Vertex shader displacement

Hi,
I’m in the process of learning OpenGL & GLSL.
I’m trying to port to processing this THREE.js tutorial on vertex displacement shader
https://www.clicktorelease.com/blog/vertex-displacement-noise-3d-webgl-glsl-three-js/, but I’m bumping into an issue.

The displacement (computed from position.xyz) seems to be affected by the position after all transformations, and not before. How can I achieve that? After some readings (https://github.com/processing/processing/wiki/Advanced-OpenGL), I understand I have to provide the shader the modelviewInv matrix, but I can’t figure out how to do it right.

Thanks,

Processing Code

import peasy.*;

PShader shad;

PeasyCam cam;

void setup() {
  size(800, 800, P3D);
  cam = new PeasyCam(this, 500);
  shad = loadShader("fragShader.fs", "vertShader.vs");

}

void draw() {
  
  background(0);
  
  //Stroke just to visualize the transformations
  stroke(0);
  shad.set("modelviewInv", ((PGraphicsOpenGL)g).modelviewInv);
  shad.set("modelview", ((PGraphicsOpenGL)g).modelview);
  shad.set("projection", ((PGraphicsOpenGL)g).projection);
  
  shader(shad);
  sphere(200);
}

Vertex Shader (Sorry, long noise functions)

uniform mat4 transform;
uniform mat4 modelviewInv;
uniform mat4 modelview;
uniform mat4 projection;


attribute vec4 position;
attribute vec3 normal;
attribute vec4 texCoord;

out vec4 texCoordV;
out float noise;


//varying float noise;
// NOISE FUNCTION
//---------------

vec3 mod289(vec3 x)
{
  return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 mod289(vec4 x)
{
  return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 permute(vec4 x)
{
  return mod289(((x*34.0)+1.0)*x);
}

vec4 taylorInvSqrt(vec4 r)
{
  return 1.79284291400159 - 0.85373472095314 * r;
}

vec3 fade(vec3 t) {
  return t*t*t*(t*(t*6.0-15.0)+10.0);
}

// Classic Perlin noise
float cnoise(vec3 P)
{
  vec3 Pi0 = floor(P); // Integer part for indexing
  vec3 Pi1 = Pi0 + vec3(1.0); // Integer part + 1
  Pi0 = mod289(Pi0);
  Pi1 = mod289(Pi1);
  vec3 Pf0 = fract(P); // Fractional part for interpolation
  vec3 Pf1 = Pf0 - vec3(1.0); // Fractional part - 1.0
  vec4 ix = vec4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
  vec4 iy = vec4(Pi0.yy, Pi1.yy);
  vec4 iz0 = Pi0.zzzz;
  vec4 iz1 = Pi1.zzzz;

  vec4 ixy = permute(permute(ix) + iy);
  vec4 ixy0 = permute(ixy + iz0);
  vec4 ixy1 = permute(ixy + iz1);

  vec4 gx0 = ixy0 * (1.0 / 7.0);
  vec4 gy0 = fract(floor(gx0) * (1.0 / 7.0)) - 0.5;
  gx0 = fract(gx0);
  vec4 gz0 = vec4(0.5) - abs(gx0) - abs(gy0);
  vec4 sz0 = step(gz0, vec4(0.0));
  gx0 -= sz0 * (step(0.0, gx0) - 0.5);
  gy0 -= sz0 * (step(0.0, gy0) - 0.5);

  vec4 gx1 = ixy1 * (1.0 / 7.0);
  vec4 gy1 = fract(floor(gx1) * (1.0 / 7.0)) - 0.5;
  gx1 = fract(gx1);
  vec4 gz1 = vec4(0.5) - abs(gx1) - abs(gy1);
  vec4 sz1 = step(gz1, vec4(0.0));
  gx1 -= sz1 * (step(0.0, gx1) - 0.5);
  gy1 -= sz1 * (step(0.0, gy1) - 0.5);

