Fix #34233: bad alpha blending for 3D texture painting. Same changes as the

previous fix for 2D image painting were done, and also:

* For brushes that do masking (keeping the max contribution to a pixel limited),
  the alpha from textures is now part of the mask. In many cases the logic
  worked out the same and where it didn't it used to cause artifacts.

* Color interpolation for smear and soften tools now happens in premultipied
  space, to avoid bleeding of RGB colors from zero alpha areas.

* Fix a few cases where byte <=> float conversion was not doing the proper
  straight <=> premul conversion.

* Replace some float division by constants with multiplications, is faster.

Note: float texture painting seems to have some issues updating the OpenGL
texture, but issue was already there before this commit.

1 files changed, 10 insertions, 10 deletions

diff --git a/source/blender/blenlib/intern/math_color.c b/source/blender/blenlib/intern/math_color.c
index 3567421daad..cc892795a46 100644
--- a/source/blender/blenlib/intern/math_color.c
+++ b/source/blender/blenlib/intern/math_color.c
@@ -197,9 +197,9 @@ void hex_to_rgb(char *hexcol, float *r, float *g, float *b)
 	if (hexcol[0] == '#') hexcol++;
 
 	if (sscanf(hexcol, "%02x%02x%02x", &ri, &gi, &bi) == 3) {
-		*r = ri / 255.0f;
-		*g = gi / 255.0f;
-		*b = bi / 255.0f;
+		*r = ri * (1.0f / 255.0f);
+		*g = gi * (1.0f / 255.0f);
+		*b = bi * (1.0f / 255.0f);
 		CLAMP(*r, 0.0f, 1.0f);
 		CLAMP(*g, 0.0f, 1.0f);
 		CLAMP(*b, 0.0f, 1.0f);
@@ -394,17 +394,17 @@ void cpack_to_rgb(unsigned int col, float *r, float *g, float *b)
 
 void rgb_uchar_to_float(float col_r[3], const unsigned char col_ub[3])
 {
-	col_r[0] = ((float)col_ub[0]) / 255.0f;
-	col_r[1] = ((float)col_ub[1]) / 255.0f;
-	col_r[2] = ((float)col_ub[2]) / 255.0f;
+	col_r[0] = ((float)col_ub[0]) * (1.0f / 255.0f);
+	col_r[1] = ((float)col_ub[1]) * (1.0f / 255.0f);
+	col_r[2] = ((float)col_ub[2]) * (1.0f / 255.0f);
 }
 
 void rgba_uchar_to_float(float col_r[4], const unsigned char col_ub[4])
 {
-	col_r[0] = ((float)col_ub[0]) / 255.0f;
-	col_r[1] = ((float)col_ub[1]) / 255.0f;
-	col_r[2] = ((float)col_ub[2]) / 255.0f;
-	col_r[3] = ((float)col_ub[3]) / 255.0f;
+	col_r[0] = ((float)col_ub[0]) * (1.0f / 255.0f);
+	col_r[1] = ((float)col_ub[1]) * (1.0f / 255.0f);
+	col_r[2] = ((float)col_ub[2]) * (1.0f / 255.0f);
+	col_r[3] = ((float)col_ub[3]) * (1.0f / 255.0f);
 }
 
 void rgb_float_to_uchar(unsigned char col_r[3], const float col_f[3])