Cycles: Implement denoising option for reducing noise in the rendered image

This commit contains the first part of the new Cycles denoising option,
which filters the resulting image using information gathered during rendering
to get rid of noise while preserving visual features as well as possible.

To use the option, enable it in the render layer options. The default settings
fit a wide range of scenes, but the user can tweak individual settings to
control the tradeoff between a noise-free image, image details, and calculation
time.

Note that the denoiser may still change in the future and that some features
are not implemented yet. The most important missing feature is animation
denoising, which uses information from multiple frames at once to produce a
flicker-free and smoother result. These features will be added in the future.

Finally, thanks to all the people who supported this project:

- Google (through the GSoC) and Theory Studios for sponsoring the development
- The authors of the papers I used for implementing the denoiser (more details
  on them will be included in the technical docs)
- The other Cycles devs for feedback on the code, especially Sergey for
  mentoring the GSoC project and Brecht for the code review!
- And of course the users who helped with testing, reported bugs and things
  that could and/or should work better!

1 files changed, 72 insertions, 65 deletions

diff --git a/intern/cycles/util/util_math.h b/intern/cycles/util/util_math.h
index 52b4fa859b7..12abd8e201e 100644
--- a/intern/cycles/util/util_math.h
+++ b/intern/cycles/util/util_math.h
@@ -160,6 +160,78 @@ ccl_device_inline float max4(float a, float b, float c, float d)
 }
 
 #ifndef __KERNEL_OPENCL__
+/* Int/Float conversion */
+
+ccl_device_inline int as_int(uint i)
+{
+	union { uint ui; int i; } u;
+	u.ui = i;
+	return u.i;
+}
+
+ccl_device_inline uint as_uint(int i)
+{
+	union { uint ui; int i; } u;
+	u.i = i;
+	return u.ui;
+}
+
+ccl_device_inline uint as_uint(float f)
+{
+	union { uint i; float f; } u;
+	u.f = f;
+	return u.i;
+}
+
+ccl_device_inline int __float_as_int(float f)
+{
+	union { int i; float f; } u;
+	u.f = f;
+	return u.i;
+}
+
+ccl_device_inline float __int_as_float(int i)
+{
+	union { int i; float f; } u;
+	u.i = i;
+	return u.f;
+}
+
+ccl_device_inline uint __float_as_uint(float f)
+{
+	union { uint i; float f; } u;
+	u.f = f;
+	return u.i;
+}
+
+ccl_device_inline float __uint_as_float(uint i)
+{
+	union { uint i; float f; } u;
+	u.i = i;
+	return u.f;
+}
+#endif /* __KERNEL_OPENCL__ */
+
+/* Versions of functions which are safe for fast math. */
+ccl_device_inline bool isnan_safe(float f)
+{
+	unsigned int x = __float_as_uint(f);
+	return (x << 1) > 0xff000000u;
+}
+
+ccl_device_inline bool isfinite_safe(float f)
+{
+	/* By IEEE 754 rule, 2*Inf equals Inf */
+	unsigned int x = __float_as_uint(f);
+	return (f == f) && (x == 0 || (f != 2.0f*f)) && !((x << 1) > 0xff000000u);
+}
+
+ccl_device_inline float ensure_finite(float v)
+{
+	return isfinite_safe(v)? v : 0.0f;
+}
+
+#ifndef __KERNEL_OPENCL__
 ccl_device_inline int clamp(int a, int mn, int mx)
 {
 	return min(max(a, mn), mx);
@@ -250,57 +322,6 @@ CCL_NAMESPACE_END
 CCL_NAMESPACE_BEGIN
 
 #ifndef __KERNEL_OPENCL__
-/* Int/Float conversion */
-
-ccl_device_inline int as_int(uint i)
-{
-	union { uint ui; int i; } u;
-	u.ui = i;
-	return u.i;
-}
-
-ccl_device_inline uint as_uint(int i)
-{
-	union { uint ui; int i; } u;
-	u.i = i;
-	return u.ui;
-}
-
-ccl_device_inline uint as_uint(float f)
-{
-	union { uint i; float f; } u;
-	u.f = f;
-	return u.i;
-}
-
-ccl_device_inline int __float_as_int(float f)
-{
-	union { int i; float f; } u;
-	u.f = f;
-	return u.i;
-}
-
-ccl_device_inline float __int_as_float(int i)
-{
-	union { int i; float f; } u;
-	u.i = i;
-	return u.f;
-}
-
-ccl_device_inline uint __float_as_uint(float f)
-{
-	union { uint i; float f; } u;
-	u.f = f;
-	return u.i;
-}
-
-ccl_device_inline float __uint_as_float(uint i)
-{
-	union { uint i; float f; } u;
-	u.i = i;
-	return u.f;
-}
-
 /* Interpolation */
 
 template<class A, class B> A lerp(const A& a, const A& b, const B& t)
@@ -318,20 +339,6 @@ ccl_device_inline float triangle_area(const float3& v1,
 }
 #endif  /* __KERNEL_OPENCL__ */
 
-/* Versions of functions which are safe for fast math. */
-ccl_device_inline bool isnan_safe(float f)
-{
-	unsigned int x = __float_as_uint(f);
-	return (x << 1) > 0xff000000u;
-}
-
-ccl_device_inline bool isfinite_safe(float f)
-{
-	/* By IEEE 754 rule, 2*Inf equals Inf */
-	unsigned int x = __float_as_uint(f);
-	return (f == f) && (x == 0 || (f != 2.0f*f)) && !((x << 1) > 0xff000000u);
-}
-
 /* Orthonormal vectors */
 
 ccl_device_inline void make_orthonormals(const float3 N, float3 *a, float3 *b)