1
\$\begingroup\$

I am using Unreal Engine 4, and I want to try to procedurally generate a grass texture. For now, I am using a noise block. Now I want to loop through every 16 pixels or whatever (4x4 squares), take the average color of those pixels, and make that all one "pixel". I don't see any for loops, loops, etc. in the pallete though. Can you not do this with the material editor? Thanks.

\$\endgroup\$
  • 1
    \$\begingroup\$ This sounds a bit like mipmapping. Could you read from a deeper mip level to get this kind of local averaging? \$\endgroup\$ – DMGregory May 30 '17 at 18:47
0
\$\begingroup\$

I don't think this can be done through material nodes. However you can use the Custom node to write your own GLSL code, or write a custom GLSL shader.

\$\endgroup\$
  • \$\begingroup\$ You probably meant HLSL \$\endgroup\$ – ColdSteel Sep 30 at 12:23
0
\$\begingroup\$

You can do this but it just makes your nodes messy! It's a bit of a messy approach but I'm not aware of any nodes that gives us quick access to surrounding pixels:

  1. Create const floats ( name them wRatio and hRatio ) and set their values to:
    wRatio : 1.0/texture width
    hRatio: 1.0/texture height

If you want to hit pixel center offset the texture ( or add it to w/hRatio ) by half of wRatio and hRatio.

  1. Create a TexCoord node

  2. Create a BreakOutFloatComponent and attach the TexCoord output to it.

  3. With our new data we now need to Create 9 new (3x3, you can do 16 but do you really want to?) 2d Vectors. The ouput is set by their offset based on the wRatio and hRation. for example {-wRatio,-hRatio} is the top left pixel of the 3x3 setup. Combine the BreakOutFloatComponent with your ratios using add math nodes. Make sure to negate any ratio first by multiplying by -1 using a math multiply node to get the correct coordinate. R output with wRatio and G with hRatio.

  4. Use the append node to combine the new u and v coordinates into a new vector 2d. Repeat this for every offset.

  5. Use each result to sample from the texture as uv input. For this create 9 Texture Sample nodes and connect each offset respectively.

  6. Add all of the color outputs together with the math add node and then divide them by 9 with the math divide node. This is your average color.

Here is the setup for average of 2 lookups average of 2

You can see that this will be a nightmare if you go up in sample count.

Alternatively you can also use a custom expression : https://docs.unrealengine.com/en-us/Engine/Rendering/Materials/ExpressionReference/Custom

Requires you to write some hlsl but the syntax for such function is actually very easy. The blur example points you in the right direction.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.