshBufferCount())
{
// clear the rest
for (u32 j=i; j<Mesh->getMeshBufferCount(); ++j)
{
Mesh->getMeshBuffer(j)->drop();
}
Mesh->MeshBuffers.erase(i,Mesh->getMeshBufferCount()-i);
}
// set dirty flag to make sure that hardware copies of this
// buffer are also updated, see IMesh::setHardwareMappingHint
Mesh->setDirty();
Mesh->recalculateBoundingBox();
}
// Generate a SMeshBuffer which represents all the vertices and
// indices for values of y between y0 and y1, and add it to the
// mesh.
void addstrip(const HeightMap &hm, colour_func cf, u16 y0, u16 y1, u32 bufNum)
{
SMeshBuffer *buf = 0;
if (bufNum<Mesh->getMeshBufferCount())
{
buf = (SMeshBuffer*)Mesh->getMeshBuffer(bufNum);
}
else
{
// create new buffer
buf = new SMeshBuffer();
Mesh->addMeshBuffer(buf);
// to simplify things we drop here but continue using buf
buf->drop();
}
buf->Vertices.set_used((1 + y1 - y0) * Width);
u32 i=0;
for (u16 y = y0; y <= y1; ++y)
{
for (u16 x = 0; x < Width; ++x)
{
const f32 z = hm.get(x, y);
const f32 xx = (f32)x/(f32)Width;
const f32 yy = (f32)y/(f32)Height;
S3DVertex& v = buf->Vertices[i++];
v.Pos.set(x, Scale * z, y);
v.Normal.set(hm.getnormal(x, y, Scale));
v.Color=cf(xx, yy, z);
v.TCoords.set(xx, yy);
}
}
buf->Indices.set_used(6 * (Width - 1) * (y1 - y0));
i=0;
for(u16 y = y0; y < y1; ++y)
{
for(u16 x = 0; x < Width - 1; ++x)
{
const u16 n = (y-y0) * Width + x;
buf->Indices[i]=n;
buf->Indices[++i]=n + Width;
buf->Indices[++i]=n + Width + 1;
buf->Indices[++i]=n + Width + 1;
buf->Indices[++i]=n + 1;
buf->Indices[++i]=n;
++i;
}
}
buf->recalculateBoundingBox();
}
};
irr::scene::CMeshBuffer::Vertices
core::array< T > Vertices
Vertices of this buffer.
Definition CMeshBuffer.h:283
irr::scene::SMeshBuffer
CMeshBuffer< video::S3DVertex > SMeshBuffer
Standard meshbuffer.
Definition CMeshBuffer.h:291

Our event receiver implementation, taken from tutorial 4.

class MyEventReceiver : public IEventReceiver
{
public:
// This is the one method that we have to implement
virtual bool OnEvent(const SEvent& event)
{
// Remember whether each key is down or up
if (event.EventType == irr::EET_KEY_INPUT_EVENT)
KeyIsDown[event.KeyInput.Key] = event.KeyInput.PressedDown;
return false;
}
// This is used to check whether a key is being held down
virtual bool IsKeyDown(EKEY_CODE keyCode) const
{
return KeyIsDown[keyCode];
}
MyEventReceiver()
{
for (u32 i=0; i<KEY_KEY_CODES_COUNT; ++i)
KeyIsDown[i] = false;
}
private:
// We use this array to store the current state of each key
bool KeyIsDown[KEY_KEY_CODES_COUNT];
};
irr::IEventReceiver
Interface of an object which can receive events.
Definition IEventReceiver.h:434
irr::EKEY_CODE
EKEY_CODE
Definition Keycodes.h:12
irr::KEY_KEY_CODES_COUNT
@ KEY_KEY_CODES_COUNT
Definition Keycodes.h:168
irr::EET_KEY_INPUT_EVENT
@ EET_KEY_INPUT_EVENT
A key input event.
Definition IEventReceiver.h:35
irr::SEvent
SEvents hold information about an event. See irr::IEventReceiver for details on event handling.
Definition IEventReceiver.h:263
irr::SEvent::EventType
EEVENT_TYPE EventType
Definition IEventReceiver.h:414

Much of this is code taken from some of the examples. We merely set up a mesh from a heightmap, light it with a moving light, and allow the user to navigate around it.

