How to fill part of layer while all layers recognized?

[Simonsays]

I'm trying to fill a line drawing. I have one layer on top, my line drawing set to multiply. My colour layer below. I would like to fill in colour on the colour layer but need it to recognize all layers while doing that so parts of the line drawing get filled in colour. (Floorplan). Anyone have any ideas on where to check the box so it can do this? Thanks.

[firstdefence]

Welcome to the forum Simon,

Which app are you using?

So the line drawing is a black and white image? 

If you want to fill area's of the floor plan you can use shapes that will sit underneath the line drawing, these shapes can be filled with colours, textures and gradients. You can use any of the ready made shapes or use the pen tool to create curves/paths and apply fills to the custom shape.

 

[Simonsays]

Hi, I'm using affinity photo for colouring comics. I'm looking to block in colour by using the flood fill tool. (paint bucket) Similar to your layer set up but just clicking inside the line art to pop in colour. I know it can be done in photoshop, by using all layers and clicking inside the box (line art like your example) while maintaining your lines drawing. Selecting shapes or masking would simply take way too long. Any ideas? Thanks