[libgdx] Fixed mixing unweighted meshes that aren't keyed on frame zero.

closes #925

spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/Animation.java

@@ -862,6 +862,8 @@ public class Animation {
 
 	/** Changes a slot's {@link Slot#getAttachmentVertices()} to deform a {@link VertexAttachment}. */
 	static public class DeformTimeline extends CurveTimeline {
+		static private float[] zeros = new float[64];
+
 		int slotIndex;
 		VertexAttachment attachment;
 		private final float[] frames; // time, ...
@@ -923,20 +925,43 @@ public class Animation {
 			FloatArray verticesArray = slot.getAttachmentVertices();
 			float[][] frameVertices = this.frameVertices;
 			int vertexCount = frameVertices[0].length;
-			if (verticesArray.size != vertexCount && pose != setup) alpha = 1; // Don't mix from uninitialized slot vertices.
 			float[] vertices = verticesArray.setSize(vertexCount);
 
 			float[] frames = this.frames;
 			if (time < frames[0]) { // Time is before first frame.
+				VertexAttachment vertexAttachment = (VertexAttachment)slotAttachment;
+
 				switch (pose) {
 				case setup:
-					verticesArray.size = 0;
-					return;
+					break;
 				case current:
-					alpha = 1 - alpha;
-					for (int i = 0; i < vertexCount; i++)
-						vertices[i] *= alpha;
+					if (alpha == 1) break;
+					if (vertexAttachment.getBones() == null) {
+						// Unweighted vertex positions.
+						float[] setupVertices = vertexAttachment.getVertices();
+						for (int i = 0; i < vertexCount; i++)
+							vertices[i] += (setupVertices[i] - vertices[i]) * alpha;
+					} else {
+						// Weighted deform offsets.
+						alpha = 1 - alpha;
+						for (int i = 0; i < vertexCount; i++)
+							vertices[i] *= alpha;
+					}
+					// Fall thru.
+				default:
+					return;
+				}
+
+				float[] zeroVertices;
+				if (vertexAttachment.getBones() == null) {
+					// Unweighted vertex positions (setup pose).
+					zeroVertices = vertexAttachment.getVertices();
+				} else {
+					// Weighted deform offsets (zeros).
+					zeroVertices = zeros;
+					if (zeroVertices.length < vertexCount) zeros = zeroVertices = new float[vertexCount];
 				}
+				System.arraycopy(zeroVertices, 0, vertices, 0, vertexCount);
 				return;
 			}