Fix T67939: GPencil Noise modifier wrong random calculation

There were several problems in the old random calculation:

* Different result in the viewport and render.
* Noise "pop" in some frames. 
* Random number was calculated every time the file was opened, so get different results.

Now, instead to calculate the random numbers when n number of frames changed, the random values are calculated using a unique seed by stroke.

Also, a new Seed parameter has been added and this adds more control in the noise generated. This value can be animated and get more variations.

Differential Revision: http://developer.blender.org/D5393

1 files changed, 2 insertions, 8 deletions

diff --git a/source/blender/makesdna/DNA_gpencil_modifier_types.h b/source/blender/makesdna/DNA_gpencil_modifier_types.h
index c2a9d3cf296..47347753f42 100644
--- a/source/blender/makesdna/DNA_gpencil_modifier_types.h
+++ b/source/blender/makesdna/DNA_gpencil_modifier_types.h
@@ -90,16 +90,10 @@ typedef struct NoiseGpencilModifierData {
   float factor;
   /** How many frames before recalculate randoms. */
   int step;
-  /** Last gp frame used. */
-  int gp_frame;
-  /** First scene frame used. */
-  int scene_frame;
-  /** Random values. */
-  float vrand1, vrand2;
-  struct RNG *rng;
   /** Custom index for passes. */
   int layer_pass;
-  char _pad[4];
+  /** Random seed */
+  int seed;
 } NoiseGpencilModifierData;
 
 typedef enum eNoiseGpencil_Flag {