3D noise texture

Dschoonmaker

Is there a built in way to generate a 3D noise texture? If not, how could I do it in GDScript?

TwistedTwigleg

It looks like it is at least possible, since there is a get_noise_3d function (documentation). I have not tried it myself though.

SIsilicon28

You could also try using some shader magic to do it. That's what I did in my Volumetrics Plugin. It comes with a tool to create 3D noise textures almost automatically. You can find the shader somewhere in the scene file here.

Dschoonmaker

@TwistedTwigleg I know how to get noise, but how can I create and fill a 3D texture?

@SIsilicon28 do you mean calculating noise in a shader?

SIsilicon28

@Dschoonmaker That's right.

Dschoonmaker

@SIsilicon28 said: You can find the shader somewhere in the scene file here.

Oh, it's in the scene file. That's why I didn't see it before. I'll look in the .tscn file, although it's probably a good idea to save a .shader file also.

In the function float pnoise(vec3 P, float rep), what is rep?

SIsilicon28

rep stands for repeat. It's how far the texture generates until it repeats itself.

Dschoonmaker

I need to generate noise in the fragment function, how can I convert screen space VERTEX to world space?

SIsilicon28

VERTEX is in view space actually. It's as simple as a matrix multiplication. vec3 world_vert = (CAMERA_MATRIX * vec4(VERTEX, 1.0)).xyz; It has to be converted from a vec3 to a vec4 and back in order for it to be transformed properly.

Dschoonmaker

Oh, I meant view space. Is screen space 2D screen coordinates?

SIsilicon28

Yes, and you get that via SCREEN_UV.

Dschoonmaker

I knew about SCREEN_UV, but I just saw FRAG_COORD and it looks like the same thing. What's the difference?

TwistedTwigleg

I believe that SREEN_UV is the position of the fragement on the screen itself, mapped 0->1, while FRAG_CORD is the position of the fragement in screen space. FRAG_CORD also has a z value for depth, which can be helpful for various effects.

SIsilicon28

Plus, FRAG_COORD's xy range is that of the viewport's pixel size.

Dschoonmaker

Do you know what to do to convert a world space normal to a view space normal, or vice versa? I found the multiplication you used for world space vertex didn't work. Maybe VIEW is useful here?

SIsilicon28

The formula only works on positional vectors. For vectors that represent a direction, replace the 1.0 with 0.0. vec3 normal = (CAMERA_MATRIX * vec4(NORMAL, 0.0)).xyz;

Dschoonmaker

How about the opposite? How could a world space normal be converted to a screen space normal?

SIsilicon28

If by screen space you mean view space, then this should work. vec3 view_normal = (INV_CAMERA_MATRIX * vec4(world_normal, 0.0)).xyz; To do the opposite of a transform, use the inverse of the matrix.

Dschoonmaker

Yes, I meant view space. That makes sense, thanks for your answers!