diff options
Diffstat (limited to 'intern/cycles/kernel/kernel_montecarlo.h')
| -rw-r--r-- | intern/cycles/kernel/kernel_montecarlo.h | 31 |
1 files changed, 21 insertions, 10 deletions
diff --git a/intern/cycles/kernel/kernel_montecarlo.h b/intern/cycles/kernel/kernel_montecarlo.h index a933be970c2..acd5086be3a 100644 --- a/intern/cycles/kernel/kernel_montecarlo.h +++ b/intern/cycles/kernel/kernel_montecarlo.h @@ -199,21 +199,27 @@ ccl_device float3 ensure_valid_reflection(float3 Ng, float3 I, float3 N) float NdotNg = dot(N, Ng); float3 X = normalize(N - NdotNg * Ng); + /* Keep math expressions. */ + /* clang-format off */ /* Calculate N.z and N.x in the local coordinate system. * * The goal of this computation is to find a N' that is rotated towards Ng just enough * to lift R' above the threshold (here called t), therefore dot(R', Ng) = t. * - * According to the standard reflection equation, this means that we want dot(2*dot(N', I)*N' - I, Ng) = t. + * According to the standard reflection equation, + * this means that we want dot(2*dot(N', I)*N' - I, Ng) = t. * - * Since the Z axis of our local coordinate system is Ng, dot(x, Ng) is just x.z, so we get 2*dot(N', I)*N'.z - I.z = t. + * Since the Z axis of our local coordinate system is Ng, dot(x, Ng) is just x.z, so we get + * 2*dot(N', I)*N'.z - I.z = t. * - * The rotation is simple to express in the coordinate system we formed - since N lies in the X-Z-plane, we know that - * N' will also lie in the X-Z-plane, so N'.y = 0 and therefore dot(N', I) = N'.x*I.x + N'.z*I.z . + * The rotation is simple to express in the coordinate system we formed - + * since N lies in the X-Z-plane, we know that N' will also lie in the X-Z-plane, + * so N'.y = 0 and therefore dot(N', I) = N'.x*I.x + N'.z*I.z . * * Furthermore, we want N' to be normalized, so N'.x = sqrt(1 - N'.z^2). * - * With these simplifications, we get the final equation 2*(sqrt(1 - N'.z^2)*I.x + N'.z*I.z)*N'.z - I.z = t. + * With these simplifications, + * we get the final equation 2*(sqrt(1 - N'.z^2)*I.x + N'.z*I.z)*N'.z - I.z = t. * * The only unknown here is N'.z, so we can solve for that. * @@ -227,8 +233,11 @@ ccl_device float3 ensure_valid_reflection(float3 Ng, float3 I, float3 N) * c = I.z*t + a * N'.z = +-sqrt(0.5*(+-b + c)/a) * - * Two solutions can immediately be discarded because they're negative so N' would lie in the lower hemisphere. + * Two solutions can immediately be discarded because they're negative so N' would lie in the + * lower hemisphere. */ + /* clang-format on */ + float Ix = dot(I, X), Iz = dot(I, Ng); float Ix2 = sqr(Ix), Iz2 = sqr(Iz); float a = Ix2 + Iz2; @@ -237,8 +246,9 @@ ccl_device float3 ensure_valid_reflection(float3 Ng, float3 I, float3 N) float c = Iz * threshold + a; /* Evaluate both solutions. - * In many cases one can be immediately discarded (if N'.z would be imaginary or larger than one), so check for that first. - * If no option is viable (might happen in extreme cases like N being in the wrong hemisphere), give up and return Ng. */ + * In many cases one can be immediately discarded (if N'.z would be imaginary or larger than + * one), so check for that first. If no option is viable (might happen in extreme cases like N + * being in the wrong hemisphere), give up and return Ng. */ float fac = 0.5f / a; float N1_z2 = fac * (b + c), N2_z2 = fac * (-b + c); bool valid1 = (N1_z2 > 1e-5f) && (N1_z2 <= (1.0f + 1e-5f)); @@ -256,8 +266,9 @@ ccl_device float3 ensure_valid_reflection(float3 Ng, float3 I, float3 N) valid1 = (R1 >= 1e-5f); valid2 = (R2 >= 1e-5f); if (valid1 && valid2) { - /* If both solutions are valid, return the one with the shallower reflection since it will be closer to the input - * (if the original reflection wasn't shallow, we would not be in this part of the function). */ + /* If both solutions are valid, return the one with the shallower reflection since it will be + * closer to the input (if the original reflection wasn't shallow, we would not be in this + * part of the function). */ N_new = (R1 < R2) ? N1 : N2; } else { |