Cloud shader problems

[Seiko4169]

Hi,
I'm trying to translate a cloud shader from shader toy to GML and as a relative newbie to shaders I'm struggling.

The original is here...

Spoiler: Fast clouds

https://www.shadertoy.com/view/XsjSRt

My code so far is resulting in the sprite simply flickering from the sky blue to slight variations of the sky blue.

Spoiler: Shader code

//
// Simple passthrough fragment shader
//
varying vec2   v_vPosition;
varying vec2      v_vTexcoord;
varying vec4      v_vColour;
uniform float     time;                  // Time
uniform sampler2D noiseChannel;             // Noise Texture

const float timeScale = 10.0;
const float cloudScale = 0.5;
const float skyCover = 0.6;
const float softness = 0.2;
const float brightness = 0.0;
const int noiseOctaves = 8;
const float curlStrain = 3.0;

float saturate(float num)
{
    return clamp(num,0.0,1.0);
}

float noise(vec2 uv)
{
   return texture2D(noiseChannel,uv).r;
}

vec2 rotate(vec2 uv)
{
    uv = uv + noise(uv*0.2)*0.005;
    float rot = curlStrain;
    float sinRot=sin(rot);
    float cosRot=cos(rot);
    mat2 rotMat = mat2(cosRot,-sinRot,sinRot,cosRot);
    return uv * rotMat;
}

float fbm (vec2 uv)
{
    float rot = 1.57;
    float sinRot=sin(rot);
    float cosRot=cos(rot);
    float f = 0.0;
    float total = 0.0;
    float mul = 0.5;
    mat2 rotMat = mat2(cosRot,-sinRot,sinRot,cosRot);
  
    for(int i = 0;i < noiseOctaves;i++)
    {
        f += noise(uv+time*0.00015*timeScale*(1.0-mul))*mul;
        total += mul;
        uv *= 3.0;
        uv=rotate(uv);
        mul *= 0.5;
    }
    return f/total;
}

void main(void)
{
 
    vec2 uv = v_vPosition.xy/(40000.0*cloudScale);
    float cover = 0.9;
    float bright = brightness*(1.8-cover);
  
    float color1 = fbm(uv-0.5+time*0.00004*timeScale);
    float color2 = fbm(uv-10.5+time*0.00002*timeScale);
  
    float clouds1 = smoothstep(1.0-cover,min((1.0-cover)+softness*2.0,1.0),color1);
    float clouds2 = smoothstep(1.0-cover,min((1.0-cover)+softness,1.0),color2);
  
    float cloudsFormComb = saturate(clouds1+clouds2);
  
    vec4 skyCol = vec4(0.6,0.8,1.0,1.0);
    float cloudCol = saturate(saturate(1.0-pow(color1,1.0)*0.2)*bright);
    vec4 clouds1Color = vec4(cloudCol,cloudCol,cloudCol,1.0);
    vec4 clouds2Color = mix(clouds1Color,skyCol,0.25);
    vec4 cloudColComb = mix(clouds1Color,clouds2Color,saturate(clouds2-clouds1));
  
    gl_FragColor = mix(skyCol,cloudColComb,cloudsFormComb);
}

I have set the texture to a noise texture (128x128) separate texture page (the same as the channel0 texture on Shadertoy) but simply don't get to see any clouds.

Having spent the last 5 hours reading tutorials and looking at other samples I still don't know why I'm getting the results I'm getting and would really appreciate some guidance.

 

[flyingsaucerinvasion]

Make sure you set the texture to repeat.

You'll probably want to revert the "brightness" constant back to 1.0, instead of leaving it at 0.0.

Make sure you've passed in v_vPosition correctly from the vertex shader. It should be equal to in_Position.xy.

Since you're only using one texture here, you might as well make the noise texture the base texture.

 

[Seiko4169]

Thanks yes I set the noise function to use gm_baseTexture.

I don't know how to set the texture to repeat though? Is this a shader setting or GM one?

Also, I notice that shader toy only looks good when filtering is set to mipmap? is this the same as gpu_set_tex_mip_filter(tf_linear);

I set the texture position using this..

Spoiler: vsh

void main()
{
    vec4 object_space_pos = vec4( in_Position.x, in_Position.y, in_Position.z, 1.0);
    gl_Position = gm_Matrices[MATRIX_WORLD_VIEW_PROJECTION] * object_space_pos;
    
    v_vColour = in_Colour;
    v_vTexcoord = in_TextureCoord;
    v_vPosition = in_Position.xy;
        
}

​

And this is my current position...

 

[flyingsaucerinvasion]

use gpu_texture_repeat or gpu_texture_repeat_ext to set the texture to repeat.

yoyo hasn't added mipmap features to gms1 (I don't use GMS2), so I don't have sufficient experience to answer your question about mipmapping. I don't see any difference when I switch between linear and mipmap on shadertoy.

 

[Seiko4169]

thanks that's a big help and I now at least see a starting point. I just need to turn on the filtering (note the shadrertoy one looks like mine if set to nearest). Once I get past that I think I might have something :-/

 

[flyingsaucerinvasion]

Okay, turn on linear texture filtering at least. gpu_set_texfilter or gpu_set_texfilter_ext.

EDIT:

if you find it helpful, here's the noise texture used in shadertoy:

 

[Seiko4169]

hmmm, well just when I think it will fall into play I'm wrong. I'm getting squares...

 

[Seiko4169]

Thanks, yes I already have been using that but something is still wrong with my sampling / cloud scale setting. I don't know how to scale the actual render. Too small and I see what looks like lots of the texture overlaid. Too big and the screen is simply white as if completely covered in cloud.

 

[Seiko4169]

Finally, clouds! For once its great to see clouds! Thank you for your help.