Unreal Engine Textures – Oded Maoz Erell's CG Log

UE4 – Triplanar projection mapping setup

Posted on November 2, 2020November 4, 2020 by Oded Maoz Erell

Software:
Unreal Engine 4.25

Triplanar Projection Mapping can be an effective texture mapping solution for cases where the model doesn’t have naturally flowing continuous UV coordinates, or there is a need to have the texture projected independently of UV channels, with minimally visible stretching and other mapping artifacts.
Classic use cases for Triplanar Projection Mapping are terrains and organic materials. provided that the image being used is a seamless texture, no seams will be visible because this projection type isn’t affected by UV coordinates.
Triplanar Projection Mapping can also be used in world space to create a continuous texture between separate meshes, allowing the meshes to be indestructibly transformed and edited.

How does Triplanar Projection Mapping work?
Triplanar Projection Mapping is a linear blend between 3 orthogonal 2D planar texture projections, typically each aligned to a natural world or object axis.
The more the surface faces an axis, the higher the weight of this axis projection in the final blend.

UE4 local (object) space Triplanar Projection Mapping material setup:
* It’s usually more efficient to create this setup as a Material Function

Local shading coordinates are multiplied by by a “density” parameter to allow convenient scaling of the projected.
The scaled coordinates vector is separated to its components who are combined to 3 pairs of planar coordinates XY, XZ and YZ, and fed as the sample coordinates to the 3 Texture Sample nodes.
The Vertex Normal input vector is transformed to local space, converted to absolute value (absolute orientation in the positive axes octant) and separated to its X, Y and Z components so they can serve as blend weights in the mix.
Each of the 3 planar axis projections is multiplied by the blend factors, and the resulting values are added to the raw mix.
A value of 1.0 is divided by the Normal vector component values to obtain the factor needed to normalize the blend result to a value of 1.0.
The raw blend value is multiplied by the normalizing factor so the blend resulting color will be normalized.
* The blend weights should add to a value of 1.0, but a unit vector’s values add up to more than 1 in diagonal directions. for this reason, without this final step, the color of the texture in point on the surface that are diagonal to the projection axes will appear brighter than in points on the surface that face a projection axis.

An example of Triplanar Projection Mapping in world space:

A bunch of Blender monkeys (Suzanne) continuously textured using world space Triplanar Projection Mapping:

UE4 – Procedural 3D noise bump setups

Posted on October 31, 2020November 2, 2020 by Oded Maoz Erell

Software:
Unreal Engine 4.25

Yet another case where I develop my own costly solution only to find out afterwards that there’s actually a much more efficient built-in solution.. 😀

In this case the subject is deriving a bump normal from a procedural or non-uv projected height map/texture (like noise, or tri-planar mapping for example).

The built-in way:
Using the pre-made material functions, PreparePerturbNormalHQ and PerturbNormalHQ, the first of which uses the low level Direct3D functions DDX and DDY to derive the two extra surface adjacent values needed to derive a bump normal, and the last uses the 3 values to generate a world-space bump normal:

Noise coordinates are obtained by multiplying the surface shading point local position by a value to set the pattern density.
The Noise output value is multiplied by a factor to set the resulting bump intensity.
The PreparePerturbNormalHQ function is used to derive the 2 extra values needed to derive a bump normal.
The PerturbNormalHQ function is used to derive the World-Space bump normal.
Note:
Using this method, the material’s normal input must be set to world-space by unchecking Tangent Space Normal in the material properties.

The method I’m using:
This method is significantly more expensive in the number of shader instructions, but in my opinion, generates a better quality bump.
Sampling 3 Noise nodes at 3 adjacent locations in tangent-space to derive the 3 input values necessary for the NormalFromFunction material function:

Noise coordinates are obtained by multiplying the surface shading point local position by a value to set the pattern density.
Crossing the vertex normal with the vertex tangent vectors to derive the bitangent (sometimes called “binormal”).
Multiplying the vertex-tangent and bitangent vectors by a bump-offset* factor to create the increment steps to the additional sampled Noise values.
* This factor should be parameter for easy tuning, since it determines the distance between the height samples in tangent space.
The increment vectors are added to the local-position to get the final height samples positions.
The NormalFromFunction material function is used to derive a tangent-space normal from the 3 supplied height samples.

Note:
From my experience, even though the UV1, UV2 and UV3 inputs of the NormalFromFunction are annotated as V3, the function will only work is the inputs are a scalar value and not a vector/color.

UE4 – Quick fix for normal map encoding

Posted on July 6, 2020October 31, 2020 by Oded Maoz Erell

Software:
Unreal Engine 4.25 | Photoshop 2020

Quick UE normal map tip:
If you load a normal map into a UE material and the result appears inverted, i.e. holes instead of bumps or the other way:

The quick fix:

In the texture settings, check the Flip Green Channel option and save it:

The deep fix:
* This can be performed an automated action on multiple files

Open the normal map in Photoshop
In the Channels panel, select the Green channel
Press Ctrl + I,
Or Select Image > Adjustments > Invert
To invert the green channel.
Save the texture and reload into Unreal Engine.

Inverted normal map:

Fixed normal map: