Difference between revisions of "Procedurally generated geometry tutorial"

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−
 
 
== Due to the current changes in the Horde API this tutorial will be delayed ==
 
== Due to the current changes in the Horde API this tutorial will be delayed ==
  
Line 27: Line 26:
 
<source lang="cpp" line="1">
 
<source lang="cpp" line="1">
 
#pragma once
 
#pragma once
 +
#include <sstream>
 +
#include <string>
 +
#include <iostream>
 +
 +
class StreamGenerator
 +
{
 +
public:
 +
StreamGenerator();
 +
virtual ~StreamGenerator();
 +
virtual const char* getStream() = 0;
 +
virtual const int getStreamSize() = 0;
 +
};
 +
</source>
 +
}}
 +
 +
{{CppSourceCode|
 +
description= StreamGenerator.h|
 +
code=
 +
<source lang="cpp" line="1">
 +
#include "StreamGenerator.cpp"
 +
 +
 +
 +
StreamGenerator::StreamGenerator()
 +
 +
{
 +
 +
 +
 +
}
  
  
  
−
#include <sstream>
+
StreamGenerator::~StreamGenerator()
 +
 
 +
{
 +
 
 +
 
 +
 
 +
}
 +
</source>
 +
}}
 +
 
 +
{{CppSourceCode|
 +
description= GeometryStreamGenerator.h|
 +
code=
 +
<source lang="cpp" line="1">
 +
#pragma once
 +
 
 +
 
  
−
#include <string>
+
#include "StreamGenerator.h"
  
−
#include <iostream>
+
#include "CustomGeometry.h"
  
  
  
−
class StreamGenerator  
+
class GeometryStreamGenerator : public StreamGenerator
  
 
{
 
{
 +
 +
private:
 +
 +
std::stringstream* ss;
 +
 +
void generate();
 +
 +
int numVertices, numTriangleIndices;
 +
 +
char* _stream;
 +
 +
CustomGeometry* _geom;
  
  
Line 46: Line 103:
 
public:
 
public:
  
−
StreamGenerator();
+
GeometryStreamGenerator(CustomGeometry* geom_);
 +
 
 +
~GeometryStreamGenerator();
 +
 
 +
const char* getStream();
 +
 
 +
const std::stringstream* getStringStream() { return ss; };
 +
 
 +
const int getStreamSize();
  
−
virtual ~StreamGenerator();
+
const int getNumVertices();
  
−
virtual const char* getStream() = 0;
+
const int getNumTriangleIndices();
  
−
virtual const int getStreamSize() = 0;
+
void release();
  
 
};
 
