I'm trying to mix two textures for a large environment scene. The base texture is a JPEG (opaque), seamless and tiled. The second texture is a PNG with transparency (using it to give variety to the background hills). I've mixed the PNG over the tiled JPEG texture using the PNG alpha as the factor.. but the rendered result has problems (when I add a black background layer in photoshop it appears correctly)
EDIT: This node setup is actually correct... problem arose from having a second incorrect material on the same surface.