Theme: Radial gradient background and enum for gradient type

This commit replaces the "Use Gradient" checkbox theme option with an
enum and implements a radial background.

Whith this change, it should be easier to implemet other types of more
complex background types, like a world space oriented gradient.

Reviewed By: billreynish, fclem, brecht

Differential Revision: https://developer.blender.org/D6825

2 files changed, 31 insertions, 6 deletions

diff --git a/source/blender/draw/engines/overlay/overlay_background.c b/source/blender/draw/engines/overlay/overlay_background.c
index d98a9066a8e..880f5c49b3e 100644
--- a/source/blender/draw/engines/overlay/overlay_background.c
+++ b/source/blender/draw/engines/overlay/overlay_background.c
@@ -30,6 +30,7 @@
 #define BG_SOLID 0
 #define BG_GRADIENT 1
 #define BG_CHECKER 2
+#define BG_RADIAL 3
 
 void OVERLAY_background_cache_init(OVERLAY_Data *vedata)
 {
@@ -67,11 +68,18 @@ void OVERLAY_background_cache_init(OVERLAY_Data *vedata)
       copy_v3_v3(color_override, v3d->shading.background_color);
       color_override[3] = 1.0f;
     }
-    else if (UI_GetThemeValue(TH_SHOW_BACK_GRAD)) {
-      background_type = BG_GRADIENT;
-    }
     else {
-      background_type = BG_SOLID;
+      switch (UI_GetThemeValue(TH_BACKGROUND_TYPE)) {
+        case TH_BACKGROUND_SINGLE_COLOR:
+          background_type = BG_SOLID;
+          break;
+        case TH_BACKGROUND_GRADIENT_LINEAR:
+          background_type = BG_GRADIENT;
+          break;
+        case TH_BACKGROUND_GRADIENT_RADIAL:
+          background_type = BG_RADIAL;
+          break;
+      }
     }
 
     DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_BACKGROUND;
diff --git a/source/blender/draw/engines/overlay/shaders/background_frag.glsl b/source/blender/draw/engines/overlay/shaders/background_frag.glsl
index 737c3acb438..60fa83e1695 100644
--- a/source/blender/draw/engines/overlay/shaders/background_frag.glsl
+++ b/source/blender/draw/engines/overlay/shaders/background_frag.glsl
@@ -12,6 +12,8 @@ out vec4 fragColor;
 #define BG_SOLID 0
 #define BG_GRADIENT 1
 #define BG_CHECKER 2
+#define BG_RADIAL 3
+#define SQRT2 1.4142135623730950488
 
 /* 4x4 bayer matrix prepared for 8bit UNORM precision error. */
 #define P(x) (((x + 0.5) * (1.0 / 16.0) - 0.5) * (1.0 / 255.0))
@@ -38,6 +40,8 @@ void main()
   float depth = texture(depthBuffer, uvcoordsvar.st).r;
 
   vec3 bg_col;
+  vec3 col_high;
+  vec3 col_low;
 
   switch (bgType) {
     case BG_SOLID:
@@ -45,14 +49,27 @@ void main()
       break;
     case BG_GRADIENT:
       /* XXX do interpolation in a non-linear space to have a better visual result. */
-      vec3 col_high = pow(colorBackground.rgb, vec3(1.0 / 2.2));
-      vec3 col_low = pow(colorBackgroundGradient.rgb, vec3(1.0 / 2.2));
+      col_high = pow(colorBackground.rgb, vec3(1.0 / 2.2));
+      col_low = pow(colorBackgroundGradient.rgb, vec3(1.0 / 2.2));
       bg_col = mix(col_low, col_high, uvcoordsvar.t);
       /* Convert back to linear. */
       bg_col = pow(bg_col, vec3(2.2));
       /*  Dither to hide low precision buffer. (Could be improved) */
       bg_col += dither();
       break;
+    case BG_RADIAL:
+      /* Do interpolation in a non-linear space to have a better visual result. */
+      col_high = pow(colorBackground.rgb, vec3(1.0 / 2.2));
+      col_low = pow(colorBackgroundGradient.rgb, vec3(1.0 / 2.2));
+
+      vec2 uv_n = uvcoordsvar.xy - 0.5;
+      bg_col = mix(col_high, col_low, length(uv_n) * SQRT2);
+
+      /* Convert back to linear. */
+      bg_col = pow(bg_col, vec3(2.2));
+      /*  Dither to hide low precision buffer. (Could be improved) */
+      bg_col += dither();
+      break;
     case BG_CHECKER:
       float size = 8.0 * sizePixel;
       ivec2 p = ivec2(floor(gl_FragCoord.xy / size));