};
 +
 
</source>
 
</source>
 
}}
 
}}
 +
 +
{{CppSourceCode|
 +
description= GeometryStreamGenerator.cpp|
 +
code=
 +
<source lang="cpp" line="1">
 +
#include "GeometryStreamGenerator.h"
 +
 +
#include "time.h"
 +
 +
#include "utMath.h"
 +
 +
 +
 +
GeometryStreamGenerator::GeometryStreamGenerator(CustomGeometry* geom_) : _geom(geom_)
 +
 +
{
 +
 +
ss = new std::stringstream();
 +
 +
generate();
 +
 +
}
 +
 +
 +
 +
GeometryStreamGenerator::~GeometryStreamGenerator()
 +
 +
{
 +
 +
}
 +
 +
 +
 +
void GeometryStreamGenerator::generate()
 +
 +
{
 +
 +
numVertices = _geom->getNumVertices();
 +
 +
numTriangleIndices = _geom->getNumTriangleIndices();
 +
 +
 +
 +
const std::string _magicHeader = "H3DG";
 +
 +
const int _version = 5;
 +
 +
const int _numJoints = 1;
 +
 +
const float _identityMatrix[] = { 1.0f, 0.0f, 0.0f, 0.0f, 
 +
 +
0.0f, 1.0f, 0.0f, 0.0f, 
 +
 +
0.0f, 0.0f, 1.0f, 0.0f, 
 +
 +
0.0f, 0.0f, 0.0f, 1.0f};
 +
 +
const int _numVertexStreams = 3;
 +
 +
const int _magicVertices = 0;
 +
 +
const int _vertexStreamElementSize = 12;
 +
 +
const float* _positions = _geom->getPositions();
 +
 +
const int _magicNormals = 1;
 +
 +
const int _normalsStreamElementSize = 6;
 +
 +
const float* _normals = _geom->getNormals();
 +
 +
const int _magicTextureCoords1 = 6;
 +
 +
const int _texCoordStreamElementSize = 8;
 +
 +
const float* _texCoords = _geom->getTexCoords();
 +
 +
const int* _triangleIndices = _geom->getTriangleIndices();
 +
 +
const int _numMorphTragets = 0;
 +
 +
 +
 +
// header
 +
 +
ss->write(_magicHeader.c_str(), 4*sizeof(char));
 +
 +
ss->write((char*)&_version, sizeof(int));
 +
 +
// joints (mandatory)
 +
 +
ss->write((char*)&_numJoints, sizeof(int));
 +
 +
for (int i=0; i<16; ++i) {
 +
 +
ss->write((char*)&_identityMatrix[i], sizeof(float));
 +
 +
}
 +
 +
// vertices
 +
 +
ss->write((char*)&_numVertexStreams, sizeof(int));
 +
 +
const int numVerts = _geom->getNumVertices();
 +
 +
ss->write((char*)&numVerts, sizeof(int));
 +
 +
ss->write((char*)&_magicVertices, sizeof(int));
 +
 +
ss->write((char*)&_vertexStreamElementSize, sizeof(int));
 +
 +
for (int i=0; i<_geom->getNumVertices()*3; ++i) {
 +
 +
ss->write((char*)&_positions[i], sizeof(float));
 +
 +
}
 +
 +
// normals
 +
 +
ss->write((char*)&_magicNormals, sizeof(int));
 +
 +
ss->write((char*)&_normalsStreamElementSize, sizeof(int));
 +
 +
for (int i=0; i<_geom->getNumVertices()*3; ++i) {
 +
 +
// do not forget to mutliply the value with 32767 and
 +
 +
// then convert it to short before writing to the stream
 +
 +
const short f = (short)(_normals[i]*32767);
 +
 +
ss->write((char*)&f, sizeof(short));
 +
 +
}
 +
 +
// texture coordinates
 +
 +
ss->write((char*)&_magicTextureCoords1, sizeof(int));
 +
 +
ss->write((char*)&_texCoordStreamElementSize, sizeof(int));
 +
 +
for (int i=0; i<_geom->getNumVertices()*2; ++i) {
 +
 +
ss->write((char*)&_texCoords[i], sizeof(float));
 +
 +
}
 +
 +
// triangle indices
 +
 +
const int numTriangleIndices = _geom->getNumTriangleIndices();
 +
 +
ss->write((char*)&numTriangleIndices, sizeof(int));
 +
 +
for (int i=0; i<_geom->getNumTriangleIndices(); ++i) {
 +
 +
ss->write((char*)&_triangleIndices[i], sizeof(int));
 +
 +
}
 +
 +
ss->write((char*)&_numMorphTragets, sizeof(int));
 +
 +
 +
 +
_stream = new char[ss->tellp()];
 +
 +
ss->read(_stream, ss->tellp());
 +
 +
}
 +
 +
 +
 +
const char* GeometryStreamGenerator::getStream()
 +
 +
{
 +
 +
return _stream;
 +
 +
}
 +
 +
 +
 +
const int GeometryStreamGenerator::getStreamSize()
 +
 +
{
 +
 +
int t = (int)ss->tellp();
 +
 +
return t;
 +
 +
}
 +
 +
 +
 +
const int GeometryStreamGenerator::getNumVertices()
 +
 +
{
 +
 +
return numVertices;
 +
 +
}
 +
 +
 +
 +
const int GeometryStreamGenerator::getNumTriangleIndices()
 +
 +
{
 +
 +
return numTriangleIndices;
 +
 +
}
 +
 +
 +
 +
void GeometryStreamGenerator::release()
 +
 +
{
 +
 +
ss->flush();
 +
 +
ss->clear();
 +
 +
delete ss;
 +
 +
ss = 0;
 +
 +
delete[] _stream;
 +
 +
_stream = 0;
 +
 +
}
 +
</source>
 +
}}
 +
  
 
=CustomGeometry base class=
 
=CustomGeometry base class=

Revision as of 12:35, 26 October 2009

Due to the current changes in the Horde API this tutorial will be delayed

Work in progress


Important notes

  • The code used here has been tested with Horde3D 1.0.0 beta2 and beta3 and will NOT work with the latest release (beta4)


Overview

Basic approach

To create and display a procedurally generated mesh that, instead of being loaded from a Horde3D Scene node and a geoemtry file(*.scene.xml, *.geo), will be created in-memory by some algorithm, you have to create a mesh first and then "fake" the .geo-file and the scene node itself and pass it to the engine.

To do that you have to create your procedural geometry first. This is easy for simple shapes like single triangles, squares or triangle-strips, but will become way more difficult when we try to generate complex meshes, e.g. when we have a cloud of points in 3D space and have to describe which points make triangles, and which don't (calculating the triangle indices, texture coordinates and normals).