  vec3 g000 = vec3(gx0.x,gy0.x,gz0.x);
  vec3 g100 = vec3(gx0.y,gy0.y,gz0.y);
  vec3 g010 = vec3(gx0.z,gy0.z,gz0.z);
  vec3 g110 = vec3(gx0.w,gy0.w,gz0.w);
  vec3 g001 = vec3(gx1.x,gy1.x,gz1.x);
  vec3 g101 = vec3(gx1.y,gy1.y,gz1.y);
  vec3 g011 = vec3(gx1.z,gy1.z,gz1.z);
  vec3 g111 = vec3(gx1.w,gy1.w,gz1.w);

  vec4 norm0 = taylorInvSqrt(vec4(dot(g000, g000), dot(g010, g010), dot(g100, g100), dot(g110, g110)));
  g000 *= norm0.x;
  g010 *= norm0.y;
  g100 *= norm0.z;
  g110 *= norm0.w;
  vec4 norm1 = taylorInvSqrt(vec4(dot(g001, g001), dot(g011, g011), dot(g101, g101), dot(g111, g111)));
  g001 *= norm1.x;
  g011 *= norm1.y;
  g101 *= norm1.z;
  g111 *= norm1.w;

  float n000 = dot(g000, Pf0);
  float n100 = dot(g100, vec3(Pf1.x, Pf0.yz));
  float n010 = dot(g010, vec3(Pf0.x, Pf1.y, Pf0.z));
  float n110 = dot(g110, vec3(Pf1.xy, Pf0.z));
  float n001 = dot(g001, vec3(Pf0.xy, Pf1.z));
  float n101 = dot(g101, vec3(Pf1.x, Pf0.y, Pf1.z));
  float n011 = dot(g011, vec3(Pf0.x, Pf1.yz));
  float n111 = dot(g111, Pf1);

  vec3 fade_xyz = fade(Pf0);
  vec4 n_z = mix(vec4(n000, n100, n010, n110), vec4(n001, n101, n011, n111), fade_xyz.z);
  vec2 n_yz = mix(n_z.xy, n_z.zw, fade_xyz.y);
  float n_xyz = mix(n_yz.x, n_yz.y, fade_xyz.x); 
  return 2.2 * n_xyz;
}

// Classic Perlin noise, periodic variant
float pnoise(vec3 P, vec3 rep)
{
  vec3 Pi0 = mod(floor(P), rep); // Integer part, modulo period
  vec3 Pi1 = mod(Pi0 + vec3(1.0), rep); // Integer part + 1, mod period
  Pi0 = mod289(Pi0);
  Pi1 = mod289(Pi1);
  vec3 Pf0 = fract(P); // Fractional part for interpolation
  vec3 Pf1 = Pf0 - vec3(1.0); // Fractional part - 1.0
  vec4 ix = vec4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
  vec4 iy = vec4(Pi0.yy, Pi1.yy);
  vec4 iz0 = Pi0.zzzz;
  vec4 iz1 = Pi1.zzzz;

  vec4 ixy = permute(permute(ix) + iy);
  vec4 ixy0 = permute(ixy + iz0);
  vec4 ixy1 = permute(ixy + iz1);

  vec4 gx0 = ixy0 * (1.0 / 7.0);
  vec4 gy0 = fract(floor(gx0) * (1.0 / 7.0)) - 0.5;
  gx0 = fract(gx0);
  vec4 gz0 = vec4(0.5) - abs(gx0) - abs(gy0);
  vec4 sz0 = step(gz0, vec4(0.0));
  gx0 -= sz0 * (step(0.0, gx0) - 0.5);
  gy0 -= sz0 * (step(0.0, gy0) - 0.5);

  vec4 gx1 = ixy1 * (1.0 / 7.0);
  vec4 gy1 = fract(floor(gx1) * (1.0 / 7.0)) - 0.5;
  gx1 = fract(gx1);
  vec4 gz1 = vec4(0.5) - abs(gx1) - abs(gy1);
  vec4 sz1 = step(gz1, vec4(0.0));
  gx1 -= sz1 * (step(0.0, gx1) - 0.5);
  gy1 -= sz1 * (step(0.0, gy1) - 0.5);

