Concerning tests

Remember even transparent pixels must be drawn. So a transparent background project will still clear every pixel to transparent every frame, which will take up some of the fill rate. This is what the 'clear background' project property is for, so you can turn off that clear in case the background is 100% covered by opaque objects.

Thanks for the info guys.

It makes sense now. As any layer can have a coloured opacity and that would count as a draw, it makes sense that the background layer would as well, in the same way as clearing the background with a transparency would count as a draw.

I suppose I was hoping that flushing the background with 1 colour (or transparency) would be a simpler task for the renderer than rendering an image.

Remember even transparent pixels must be drawn. So a transparent background project will still clear every pixel to transparent every frame, which will take up some of the fill rate. This is what the 'clear background' project property is for, so you can turn off that clear in case the background is 100% covered by opaque objects.

Do transparent layers cause transparent pixels to be drawn as well, or just the objects on them?

Only the transparent pixels of the objects on the layer, unless you've set the layer to be rendered as a texture, in which case I'm not sure if the segment with objects is cropped or if the entire layer is drawn.

Only the transparent pixels of the objects on the layer, unless you've set the layer to be rendered as a texture, in which case I'm not sure if the segment with objects is cropped or if the entire layer is drawn.

Cool, thanks for the info. Where are you getting this? Is there a manual entry on this sort of info?

From forums, articles, conversations with people more knowledgeable than I am, etc. It probably would be good to have a manual entry or maybe a tutorial explaining some of the more technical details behind unsderstanding rendering.