How to convert bump map to normal map?

[Rawalanche]

@jwatte;639173

The manual way of doing this is to use a Sobel filter.
The shader code looks something like:

float height_pu = tex2D(uv + float4(uPixel, 0, 0, 1), theTexture);
float height_mu = tex2D(uv - float4(uPixel, 0, 0, 1), theTexture);
float height_pv = tex2D(uv + float4(0, vPixel, 0, 1), theTexture);
float height_mv = tex2D(uv - float4(0, vPixel, 0, 1), theTexture);
float du = height_mu - height_pu;
float dv = height_mv - height_pv;
float3 N = normalize(float3(du, dv, 1.0/nScale));

uPixel and vPixel is the size of a pixel – 1/1024.0 if you use a 1024x1024 texture.
nScale is a factor for how “strong” the effect is. 1.0 for a 45-degree maximum effect; 10.0 for a fairly strong effect.

Note that uPixel and vPixel do NOT change values at different MIP maps! They should always represent the size of the largest MIP map level.

Sorry, I can’t build a node graph for this right now, but it should be fairly simple to turn this into the obvious texture sample and add/subtract/divide/normalize nodes.

Thank you, this actually seems like something I was looking for. Unfortunately I have no experience with coding, so it’s going to give me hard time converting it to node tree.

I think that this could encourage UE developers to take a step back and look at a bigger picture of making UE4 friendly for new users. Something as trivial as using regular bump map should not be matter of a forum thread with many hit and miss solutions. It should be a no-brainer that doesn’t even require opening manual, let alone participating on a forum.

Right now I am still facing an impossible choice between being able to use texture tiling and take advantage material instancing, but giving up my desired approach of keeping input texture count to minimum, or giving up texture tiling and material instancing to gain ability to generate normal maps out of height maps. That’s kind of decisions I would not like to make.

That being said… I understand this is quite a niche workflow, and may not be worth the time to accommodate for.