OutlinePass doesn't work with renderToScreen

Description of the problem

OutlinePass doesn’t work when setting renderToScreen to true. Instead of rendering the outlines, it renders a blank screen.

I have found out through trial and error that OutlinePass requires that it be followed by a ShaderPass (or possibly just another pass) containing something. The postprocessing example uses a ShaderPass with an FXAAShader. Alternatively, a ShaderPass with a CopyShader works too.

I’m not sure if this is a feature or a bug but it was really annoying to try to get it to work.

Three.js version

It happens in the dev version of OutlinePass and the original revision that added it to the repository.

Browser

Tested in Chrome 54.0.2840.99 m (64-bit) and Firefox 50.0

OS

I’m on Windows 7 x64

Hardware Requirements (graphics card, VR Device, …)

I’m using an Intel integrated graphics chipset

[WestLangley]

EffectComposer has not had significant development in 4 years or so. If you are interested in considering alternate implementations, you might want to have a look at @spite’s Wagner API. I expect there would be a lot of interest in revisiting this topic.

[Mugen87]

As far as i know, renderToScreen should always be set to true for the final pass in your chain. If this pass does not evaluate the property, use an additional CopyShader pass for the final render step.

I’m not sure, why some passes don’t check renderToScreen. Besides, some passes (like OutlinePass) are rendering to the readBuffer. Not sure if this approach is correct/consistent. I’ve always thought a pass should basically read its input data from the readBuffer and write its result to the writeBuffer (MaskPass might be an exception). In these cases needsSwap should be set to true so the composer swaps the buffers after the render process.