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Work on raycasting.

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This commit is contained in:
David Williams 2011-01-08 17:31:42 +00:00
parent 8df20f2203
commit b607653e9f
2 changed files with 55 additions and 15 deletions
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15
library/PolyVoxCore/include/Raycast.h
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@ -26,21 +26,24 @@ freely, subject to the following restrictions:
namespace PolyVox
{
struct RaycastResult
{
bool foundIntersection;
Vector3DInt16 intersectionVoxel;
};
template <typename VoxelType>
class Raycast
{
public:
Raycast(Volume<VoxelType>* volData, const Vector3DFloat& v3dStart, const Vector3DFloat& v3dDirection, float fMaxDistance = 1000.0f);
Raycast(Volume<VoxelType>* volData, const Vector3DFloat& v3dStart, const Vector3DFloat& v3dDirection, RaycastResult& result);
void execute();
int x;
int y;
int z;
bool hit;
RaycastResult& m_result;
private:
bool doRaycast(float x1, float y1, float z1, float x2, float y2, float z2);
void doRaycast(float x1, float y1, float z1, float x2, float y2, float z2);
Volume<VoxelType>* m_volData;
VolumeSampler<VoxelType> m_sampVolume;

55
library/PolyVoxCore/include/Raycast.inl
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@ -23,25 +23,61 @@ freely, subject to the following restrictions:
namespace PolyVox
{
template <typename VoxelType>
Raycast<VoxelType>::Raycast(Volume<VoxelType>* volData, const Vector3DFloat& v3dStart, const Vector3DFloat& v3dDirection, float fMaxDistance)
Raycast<VoxelType>::Raycast(Volume<VoxelType>* volData, const Vector3DFloat& v3dStart, const Vector3DFloat& v3dDirection, RaycastResult& result)
:m_volData(volData)
,m_sampVolume(volData)
,m_v3dStart(v3dStart)
,m_v3dDirection(v3dDirection)
,m_fMaxDistance(fMaxDistance)
,m_result(result)
{
}
template <typename VoxelType>
void Raycast<VoxelType>::execute(void)
{
//The doRaycast function is assuming that it is iterating over the areas defined between
//voxels. We actually want to define the areas as being centered on voxels (as this is
//what the CubicSurfaceExtractor generates). We add (0.5,0.5,0.5) here to adjust for this.
Vector3DFloat v3dStart = m_v3dStart + Vector3DFloat(0.5f, 0.5f, 0.5f);
//Compute the end point
Vector3DFloat v3dEnd = v3dStart + m_v3dDirection;
hit = doRaycast(v3dStart.getX(), v3dStart.getY(), v3dStart.getZ(), v3dEnd.getX(), v3dEnd.getY(), v3dEnd.getZ());
//Do the raycast
doRaycast(v3dStart.getX(), v3dStart.getY(), v3dStart.getZ(), v3dEnd.getX(), v3dEnd.getY(), v3dEnd.getZ());
}
// This function is based on Christer Ericson's code and description of the 'Uniform Grid Intersection Test' in
// 'Real Time Collision Detection'. The following information from the errata on the book website is also relevent:
//
// pages 326-327. In the function VisitCellsOverlapped() the two lines calculating tx and ty are incorrect.
// The less-than sign in each line should be a greater-than sign. That is, the two lines should read:
//
// float tx = ((x1 > x2) ? (x1 - minx) : (maxx - x1)) / Abs(x2 - x1);
// float ty = ((y1 > y2) ? (y1 - miny) : (maxy - y1)) / Abs(y2 - y1);
//
// Thanks to Jetro Lauha of Fathammer in Helsinki, Finland for reporting this error.
//
// Jetro also points out that the computations of i, j, iend, and jend are incorrectly rounded if the line
// coordinates are allowed to go negative. While that was not really the intent of the code — that is, I
// assumed grids to be numbered from (0, 0) to (m, n) — I'm at fault for not making my assumption clear.
// Where it is important to handle negative line coordinates the computation of these variables should be
// changed to something like this:
//
// // Determine start grid cell coordinates (i, j)
// int i = (int)floorf(x1 / CELL_SIDE);
// int j = (int)floorf(y1 / CELL_SIDE);
//
// // Determine end grid cell coordinates (iend, jend)
// int iend = (int)floorf(x2 / CELL_SIDE);
// int jend = (int)floorf(y2 / CELL_SIDE);
//
// page 328. The if-statement that reads "if (ty <= tx && ty <= tz)" has a superfluous condition.
// It should simply read "if (ty <= tz)".
//
// This error was reported by Joey Hammer (PixelActive).
template <typename VoxelType>
bool Raycast<VoxelType>::doRaycast(float x1, float y1, float z1, float x2, float y2, float z2)
void Raycast<VoxelType>::doRaycast(float x1, float y1, float z1, float x2, float y2, float z2)
{
int i = (int)floorf(x1);
int j = (int)floorf(y1);
@ -72,10 +108,9 @@ namespace PolyVox
{
if(m_sampVolume.getVoxel().getDensity() > VoxelType::getThreshold())
{
x = i;
y = j;
z = k;
return true;
m_result.foundIntersection = true;
m_result.intersectionVoxel = Vector3DInt16(i,j,k);
return;
}
if(tx <= ty && tx <= tz)
@ -105,6 +140,8 @@ namespace PolyVox
}
}
return false;
//Didn't hit anything
m_result.foundIntersection = false;
m_result.intersectionVoxel = Vector3DInt16(0,0,0);
}
}