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// Geometric Tools, LLC
// Copyright (c) 1998-2014
// Distributed under the Boost Software License, Version 1.0.
// http://www.boost.org/LICENSE_1_0.txt
// http://www.geometrictools.com/License/Boost/LICENSE_1_0.txt
//
// File Version: 5.0.0 (2010/01/01)
#include "RayTracer.h"
#include "Wm5Memory.h"
//----------------------------------------------------------------------------
RayTracer::RayTracer (Function F, Gradient DF, int width, int height)
:
Location(0.0f, 0.0f, 0.0f),
DVector(0.0f, 0.0f, 1.0f),
UVector(0.0f, 1.0f, 0.0f),
RVector(-1.0f, 0.0f, 0.0f),
Near(1.0f),
Far(10.0f),
HalfWidth(0.5f),
HalfHeight(0.5f),
Epsilon(1.0e-4f),
MaxBisectSteps(8),
mFunction(F),
mGradient(DF),
mWidth(width),
mHeight(height)
{
int numPixels = mWidth*mHeight;
mImage = new1<float>(numPixels);
mBlurredImage = new1<float>(numPixels);
size_t numBytes = numPixels*sizeof(float);
memset(mImage, 0, numBytes);
memset(mBlurredImage, 0, numBytes);
}
//----------------------------------------------------------------------------
RayTracer::~RayTracer ()
{
delete1(mImage);
delete1(mBlurredImage);
}
//----------------------------------------------------------------------------
void RayTracer::DrawSurface (int numSamples, const Vector3f& lightDirection,
bool blur)
{
float xMult = 2.0f/(mWidth - 1.0f);
float yMult = 2.0f/(mHeight - 1.0f);
float ds = (Far - Near)/(Near*(numSamples - 1.0f));
// Generate a ray per pixel of the image.
for (int j = 0; j < mHeight; ++j)
{
float y = HalfHeight*(-1.0f + yMult*j);
for (int i = 0; i < mWidth; ++i)
{
float x = HalfWidth*(-1.0f + xMult*i);
// The background is zero.
int index = i + mWidth*j;
mImage[index] = 0.0f;
// Compute the ray direction.
Vector3f rayDirection = Near*DVector + x*RVector + y*UVector;
// Compute the ray origin.
float s0 = 1.0f;
Vector3f position0 = Location;
float f0 = mFunction(position0);
// Sample the ray.
for (int k = 0; k < numSamples; ++k)
{
// trace ray E+s*V where 1 <= s <= far/near
float s1 = 1.0f + ds*k;
Vector3f position1 = Location + s1*rayDirection;
float f1 = mFunction(position1);
if (f0*f1 <= 0.0f)
{
// Bisect [s0,s1] to find s for which F(L+s*D) = 0. This
// approach is not accurate near the contour of an object
// since there will be multiple roots that are close
// together and the uniform ray sampling can miss these
// roots. Either Newton's method should be used (or a
// hybrid of bisection and Newton's).
Vector3f surfacePosition, surfaceNormal;
FindSurface(s0, f0, position0, s1, f1, position1,
rayDirection, surfacePosition, surfaceNormal);
// Compute the light intensity.
float dot = lightDirection.Dot(surfaceNormal);
mImage[index] = (dot < 0.0f ? -dot : 0.0f);
break;
}
// Proceed to the next sample interval.
s0 = s1;
position0 = position1;
f0 = f1;
}
}
}
if (blur)
{
BlurImage();
}
}
//----------------------------------------------------------------------------
void RayTracer::FindSurface (float s0, float f0, const Vector3f& position0,
float s1, float f1, const Vector3f& position1,
const Vector3f& rayDirection, Vector3f& surfacePosition,
Vector3f& surfaceNormal)
{
// Check for endpoint zeros.
if (Mathf::FAbs(f0) <= Epsilon)
{
surfacePosition = position0;
surfaceNormal = mGradient(position0);
surfaceNormal.Normalize();
return;
}
if (Mathf::FAbs(f1) <= Epsilon)
{
surfacePosition = position1;
surfaceNormal = mGradient(position1);
surfaceNormal.Normalize();
return;
}
// Bisect the interval [s0,s1].
int i;
for (i = 0; i < MaxBisectSteps; ++i)
{
float s = 0.5f*(s0 + s1);
surfacePosition = Location + s*rayDirection;
float f = mFunction(surfacePosition);
if (Mathf::FAbs(f) <= Epsilon)
{
break;
}
if (f*f0 < 0.0f)
{
s1 = s;
f1 = f;
}
else
{
s0 = s;
f0 = f;
}
}
surfaceNormal = mGradient(surfacePosition);
surfaceNormal.Normalize();
}
//----------------------------------------------------------------------------
void RayTracer::BlurImage ()
{
size_t numBytes = mWidth*mHeight*sizeof(float);
memcpy(mBlurredImage, mImage, numBytes);
for (int y = 1; y < mHeight - 1; ++y)
{
for (int x = 1; x < mWidth - 1; ++x)
{
float value = 0.0f;
for (int dy = -1; dy <= 1; ++dy)
{
for (int dx = -1; dx <= 1; ++dx)
{
value += mImage[(x + dx) + mWidth*(y + dy)];
}
}
mBlurredImage[x + mWidth*y] = value/9.0f;
}
}
memcpy(mImage, mBlurredImage,numBytes);
}
//----------------------------------------------------------------------------
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