int main(int argc, char* argv[])
{
// ask user for driver
video::E_DRIVER_TYPE driverType=driverChoiceConsole();
if (driverType==video::EDT_COUNT)
return 1;
MyEventReceiver receiver;
IrrlichtDevice* device = createDevice(driverType,
core::dimension2du(800, 600), 32, false, false, false,
&receiver);
if(device == 0)
return 1;
IVideoDriver *driver = device->getVideoDriver();
ISceneManager *smgr = device->getSceneManager();
device->setWindowCaption(L"Irrlicht Example for SMesh usage.");
irr::IrrlichtDevice
The Irrlicht device. You can create it with createDevice() or createDeviceEx().
Definition IrrlichtDevice.h:44
irr::IrrlichtDevice::setWindowCaption
virtual void setWindowCaption(const wchar_t *text)=0
Sets the caption of the window.
irr::IrrlichtDevice::getSceneManager
virtual scene::ISceneManager * getSceneManager()=0
Provides access to the scene manager.
irr::IrrlichtDevice::getVideoDriver
virtual video::IVideoDriver * getVideoDriver()=0
Provides access to the video driver for drawing 3d and 2d geometry.
irr::core::dimension2du
dimension2d< u32 > dimension2du
Typedef for an unsigned integer dimension.
Definition dimension2d.h:212
irr::video::E_DRIVER_TYPE
E_DRIVER_TYPE
An enum for all types of drivers the Irrlicht Engine supports.
Definition EDriverTypes.h:15
irr::video::EDT_COUNT
@ EDT_COUNT
No driver, just for counting the elements.
Definition EDriverTypes.h:56
irr::createDevice
IRRLICHT_API IrrlichtDevice *IRRCALLCONV createDevice(video::E_DRIVER_TYPE deviceType=video::EDT_SOFTWARE, const core::dimension2d< u32 > &windowSize=(core::dimension2d< u32 >(640, 480)), u32 bits=16, bool fullscreen=false, bool stencilbuffer=false, bool vsync=false, IEventReceiver *receiver=0)
Creates an Irrlicht device. The Irrlicht device is the root object for using the engine.

Create the custom mesh and initialize with a heightmap

TMesh mesh;
HeightMap hm = HeightMap(255, 255);
hm.generate(eggbox);
mesh.init(hm, 50.f, grey, driver);
// Add the mesh to the scene graph
IMeshSceneNode* meshnode = smgr -> addMeshSceneNode(mesh.Mesh);
meshnode->setMaterialFlag(video::EMF_BACK_FACE_CULLING, false);
// light is just for nice effects
ILightSceneNode *node = smgr->addLightSceneNode(0, vector3df(0,100,0),
SColorf(1.0f, 0.6f, 0.7f, 1.0f), 500.0f);
if (node)
{
node->getLightData().Attenuation.set(0.f, 1.f/500.f, 0.f);
ISceneNodeAnimator* anim = smgr->createFlyCircleAnimator(vector3df(0,150,0),250.0f);
if (anim)
{
node->addAnimator(anim);
anim->drop();
}
}
ICameraSceneNode* camera = smgr->addCameraSceneNodeFPS();
if (camera)
{
camera->setPosition(vector3df(-20.f, 150.f, -20.f));
camera->setTarget(vector3df(200.f, -80.f, 150.f));
camera->setFarValue(20000.0f);
}
irr::video::EMF_BACK_FACE_CULLING
@ EMF_BACK_FACE_CULLING
Is backface culling enabled? Default: true.
Definition EMaterialFlags.h:36

Just a usual render loop with event handling. The custom mesh is a usual part of the scene graph which gets rendered by drawAll.

while(device->run())
{
if(!device->isWindowActive())
{
device->sleep(100);
continue;
}
if(receiver.IsKeyDown(irr::KEY_KEY_W))
{
meshnode->setMaterialFlag(video::EMF_WIREFRAME, !meshnode->getMaterial(0).Wireframe);
}
else if(receiver.IsKeyDown(irr::KEY_KEY_1))
{
hm.generate(eggbox);
mesh.init(hm, 50.f, grey, driver);
}
else if(receiver.IsKeyDown(irr::KEY_KEY_2))
{
hm.generate(moresine);
mesh.init(hm, 50.f, yellow, driver);
}
else if(receiver.IsKeyDown(irr::KEY_KEY_3))
{
hm.generate(justexp);
mesh.init(hm, 50.f, yellow, driver);
}
driver->beginScene(true, true, SColor(0xff000000));
smgr->drawAll();
driver->endScene();
}
device->drop();
return 0;
}
irr::IReferenceCounted::drop
bool drop() const
Drops the object. Decrements the reference counter by one.
Definition IReferenceCounted.h:116
irr::IrrlichtDevice::run
virtual bool run()=0
Runs the device.
irr::IrrlichtDevice::sleep
virtual void sleep(u32 timeMs, bool pauseTimer=false)=0
Pause execution and let other processes to run for a specified amount of time.
irr::IrrlichtDevice::isWindowActive
virtual bool isWindowActive() const =0
Returns if the window is active.
irr::video::EMF_WIREFRAME
@ EMF_WIREFRAME
Draw as wireframe or filled triangles? Default: false.
Definition EMaterialFlags.h:17
irr::KEY_KEY_3
@ KEY_KEY_3
Definition Keycodes.h:59
irr::KEY_KEY_1
@ KEY_KEY_1
Definition Keycodes.h:57
irr::KEY_KEY_2
@ KEY_KEY_2
Definition Keycodes.h:58
irr::KEY_KEY_W
@ KEY_KEY_W
Definition Keycodes.h:88

That's it! Just compile and play around with the program.

- Irrlicht Engine Documentation © 2003-2012 by Nikolaus Gebhardt. Generated on for Irrlicht 3D Engine by Doxygen 1.15.0