Shading: add Roughness input to Noise and Wave texture nodes

Currently in fractal_noise functions, each subsequent octave doubles the
frequency and reduces the amplitude by half. This patch introduces Roughness
input to Noise and Wave nodes. This multiplier determines how quickly the
amplitudes of the subsequent octaves decrease.

Value of 0.5 will be the default, generating identical noise we had before.
Values above 0.5 will increase influence of each octave resulting in more
"rough" noise, most interesting pattern changes happen there. Values below
0.5 will result in more "smooth" noise.

Differential Revision: https://developer.blender.org/D7065

1 files changed, 28 insertions, 24 deletions

diff --git a/intern/cycles/kernel/svm/svm_fractal_noise.h b/intern/cycles/kernel/svm/svm_fractal_noise.h
index 5b2e4a28fce..57fa8c690ac 100644
--- a/intern/cycles/kernel/svm/svm_fractal_noise.h
+++ b/intern/cycles/kernel/svm/svm_fractal_noise.h
@@ -17,114 +17,118 @@
 CCL_NAMESPACE_BEGIN
 
 /* The fractal_noise_[1-4] functions are all exactly the same except for the input type. */
-ccl_device_noinline float fractal_noise_1d(float p, float octaves)
+ccl_device_noinline float fractal_noise_1d(float p, float octaves, float roughness)
 {
   float fscale = 1.0f;
   float amp = 1.0f;
+  float maxamp = 0.0f;
   float sum = 0.0f;
   octaves = clamp(octaves, 0.0f, 16.0f);
   int n = float_to_int(octaves);
   for (int i = 0; i <= n; i++) {
     float t = noise_1d(fscale * p);
     sum += t * amp;
-    amp *= 0.5f;
+    maxamp += amp;
+    amp *= clamp(roughness, 0.0f, 1.0f);
     fscale *= 2.0f;
   }
   float rmd = octaves - floorf(octaves);
   if (rmd != 0.0f) {
     float t = noise_1d(fscale * p);
     float sum2 = sum + t * amp;
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    sum2 *= ((float)(1 << (n + 1)) / (float)((1 << (n + 2)) - 1));
+    sum /= maxamp;
+    sum2 /= maxamp + amp;
     return (1.0f - rmd) * sum + rmd * sum2;
   }
   else {
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    return sum;
+    return sum / maxamp;
   }
 }
 
 /* The fractal_noise_[1-4] functions are all exactly the same except for the input type. */
-ccl_device_noinline float fractal_noise_2d(float2 p, float octaves)
+ccl_device_noinline float fractal_noise_2d(float2 p, float octaves, float roughness)
 {
   float fscale = 1.0f;
   float amp = 1.0f;
+  float maxamp = 0.0f;
   float sum = 0.0f;
   octaves = clamp(octaves, 0.0f, 16.0f);
   int n = float_to_int(octaves);
   for (int i = 0; i <= n; i++) {
     float t = noise_2d(fscale * p);
     sum += t * amp;
-    amp *= 0.5f;
+    maxamp += amp;
+    amp *= clamp(roughness, 0.0f, 1.0f);
     fscale *= 2.0f;
   }
   float rmd = octaves - floorf(octaves);
   if (rmd != 0.0f) {
     float t = noise_2d(fscale * p);
     float sum2 = sum + t * amp;
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    sum2 *= ((float)(1 << (n + 1)) / (float)((1 << (n + 2)) - 1));
+    sum /= maxamp;
+    sum2 /= maxamp + amp;
     return (1.0f - rmd) * sum + rmd * sum2;
   }
   else {
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    return sum;
+    return sum / maxamp;
   }
 }
 
 /* The fractal_noise_[1-4] functions are all exactly the same except for the input type. */
-ccl_device_noinline float fractal_noise_3d(float3 p, float octaves)
+ccl_device_noinline float fractal_noise_3d(float3 p, float octaves, float roughness)
 {
   float fscale = 1.0f;
   float amp = 1.0f;
+  float maxamp = 0.0f;
   float sum = 0.0f;
   octaves = clamp(octaves, 0.0f, 16.0f);
   int n = float_to_int(octaves);
   for (int i = 0; i <= n; i++) {
     float t = noise_3d(fscale * p);
     sum += t * amp;
-    amp *= 0.5f;
+    maxamp += amp;
+    amp *= clamp(roughness, 0.0f, 1.0f);
     fscale *= 2.0f;
   }
   float rmd = octaves - floorf(octaves);
   if (rmd != 0.0f) {
     float t = noise_3d(fscale * p);
     float sum2 = sum + t * amp;
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    sum2 *= ((float)(1 << (n + 1)) / (float)((1 << (n + 2)) - 1));
+    sum /= maxamp;
+    sum2 /= maxamp + amp;
     return (1.0f - rmd) * sum + rmd * sum2;
   }
   else {
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    return sum;
+    return sum / maxamp;
   }
 }
 
 /* The fractal_noise_[1-4] functions are all exactly the same except for the input type. */
-ccl_device_noinline float fractal_noise_4d(float4 p, float octaves)
+ccl_device_noinline float fractal_noise_4d(float4 p, float octaves, float roughness)
 {
   float fscale = 1.0f;
   float amp = 1.0f;
+  float maxamp = 0.0f;
   float sum = 0.0f;
   octaves = clamp(octaves, 0.0f, 16.0f);
   int n = float_to_int(octaves);
   for (int i = 0; i <= n; i++) {
     float t = noise_4d(fscale * p);
     sum += t * amp;
-    amp *= 0.5f;
+    maxamp += amp;
+    amp *= clamp(roughness, 0.0f, 1.0f);
     fscale *= 2.0f;
   }
   float rmd = octaves - floorf(octaves);
   if (rmd != 0.0f) {
     float t = noise_4d(fscale * p);
     float sum2 = sum + t * amp;
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    sum2 *= ((float)(1 << (n + 1)) / (float)((1 << (n + 2)) - 1));
+    sum /= maxamp;
+    sum2 /= maxamp + amp;
     return (1.0f - rmd) * sum + rmd * sum2;
   }
   else {
-    sum *= ((float)(1 << n) / (float)((1 << (n + 1)) - 1));
-    return sum;
+    return sum / maxamp;
   }
 }