# I'm having trouble with the "video scanline" tutorial

I’m currently following this tutorial but because I’m relatively new I can’t follow it. There’s no explanation on how to get the boxes labelled with numbers and I can’t find lerp or x-1. I’m sure this is insanely obvious to anyone who knows what they’re doing, but I kinda clicked on the tutorial because I don’t.

for the lerp you just need to right click the graph and search for lerp. i think the shortcut to it is hold L then click the graph. this will only work in a material.

as for your x-1, well i think you mean 1-x which you again just need to search for by right clicking the graph and searching for “1-”. for this you could also just use a normal subtract node and set pin A to 1.

if theres ever a node you cant find just open the search and start typing its name, if that doesnt work then uncheck context sensitive, and if that doesnt work then your either in the wrong place or you need to be dragging off a reference to something specific.

Thanks for helping me with the 1-x thing I somehow flipped in my head, but I already looked for lerp and it’s all stuff like “lerp_multiplefloat3” and “lerp_scratchgrime2” and while I assume I can use one, I can’t tell which will be usable. I also still have no clue how to get the one labelled with only numbers like in part 4.

the lerp you want is the one that say linearInterpolate in the utility section. its the same one you get by holding L and clicking the graph.

one labelled with only numbers like in part 4

you arent very clear when explaining things. what is part 4 meant to mean? theres many sections to the example so do you mean the fourth section (even though they arent numbered)? theres also many step 4s within the sections. or could you mean the part of the picture of the graph with the comment of 4(theres two of those)? you need to be more descriptive and specific.

i assume that your talking about a “constant 1” as seen in the picture linked below in the section with the comment beginning with a 7. to get a constant just hold a number key and click the graph. so for a constant 1 you would hold the 1 key then click. you can also search for constant in the palette. something similar that could also be used is a scalar parameter which is like a constant in it provides a value but its value can be variable and can be modified from a external source.

https://docs.unrealengine.com/portals/0/images/Engine/Rendering/PostProcessEffects/PostProcessMaterials/PostProcessDemoMaterialOverview/VideoScanlineEffectNetwork.png