Rendering order of Render Layers?

My Blending Life portrait is pretty complex, with a lot of elements that take a long time to render and some that don’t. So I’ve placed most of the parts on separate layers and made a number of Render Layers that I can render separately in the Compositor and see the results much sooner that if I had to render the entire file each time.

But it’s also leading to some oddness when I render the full file (F12). For example, I have the hair particle meshes on a separate layer, and they are also on a separate Render Layer, and on the Render Layer with the main body mesh. The Composite Output node does not have the Render Layer with just the hair meshes in its pipeline, only that with both body & hair.

But when rendering with F12 and the Do Composite button enabled, the Render Layers appear in each part in this order: Ring, Boxer (including hair meshes and sweat layer), and then also the Hair Meshes solo layer for some reason, and unfortunately, because this is the last Render Layer to render, everything else that was visible from the other Render Layers is covered up, so to speak. Only the hair particles are visible when the rendering moves on to another part.

I’m confident that once the rendering is totally done, the Compositor will sort it all out and assemble the image I expect, but I also like to check the image as it progresses, so if there’s anything really wrong I can abort, fix it and start again. But that last Render Layer of hair alone makes this not happen.

Is there some way to prevent a Render layer from rendering short of disabling the layers that are included in it? I need those layers enabled for the combo body/hair Render Layer, but don’t want the separate hair-only Render layer in the rendering sequence, or at least, I’d like to make it not render last, when it covers everything else up.

The best thing I can tell you is to assign each renderlayer to a separate scene, then if you don’t want it to render you can just change the scene on that render layer to an already rendered render layer. I believe scenes render in the order in which they are created but I can’t swear to it. Any changed scene may composite twice but it’ll only render once, unless you disconnect it from the composite and have the “Free Unused” option enabled. An added benefit is that if you jump to a specific scene and render it you can come back to the current scene and recomposite withoput penalty of having saved buffers from other scenes cleared which is as major pain in the render-time ass (really only usefull when using FSA). Noobs won’t care about that last part but I know you do.

I always render from an empty scene (camera only with “Key” enabled) and use that as a compositor only scene without it’s default render layer in the composition. You get a slight slow down as this scene is rendered anyway but it makes controlling the flow much easier and less confusing.