Armature: Add back Stick bone draw type.

The actual code is a bit convoluted but allows good and "pseudo efficient"
drawing. (pseudo efficient because rendering instances with that amount of
vertices is really inneficient. We should go full procedural but need to
have bufferTexture implemented first) But drawing speed is not a bottleneck
here and it's already a million time less crappy than the old (2.79) immediate
mode method.

Instead of drawing actual wires with different width we render a triangle
fan batch (containing 3 fans: bone, head, tail) which is then oriented in
screen space to the bone direction. We then interpolate a float value
accross vertices giving us a nice blend factor to blend the colors and
gives us really smooth interpolation inside the bone.

The outside edge still being geometry will be antialiased by MSAA if enabled.

1 files changed, 77 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_cache.c b/source/blender/draw/intern/draw_cache.c
index 1a4a9be00bd..2366fa556b9 100644
--- a/source/blender/draw/intern/draw_cache.c
+++ b/source/blender/draw/intern/draw_cache.c
@@ -88,6 +88,7 @@ static struct DRWShapeCache {
 	Gwn_Batch *drw_bone_envelope_outline;
 	Gwn_Batch *drw_bone_point;
 	Gwn_Batch *drw_bone_point_wire;
+	Gwn_Batch *drw_bone_stick;
 	Gwn_Batch *drw_bone_arrows;
 	Gwn_Batch *drw_camera;
 	Gwn_Batch *drw_camera_frame;
@@ -2104,6 +2105,82 @@ Gwn_Batch *DRW_cache_bone_point_wire_outline_get(void)
 	return SHC.drw_bone_point_wire;
 }
 
+/* keep in sync with armature_stick_vert.glsl */
+#define COL_WIRE (1 << 0)
+#define COL_HEAD (1 << 1)
+#define COL_TAIL (1 << 2)
+#define COL_BONE (1 << 3)
+
+#define POS_HEAD (1 << 4)
+#define POS_TAIL (1 << 5)
+#define POS_BONE (1 << 6)
+
+Gwn_Batch *DRW_cache_bone_stick_get(void)
+{
+	if (!SHC.drw_bone_stick) {
+#define CIRCLE_RESOL 12
+		unsigned int v = 0;
+		unsigned int flag;
+		const float radius = 2.0f; /* head/tail radius */
+		float pos[2];
+
+		/* Position Only 2D format */
+		static Gwn_VertFormat format = { 0 };
+		static struct { uint pos, flag; } attr_id;
+		if (format.attrib_ct == 0) {
+			attr_id.pos  = GWN_vertformat_attr_add(&format, "pos",  GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+			attr_id.flag = GWN_vertformat_attr_add(&format, "flag", GWN_COMP_U32, 1, GWN_FETCH_INT);
+		}
+
+		const unsigned int vcount = (CIRCLE_RESOL + 1) * 2 + 6;
+
+		Gwn_VertBuf *vbo = GWN_vertbuf_create_with_format(&format);
+		GWN_vertbuf_data_alloc(vbo, vcount);
+
+		Gwn_IndexBufBuilder elb;
+		GWN_indexbuf_init_ex(&elb, GWN_PRIM_TRI_FAN, (CIRCLE_RESOL + 2) * 2 + 6 + 2, vcount, true);
+
+		/* head/tail points */
+		for (int i = 0; i < 2; ++i) {
+			/* center vertex */
+			copy_v2_fl(pos, 0.0f);
+			flag  = (i == 0) ? POS_HEAD : POS_TAIL;
+			flag |= (i == 0) ? COL_HEAD : COL_TAIL;
+			GWN_vertbuf_attr_set(vbo, attr_id.pos,  v, pos);
+			GWN_vertbuf_attr_set(vbo, attr_id.flag, v, &flag);
+			GWN_indexbuf_add_generic_vert(&elb, v++);
+			/* circle vertices */
+			flag |= COL_WIRE;
+			for (int a = 0; a < CIRCLE_RESOL; a++) {
+				pos[0] = radius * sinf((2.0f * M_PI * a) / ((float)CIRCLE_RESOL));
+				pos[1] = radius * cosf((2.0f * M_PI * a) / ((float)CIRCLE_RESOL));
+				GWN_vertbuf_attr_set(vbo, attr_id.pos,  v, pos);
+				GWN_vertbuf_attr_set(vbo, attr_id.flag, v, &flag);
+				GWN_indexbuf_add_generic_vert(&elb, v++);
+			}
+			/* Close the circle */
+			GWN_indexbuf_add_generic_vert(&elb, v - CIRCLE_RESOL);
+
+			GWN_indexbuf_add_primitive_restart(&elb);
+		}
+
+		/* Bone rectangle */
+		pos[0] = 0.0f;
+		for (int i = 0; i < 6; ++i) {
+			pos[1] = (i == 0 || i == 3) ? 0.0f : ((i < 3) ? 1.0f : -1.0f);
+			flag   = ((i <  2 || i >  4) ? POS_HEAD : POS_TAIL) |
+			         ((i == 0 || i == 3) ? 0 : COL_WIRE) | COL_BONE | POS_BONE;
+			GWN_vertbuf_attr_set(vbo, attr_id.pos,  v, pos);
+			GWN_vertbuf_attr_set(vbo, attr_id.flag, v, &flag);
+			GWN_indexbuf_add_generic_vert(&elb, v++);
+		}
+
+		SHC.drw_bone_stick = GWN_batch_create_ex(GWN_PRIM_TRI_FAN, vbo, GWN_indexbuf_build(&elb), GWN_BATCH_OWNS_VBO);
+#undef CIRCLE_RESOL
+	}
+	return SHC.drw_bone_stick;
+}
+
 static void set_bone_axis_vert(
         Gwn_VertBuf *vbo, uint axis, uint pos, uint col,
         unsigned int *v, const float *a, const float *p, const float *c)