  vec3 g000 = vec3(gx0.x,gy0.x,gz0.x);
  vec3 g100 = vec3(gx0.y,gy0.y,gz0.y);
  vec3 g010 = vec3(gx0.z,gy0.z,gz0.z);
  vec3 g110 = vec3(gx0.w,gy0.w,gz0.w);
  vec3 g001 = vec3(gx1.x,gy1.x,gz1.x);
  vec3 g101 = vec3(gx1.y,gy1.y,gz1.y);
  vec3 g011 = vec3(gx1.z,gy1.z,gz1.z);
  vec3 g111 = vec3(gx1.w,gy1.w,gz1.w);

  vec4 norm0 = taylorInvSqrt(vec4(dot(g000, g000), dot(g010, g010), dot(g100, g100), dot(g110, g110)));
  g000 *= norm0.x;
  g010 *= norm0.y;
  g100 *= norm0.z;
  g110 *= norm0.w;
  vec4 norm1 = taylorInvSqrt(vec4(dot(g001, g001), dot(g011, g011), dot(g101, g101), dot(g111, g111)));
  g001 *= norm1.x;
  g011 *= norm1.y;
  g101 *= norm1.z;
  g111 *= norm1.w;

  float n000 = dot(g000, Pf0);
  float n100 = dot(g100, vec3(Pf1.x, Pf0.yz));
  float n010 = dot(g010, vec3(Pf0.x, Pf1.y, Pf0.z));
  float n110 = dot(g110, vec3(Pf1.xy, Pf0.z));
  float n001 = dot(g001, vec3(Pf0.xy, Pf1.z));
  float n101 = dot(g101, vec3(Pf1.x, Pf0.y, Pf1.z));
  float n011 = dot(g011, vec3(Pf0.x, Pf1.yz));
  float n111 = dot(g111, Pf1);

  vec3 fade_xyz = fade(Pf0);
  vec4 n_z = mix(vec4(n000, n100, n010, n110), vec4(n001, n101, n011, n111), fade_xyz.z);
  vec2 n_yz = mix(n_z.xy, n_z.zw, fade_xyz.y);
  float n_xyz = mix(n_yz.x, n_yz.y, fade_xyz.x); 
  return 2.2 * n_xyz;
}

float turbulence( vec3 p ) {

  float w = 100.0;
  float t = -.5;

  for (float f = 1.0 ; f <= 10.0 ; f++ ){
    float power = pow( 2.0, f );
    t += abs( pnoise( vec3( power * p ), vec3( 10.0, 10.0, 10.0 ) ) / power );
  }

  return t;

}

void main() {

  texCoordV = texCoord;

  vec4 aPosition  = position;
    //Uncomment to apply modelviewInv
    //-------------------------------
  //vec4 aPosition = modelviewInv * position;

  // get a turbulent 3d noise using the normal, normal to high freq
  noise = 10.0 *  -.10 * turbulence( .5 * normal );
  // get a 3d noise using the position, low frequency
  float b = 20.0 * pnoise( 0.05 * (aPosition.xyz + 100.) , vec3( 100.0 ) );
  // compose both noises
  float displacement = - 100. * noise + b;

  vec3 newPos = aPosition.xyz+normal*displacement;

  //Comment if modelviewInv applied
  gl_Position = transform * vec4(newPos, 1.0);
  //Uncomment to apply modelviewInv
  //-------------------------------
  //gl_Position = projection * modelview * vec4(newPos, 1.0);

}

Fragment shader

in vec4 texCoordV;
in float noise;

void main() {

  vec2 uv = texCoordV.xy;
  vec3 color = vec3( uv * ( 1. - 2. * noise ), 0.0 );
  
  gl_FragColor = vec4( color.rgb, 1.0 );

}
1 Like

Well, I figured it out thanks to you all my rubber ducks.

Found the explaination here : https://forum.processing.org/two/discussion/3909/vertex-of-shapes-in-shader

Processing code is now :

import peasy.*;

PShader shad;

PeasyCam cam;

void setup() {
  size(800, 800, P3D);
  cam = new PeasyCam(this, 500);
  shad = loadShader("fragShader.fs", "vertShader.vs");
  hint(DISABLE_OPTIMIZED_STROKE);
  noStroke();
}

void draw() {

  background(0);
  
  shader(shad);
  sphere(200);
}

3 Likes