When we have calculated the geometry itself we need to create a char-stream to make Horde believe the geometry has been read from a file and pass it to Horde as a geometry Resource. The final step is to create a Horde3D Scene Node from our procedurally generated mesh and render it into our scene. [musicracer_intro.jpg This is how it could look like]

StreamGenerator

StreamGenerator.h 
#pragma once
#include <sstream>
#include <string>
#include <iostream>

class StreamGenerator 
{
public:
	StreamGenerator();
	virtual ~StreamGenerator();
	virtual const char* getStream() = 0;
	virtual const int getStreamSize() = 0;
};
StreamGenerator.h 
#include "StreamGenerator.cpp"



StreamGenerator::StreamGenerator() 

{



}



StreamGenerator::~StreamGenerator()

{



}
GeometryStreamGenerator.h 
#pragma once



#include "StreamGenerator.h"

#include "CustomGeometry.h"



class GeometryStreamGenerator : public StreamGenerator

{

private:

	std::stringstream* ss;

	void generate();

	int numVertices, numTriangleIndices;

	char* _stream;

	CustomGeometry* _geom;



public:

	GeometryStreamGenerator(CustomGeometry* geom_);

	~GeometryStreamGenerator();

	const char* getStream();

	const std::stringstream* getStringStream() { return ss; };

	const int getStreamSize();

	const int getNumVertices();

	const int getNumTriangleIndices();

	void release();

};
GeometryStreamGenerator.cpp 
#include "GeometryStreamGenerator.h"

#include "time.h"

#include "utMath.h"



GeometryStreamGenerator::GeometryStreamGenerator(CustomGeometry* geom_) : _geom(geom_)

{

	ss = new std::stringstream();

	generate();

}



GeometryStreamGenerator::~GeometryStreamGenerator()

{

}



void GeometryStreamGenerator::generate()

{

	numVertices = _geom->getNumVertices();

	numTriangleIndices = _geom->getNumTriangleIndices();



	const std::string _magicHeader = "H3DG";

	const int _version = 5;

	const int _numJoints = 1;

	const float _identityMatrix[] = {	1.0f, 0.0f, 0.0f, 0.0f,  

										0.0f, 1.0f, 0.0f, 0.0f,  

										0.0f, 0.0f, 1.0f, 0.0f,  

										0.0f, 0.0f, 0.0f, 1.0f};

	const int _numVertexStreams = 3;

	const int _magicVertices = 0;

	const int _vertexStreamElementSize = 12;

	const float* _positions = _geom->getPositions();

	const int _magicNormals = 1;

	const int _normalsStreamElementSize = 6;

	const float* _normals = _geom->getNormals();

	const int _magicTextureCoords1 = 6;

	const int _texCoordStreamElementSize = 8;

	const float* _texCoords = _geom->getTexCoords();

	const int* _triangleIndices = _geom->getTriangleIndices();

	const int _numMorphTragets = 0;



	// header

	ss->write(_magicHeader.c_str(), 4*sizeof(char));

	ss->write((char*)&_version, sizeof(int));

	// joints (mandatory)

	ss->write((char*)&_numJoints, sizeof(int));

	for (int i=0; i<16; ++i) {

		ss->write((char*)&_identityMatrix[i], sizeof(float));

	}

	// vertices

	ss->write((char*)&_numVertexStreams, sizeof(int));

	const int numVerts = _geom->getNumVertices();

	ss->write((char*)&numVerts, sizeof(int));

	ss->write((char*)&_magicVertices, sizeof(int));

	ss->write((char*)&_vertexStreamElementSize, sizeof(int));

	for (int i=0; i<_geom->getNumVertices()*3; ++i) {

		ss->write((char*)&_positions[i], sizeof(float));

	}

	// normals

	ss->write((char*)&_magicNormals, sizeof(int));

	ss->write((char*)&_normalsStreamElementSize, sizeof(int));

	for (int i=0; i<_geom->getNumVertices()*3; ++i) {

		// do not forget to mutliply the value with 32767 and 

		// then convert it to short before writing to the stream

		const short f = (short)(_normals[i]*32767);

		ss->write((char*)&f, sizeof(short));

	}

	// texture coordinates

	ss->write((char*)&_magicTextureCoords1, sizeof(int));

	ss->write((char*)&_texCoordStreamElementSize, sizeof(int));

	for (int i=0; i<_geom->getNumVertices()*2; ++i) {

		ss->write((char*)&_texCoords[i], sizeof(float));

	}

	// triangle indices

	const int numTriangleIndices = _geom->getNumTriangleIndices();

	ss->write((char*)&numTriangleIndices, sizeof(int));

	for (int i=0; i<_geom->getNumTriangleIndices(); ++i) {

		ss->write((char*)&_triangleIndices[i], sizeof(int));

	}

	ss->write((char*)&_numMorphTragets, sizeof(int));



	_stream = new char[ss->tellp()];

	ss->read(_stream, ss->tellp());

}



const char* GeometryStreamGenerator::getStream()

{

	return _stream;

}



const int GeometryStreamGenerator::getStreamSize() 

{

	int t = (int)ss->tellp();

	return t;

}



const int GeometryStreamGenerator::getNumVertices()

{

	return numVertices;

}



const int GeometryStreamGenerator::getNumTriangleIndices()

{

	return numTriangleIndices;

}



void GeometryStreamGenerator::release()

{

	ss->flush();

	ss->clear();

	delete ss;

	ss = 0;

	delete[] _stream;

	_stream = 0;

}


CustomGeometry base class

Simple Square

Simple Grid

Usage example

Retrieved from "http://horde3d.org/wiki/index.php?title=Procedurally_generated_geometry_tutorial&oldid=558"