forgot to add file in last commit

src/librender/intersection.cpp

@@ -0,0 +1,94 @@
+#include <mitsuba/render/shape.h>
+
+MTS_NAMESPACE_BEGIN
+
+void Intersection::computePartials(const RayDifferential &ray) {
+	Float A[2][2], Bx[2], By[2], x[2];
+	int axes[2];
+
+	/* Compute the texture coordinates partials wrt. 
+	   changes in the screen-space position. Based on PBRT */
+	if (hasUVPartials)
+		return;
+	hasUVPartials = true;
+
+	if (!ray.hasDifferentials) {
+		dudx = dvdx = dudy = dvdy = 0.0f;
+		return;
+	}
+
+	/* Offset of the plane passing through the surface */
+	const Float d = -dot(geoFrame.n, Vector(p));
+
+	const Float txRecip = dot(geoFrame.n, ray.rx.d),
+				tyRecip = dot(geoFrame.n, ray.ry.d);
+
+	if (EXPECT_NOT_TAKEN(txRecip == 0 || tyRecip == 0)) {
+		dudx = dvdx = dudy = dvdy = 0.0f;
+		return;
+	}
+
+	/* Ray distances traveled */
+	const Float tx = -(dot(geoFrame.n, Vector(ray.rx.o)) + d) / 
+		txRecip;
+	const Float ty = -(dot(geoFrame.n, Vector(ray.ry.o)) + d) / 
+		tyRecip;
+
+	/* Calculate the U and V partials by solving two out
+	   of a set of 3 equations in an overconstrained system */
+	Float absX = std::abs(geoFrame.n.x),
+		  absY = std::abs(geoFrame.n.y),
+		  absZ = std::abs(geoFrame.n.z);
+
+	if (absX > absY && absX > absZ) {
+		axes[0] = 1; axes[1] = 2;
+	} else if (absY > absZ) {
+		axes[0] = 0; axes[1] = 2;
+	} else {
+		axes[0] = 0; axes[1] = 1;
+	}
+
+	A[0][0] = dpdu[axes[0]];
+	A[0][1] = dpdv[axes[0]];
+	A[1][0] = dpdu[axes[1]];
+	A[1][1] = dpdv[axes[1]];
+	
+	/* Auxilary intersection point of the adjacent rays */
+	Point px = ray.rx(tx), py = ray.ry(ty);
+	Bx[0] = px[axes[0]] - p[axes[0]];
+	Bx[1] = px[axes[1]] - p[axes[1]];
+	By[0] = py[axes[0]] - p[axes[0]];
+	By[1] = py[axes[1]] - p[axes[1]];
+
+	if (EXPECT_TAKEN(solveLinearSystem2x2(A, Bx, x))) {
+		dudx = x[0]; dvdx = x[1];
+	} else {
+		dudx = 1; dvdx = 0;
+	}
+
+	if (EXPECT_TAKEN(solveLinearSystem2x2(A, By, x))) {
+		dudy = x[0]; dvdy = x[1];
+	} else {
+		dudy = 0; dudy = 1;
+	}
+}
+
+std::string Intersection::toString() const {
+	if (!isValid())
+		return "Intersection[invalid]";
+	std::ostringstream oss;
+	oss << "Intersection[" << std::endl
+		<< "  p = " << p.toString() << "," << std::endl
+		<< "  wi = " << wi.toString() << "," << std::endl
+		<< "  t = " << t << "," << std::endl
+		<< "  geoFrame = " << indent(geoFrame.toString()) << "," << std::endl
+		<< "  shFrame = " << indent(shFrame.toString()) << "," << std::endl
+		<< "  uv = " << uv.toString() << "," << std::endl
+		<< "  dpdu = " << dpdu.toString() << "," << std::endl
+		<< "  dpdv = " << dpdv.toString() << "," << std::endl
+		<< "  shape = " << indent(((Object *)shape)->toString()) << std::endl
+		<< "]";
+	return oss.str();
+}
+
+MTS_NAMESPACE_END