155 lines
7.1 KiB
C++
155 lines
7.1 KiB
C++
/*******************************************************************************
|
|
* The MIT License (MIT)
|
|
*
|
|
* Copyright (c) 2015 David Williams and Matthew Williams
|
|
*
|
|
* Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
* of this software and associated documentation files (the "Software"), to deal
|
|
* in the Software without restriction, including without limitation the rights
|
|
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
* copies of the Software, and to permit persons to whom the Software is
|
|
* furnished to do so, subject to the following conditions:
|
|
*
|
|
* The above copyright notice and this permission notice shall be included in all
|
|
* copies or substantial portions of the Software.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
|
* SOFTWARE.
|
|
*******************************************************************************/
|
|
|
|
#ifndef __PolyVox_MarchingCubesController_H__
|
|
#define __PolyVox_MarchingCubesController_H__
|
|
|
|
#include "BaseVolume.h"
|
|
|
|
#include <limits>
|
|
|
|
namespace PolyVox
|
|
{
|
|
/**
|
|
* This class provides a default implementation of a controller for the MarchingCubesSurfaceExtractor. It controls the behaviour of the
|
|
* MarchingCubesSurfaceExtractor and provides the required properties from the underlying voxel type.
|
|
*
|
|
* PolyVox does not enforce any requirements regarding what data must be present in a voxel, and instead allows any primitive or user-defined
|
|
* type to be used. However, the Marching Cubes algorithm does have some requirents about the underlying data in that conceptually it operates
|
|
* on a <i>density field</i>. In addition, the PolyVox implementation of the Marching Cubes algorithm also understands the idea of each voxel
|
|
* having a material which is copied into the vertex data.
|
|
*
|
|
* Because we want the MarchingCubesSurfaceExtractor to work on <i>any</i> voxel type, we use a <i>Marching Cubes controller</i> (passed as
|
|
* a parameter of the MarchingCubesSurfaceExtractor) to expose the required properties. This parameter defaults to the DefaultMarchingCubesController.
|
|
* The main implementation of this class is designed to work with primitives data types, and the class is also specialised for the Material,
|
|
* Density and MaterialdensityPair classes.
|
|
*
|
|
* If you create a custom class for your voxel data then you probably want to include a specialisation of DefaultMarchingCubesController,
|
|
* though you don't have to if you don't want to use the Marching Cubes algorithm or if you prefer to define a seperate Marching Cubes controller
|
|
* and pass it as an explicit parameter (rather than relying on the default).
|
|
*
|
|
* For primitive types, the DefaultMarchingCubesController considers the value of the voxel to represent it's density and just returns a constant
|
|
* for the material. So you can, for example, run the MarchingCubesSurfaceExtractor on a volume of floats or ints.
|
|
*
|
|
* It is possible to customise the behaviour of the controller by providing a threshold value through the constructor. The extracted surface
|
|
* will pass through the density value specified by the threshold, and so you should make sure that the threshold value you choose is between
|
|
* the minimum and maximum values found in your volume data. By default it is in the middle of the representable range of the underlying type.
|
|
*
|
|
* \sa MarchingCubesSurfaceExtractor
|
|
*
|
|
*/
|
|
template<typename VoxelType>
|
|
class DefaultMarchingCubesController
|
|
{
|
|
public:
|
|
/// Used to inform the MarchingCubesSurfaceExtractor about which type it should use for representing densities.
|
|
typedef VoxelType DensityType;
|
|
/// Used to inform the MarchingCubesSurfaceExtractor about which type it should use for representing materials.
|
|
typedef VoxelType MaterialType;
|
|
|
|
/**
|
|
* Constructor
|
|
*
|
|
* This version of the constructor takes no parameters and sets the threshold to the middle of the representable range of the underlying type.
|
|
* For example, if the voxel type is 'uint8_t' then the representable range is 0-255, and the threshold will be set to 127. On the other hand,
|
|
* if the voxel type is 'float' then the representable range is -FLT_MAX to FLT_MAX and the threshold will be set to zero.
|
|
*/
|
|
DefaultMarchingCubesController(void)
|
|
{
|
|
if (std::is_signed<DensityType>())
|
|
{
|
|
m_tThreshold = DensityType(0);
|
|
}
|
|
else
|
|
{
|
|
m_tThreshold = (((std::numeric_limits<DensityType>::min)() + (std::numeric_limits<DensityType>::max)()) / 2);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Converts the underlying voxel type into a density value.
|
|
*
|
|
* The default implementation of this function just returns the voxel type directly and is suitable for primitives types. Specialisations of
|
|
* this class can modify this behaviour.
|
|
*/
|
|
DensityType convertToDensity(VoxelType voxel)
|
|
{
|
|
return voxel;
|
|
}
|
|
|
|
/**
|
|
* Converts the underlying voxel type into a material value.
|
|
*
|
|
* The default implementation of this function just returns the constant '1'. There's not much else it can do, as it needs to work with primitive
|
|
* types and the actual value of the type is already being considered to be the density. Specialisations of this class can modify this behaviour.
|
|
*/
|
|
MaterialType convertToMaterial(VoxelType /*voxel*/)
|
|
{
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* Returns a material which is in some sense a weighted combination of the supplied materials.
|
|
*
|
|
* The Marching Cubes algotithm generates vertices which lie between voxels, and ideally the material of the vertex should be interpolated from the materials
|
|
* of the voxels. In practice, that material type is often an integer identifier (e.g. 1 = rock, 2 = soil, 3 = grass) and an interpolation doean't make sense
|
|
* (e.g. soil is not a combination or rock and grass). Therefore this default interpolation just returns whichever material is associated with a voxel of the
|
|
* higher density, but if more advanced voxel types do support interpolation then it can be implemented in this function.
|
|
*/
|
|
MaterialType blendMaterials(VoxelType a, VoxelType b, float /*weight*/)
|
|
{
|
|
if(convertToDensity(a) > convertToDensity(b))
|
|
{
|
|
return convertToMaterial(a);
|
|
}
|
|
else
|
|
{
|
|
return convertToMaterial(b);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns the density value which was passed to the constructor.
|
|
*
|
|
* As mentioned in the class description, the extracted surface will pass through the density value specified by the threshold, and so you
|
|
* should make sure that the threshold value you choose is between the minimum and maximum values found in your volume data. By default it
|
|
* is in the middle of the representable range of the underlying type.
|
|
*/
|
|
DensityType getThreshold(void)
|
|
{
|
|
return m_tThreshold;
|
|
}
|
|
|
|
void setThreshold(DensityType tThreshold)
|
|
{
|
|
m_tThreshold = tThreshold;
|
|
}
|
|
|
|
private:
|
|
DensityType m_tThreshold;
|
|
};
|
|
}
|
|
|
|
#endif
|