Scene Breakdown

Note: Please see "Crash Dump Files" as well.

This part is a bit more work, but sometimes you have scene that simply do not wont to render.

You can change thousands of settings in a full scene with hundrets of objects, shaders, lights, textures, plugins.

I have personally seen it very often, a lot of artists are trying to find an issue inside a production scene and change one value, render, then that other value, render,...

But do you have time to change everything one by one?
Often the issue is caused by one single object.
So how long until you find this needle in a haystack?

So the idea of the scene breakdown is to reduce the possibilites. And do that very fast.

The workflow is to change something (save the scene with a meaningful name what you have changed) and submit it to the farm.

While the scene is on the farm, you can probably do the next test scene and also submit it.

You could end up with 10 scenes at the same time rendering on the farm to see which one works.

Global changes

First step in all cases: Fast Antialiasing

Set the Antialiasing to a low setting (Fix samples -2 -2 and no adaptive AA)
and/or reduce the image resolution.

Reduce area light samples.

Make a small test scene first.
Is it the geometry?

Is it a light?

Is the scene itself corrupt?/Is it a render setting?

Remove all Objects and place an (animated) sphere/cube into the scene.

Same for the lights, remove all lights and create a directional light only.

If it renders, you know it is some object.

If not, either the render settings, the render app/renderer in general or the scene file itself.
Create a brand new scene with a cube only.
If it renders, it is not the render app.

Perhaps the scene file itself is corrupt?
Try to create a new scene and merge your old into that one.

Make the test render fast and test if it is one of these render features.

Disable displacement in your render settings.

Disable shadows.

Disable volume rendering.

Disable motion blur.

Remove all textures or replace all texture connections with a single 256x256 pixel image.

Is it a shader?

Remove all shaders and textures from the scene.
Apply a simple shader like lambert to all objects.

If you know that it is one of the shader network nodes,

then test single features of the shading network.

Create multiple scenes with only single parts of the shading network.

You have two ways:

Either remove parts of the shading network one by one and send them to render:

-first: no displacement

-then: no bump mapping

-then: no reflection

...

exclusively test single parts of the shading network:

- Main shader only (no textures)

- Main shader + Displacement

- Main shader + Diffuse texture

- Main shader + Reflection

- Main shader + Ambient Occlusion

- Main shader + Bump mapping

...

Per Object

Is it one of my objects?

Which one?

Remove half of your objects.
Save it as "_halfA".
Open the orginal scene, remove the other half and save it as "_halfB".

If one of these scenes render and the other not, then is is an object in one half.

Repeat the half-splitting ("_halfAA"+"_halfAB", "_halfABA"+"_halfABB"...) until you have the object.

Note: it could be the geometry, the shader or a texture applied to this object.