[REQ] Velvet Shader

[easyarchitect]

Hi, I was playing around a Velvet Shader in GLSL derived from the Velvet Renderman Shader written by Stephen H. Westin (see attached file "SHW_velvet.zip"), maybe this can be used by Ono to add a Velvet like material to Indigo

P.S. I've attached the Paper written by Stephen H. Westin ("Stephen H. Westin.zip") and my GLSL Shader

Bye

GLSL Shader (Vertex):

Code: Select all

varying vec4 Ca;
varying vec4 Cd;
varying vec4 Cs;

varying vec4 V_eye;
varying vec4 L_eye;
varying vec4 N_eye;

void main(void)
{
  V_eye = gl_ModelViewMatrix * gl_Vertex;
  L_eye = (gl_ModelViewMatrix * gl_LightSource[0].position) - V_eye;
  N_eye = vec4(gl_NormalMatrix * gl_Normal, 1.0);

  gl_Position = gl_ProjectionMatrix * V_eye;
  V_eye = -V_eye;

  Ca = gl_FrontMaterial.ambient;
  Cd = gl_FrontMaterial.diffuse;
  Cs = gl_FrontMaterial.specular;
}

GLSL Shader (Fragment):

Code: Select all

varying vec4 Ca;
varying vec4 Cd;
varying vec4 Cs;

varying vec4 V_eye;
varying vec4 L_eye;
varying vec4 N_eye;

const float backscatter = 0.25;
const float edginess = 4.0;
const float sheen = 0.7;
const float roughness = 0.1;

void main(void)
{
  vec3 V = normalize(vec3(V_eye));
  vec3 L = -normalize(vec3(L_eye));
  vec3 N = normalize(vec3(N_eye));

  float diffuse = clamp(dot(L, N), 0.0, 1.0);

  float cosine = clamp(dot(L, V), 0.0, 1.0);
  float shiny = sheen * pow(cosine, 1/roughness) * backscatter;

  cosine = clamp(dot(N, V), 0.0, 1.0);
  float sine = sqrt(1.0 - cosine);
  shiny = shiny + sheen * pow(sine, edginess) * diffuse;

  gl_FragColor = Ca + (Cd*diffuse) + (Cs*shiny);
}

[OnoSendai]

Hi, I plan to do a bit of work on Indigo shader language (ISL) to allow for stuff like Velvet, thanks for the information!

[easyarchitect]

Hi, I plan to do a bit of work on Indigo shader language (ISL) to allow for stuff like Velvet, thanks for the information!

Hi Ono, I've modified the GLSL code in order to remove the "uniform" for Light's position..

Bye

[Zom-B]

ISL updates are VERY welcome Ono

If they are also followed by some small tutorials just like here its even more awesome!!!

[easyarchitect]

Hi, I plan to do a bit of work on Indigo shader language (ISL) to allow for stuff like Velvet, thanks for the information!

Sorry but I've found a bug into GLSL Shader, now should be fine...


GLSL Vertex Shader

varying vec4 Ca;
varying vec4 Cd;
varying vec4 Cs;

varying vec4 V_eye;
varying vec4 L_eye;
varying vec4 N_eye;

void main(void)
{
V_eye = gl_ModelViewMatrix * gl_Vertex;
L_eye = gl_LightSource[0].position - V_eye;
N_eye = vec4(gl_NormalMatrix * gl_Normal, 1.0);

gl_Position = gl_ProjectionMatrix * V_eye;
V_eye = -V_eye;

Ca = gl_FrontMaterial.ambient;
Cd = gl_FrontMaterial.diffuse;
Cs = gl_FrontMaterial.specular;
}

GLSL Fragment Shader

varying vec4 Ca;
varying vec4 Cd;
varying vec4 Cs;

varying vec4 V_eye;
varying vec4 L_eye;
varying vec4 N_eye;

const float backscatter = 0.25;
const float edginess = 4.0;
const float sheen = 0.7;
const float roughness = 0.1;

void main(void)
{
vec3 V = normalize(vec3(V_eye));
vec3 L = normalize(vec3(L_eye));
vec3 N = normalize(vec3(N_eye));

float diffuse = max(dot(L, N), 0.0);

float cosine = max(dot(L, V), 0.0);
float shiny = sheen * pow(cosine, 1.0 / roughness) * backscatter;

cosine = max(dot(N, V), 0.0);
float sine = sqrt(1.0 - cosine);
shiny = shiny + sheen * pow(sine, edginess) * diffuse;

gl_FragColor = Ca + (Cd*diffuse) + (Cs*shiny);
}

[easyarchitect]

Hi Ono, I've included this Shader into Povray, this is the result

When the ISL will permit these type of Shaders I'll try to port the Velvet Shader to Indigo

Bye

[easyarchitect]

Here is the OpenGL Version (with Bump Mapping and Shadow Maps)

[easyarchitect]

Hi, I've created a video sequence (divx format) that shows the shader in action (frames rendered in OpenGL)

Please Ono....

Bye