DRW: Implement Hair Weight drawing

Fixes T57931 Particle weight edit mode is not supported.

There is a bug that prevent refresh of the toolsettings on which is based
the weight / non-weight display selection (see T58086).

1 files changed, 42 insertions, 0 deletions

diff --git a/source/blender/draw/modes/shaders/particle_strand_vert.glsl b/source/blender/draw/modes/shaders/particle_strand_vert.glsl
index 077d6a64f9b..9db62a581cb 100644
--- a/source/blender/draw/modes/shaders/particle_strand_vert.glsl
+++ b/source/blender/draw/modes/shaders/particle_strand_vert.glsl
@@ -9,11 +9,53 @@ out vec4 finalColor;
 out vec2 radii;
 #endif
 
+vec3 weight_to_rgb(float weight)
+{
+	vec3 r_rgb;
+	float blend = ((weight / 2.0) + 0.5);
+
+	if (weight <= 0.25) {    /* blue->cyan */
+		r_rgb[0] = 0.0;
+		r_rgb[1] = blend * weight * 4.0;
+		r_rgb[2] = blend;
+	}
+	else if (weight <= 0.50) {  /* cyan->green */
+		r_rgb[0] = 0.0;
+		r_rgb[1] = blend;
+		r_rgb[2] = blend * (1.0 - ((weight - 0.25) * 4.0));
+	}
+	else if (weight <= 0.75) {  /* green->yellow */
+		r_rgb[0] = blend * ((weight - 0.50) * 4.0);
+		r_rgb[1] = blend;
+		r_rgb[2] = 0.0;
+	}
+	else if (weight <= 1.0) {  /* yellow->red */
+		r_rgb[0] = blend;
+		r_rgb[1] = blend * (1.0 - ((weight - 0.75) * 4.0));
+		r_rgb[2] = 0.0;
+	}
+	else {
+		/* exceptional value, unclamped or nan,
+		 * avoid uninitialized memory use */
+		r_rgb[0] = 1.0;
+		r_rgb[1] = 0.0;
+		r_rgb[2] = 1.0;
+	}
+
+	return r_rgb;
+}
+
+#define DECOMPRESS_RANGE 1.0039
+
 void main()
 {
 	gl_Position = ModelViewProjectionMatrix * vec4(pos, 1.0);
 
+#ifdef USE_WEIGHT
+	finalColor = vec4(weight_to_rgb(color * DECOMPRESS_RANGE), 1.0);
+#else
 	finalColor = mix(colorWire, colorEdgeSelect, color);
+#endif
 
 #ifdef USE_POINTS
 	gl_PointSize = sizeVertex;