Implement a new dedicated weight painting shader.

Move the weight paint drawing to the fragment shader. The shader
uses a texture that uses the U.coba_weight custom color band, or
an internal color band.

In addition to actual weights, the shader has to display two
alert colors: missing vertex group, and zero weight. The zero
weight alert has to be blended with regular weight colors,
so that a single alert vertex surrounded by weighted ones is
still visible.

Reviewers: campbellbarton, fclem

Differential Revision: https://developer.blender.org/D3675

1 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/draw/modes/shaders/paint_weight_vert.glsl b/source/blender/draw/modes/shaders/paint_weight_vert.glsl
new file mode 100644
index 00000000000..78a3695c82c
--- /dev/null
+++ b/source/blender/draw/modes/shaders/paint_weight_vert.glsl
@@ -0,0 +1,15 @@
+
+uniform mat4 ModelViewProjectionMatrix;
+
+in float weight;
+in vec3 pos;
+
+out vec2 weight_interp; /* (weight, alert) */
+
+void main()
+{
+	gl_Position = ModelViewProjectionMatrix * vec4(pos, 1.0);
+
+	/* Separate actual weight and alerts for independent interpolation */
+	weight_interp = max(vec2(weight, -weight), 0.0);
+}