Fix for wrong behavior of 'darken' blend mode with factor.

The formula was not consistent across Blender and behaved strangely, now it is
a simple linear blend between color1 and min(color1, color2).

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D489

2 files changed, 2 insertions, 2 deletions

diff --git a/intern/cycles/kernel/shaders/node_mix.osl b/intern/cycles/kernel/shaders/node_mix.osl
index c2c397c6446..dd54fd814de 100644
--- a/intern/cycles/kernel/shaders/node_mix.osl
+++ b/intern/cycles/kernel/shaders/node_mix.osl
@@ -88,7 +88,7 @@ color node_mix_diff(float t, color col1, color col2)
 
 color node_mix_dark(float t, color col1, color col2)
 {
-	return min(col1, col2 * t);
+	return min(col1, col2) * t + col1 * (1.0 - t);
 }
 
 color node_mix_light(float t, color col1, color col2)
diff --git a/intern/cycles/kernel/svm/svm_mix.h b/intern/cycles/kernel/svm/svm_mix.h
index 4e834b7c500..015925ab01e 100644
--- a/intern/cycles/kernel/svm/svm_mix.h
+++ b/intern/cycles/kernel/svm/svm_mix.h
@@ -89,7 +89,7 @@ ccl_device float3 svm_mix_diff(float t, float3 col1, float3 col2)
 
 ccl_device float3 svm_mix_dark(float t, float3 col1, float3 col2)
 {
-	return min(col1, col2*t);
+	return min(col1, col2)*t + col1*(1.0 - t);
 }
 
 ccl_device float3 svm_mix_light(float t, float3 col1, float3 col2)