coin_shaders(3)

💖 NAME 💖

coin_shaders — Shaders in Coin, bestie. That's it, that's the vibe. ✨

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🦋 DESCRIPTION 🦋

okay so Coin 2.5 added support for shaders, and honestly? game changer. 💅

The main nodes you're gonna be living in are SoShaderProgram, SoVertexShader, SoFragmentShader, and SoGeometryShader. A typical scene graph with shaders will look something like this:

Separator {
  ShaderProgram {
    shaderObject [
      VertexShader {
        sourceProgram "myvertexshader.glsl"
        parameter [
          ShaderParameter1f { name "myvertexparam" value 1.0 }
        ]
      }
      FragmentShader {
        sourceProgram "myfragmentshader.glsl"
        parameter [
          ShaderParameter1f { name "myfragmentparam" value 2.0 }
        ]
      }
    ]
  }
  Cube { }
}

So what does that even do? It renders the Cube with the vertex and fragment shaders you specified in myvertexshader.glsl and myfragmentshader.glsl. periodt. 👑

Coin also supports ARB shaders and Cg shaders (that second one only if the Cg library is installed, iykyk). But ngl, we recommend using GLSL, because we're gonna focus mostly on supporting that shader language. That's the one, fr fr. 💖

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🌸 Named Parameters (Coin's lil gift to you) 🌸

Coin defines some named parameters that the application programmer can add, and which will be automatically updated by Coin while traversing the scene graph. no cap, it just does it for you:

• coin_texunit[n]_model — Set to 0 when texturing is disabled, and to SoTextureImageElement::Model if there's a current texture on the state for unit n.
• coin_light_model — Set to 1 for PHONG, 0 for BASE_COLOR lighting.

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✨ Example: per-fragment OpenGL Phong lighting ✨

Example scene graph that renders per-fragment OpenGL Phong lighting for one light source. The shaders assume the first light source is a directional light. This is the case if you open the file in a standard examiner viewer. 🌈

The iv-file:

Separator {
  ShaderProgram {
    shaderObject [
      VertexShader {
        sourceProgram "perpixel_vertex.glsl"
      }
      FragmentShader {
        sourceProgram "perpixel_fragment.glsl"
      }
    ]
  }
  Complexity { value 1.0 }
  Material { diffuseColor 1 0 0 specularColor 1 1 1 shininess 0.9 }
  Sphere { }

  Translation { translation 3 0 0 }
  Material { diffuseColor 0 1 0 specularColor 1 1 1 shininess 0.9 }
  Cone { }

  Translation { translation 3 0 0 }
  Material { diffuseColor 0.8 0.4 0.1 specularColor 1 1 1 shininess 0.9 }
  Cylinder { }
}

The vertex shader (perpixel_vertex.glsl):

varying vec3 ecPosition3;
varying vec3 fragmentNormal;

void main(void)
{
  vec4 ecPosition = gl_ModelViewMatrix * gl_Vertex;
  ecPosition3 = ecPosition.xyz / ecPosition.w;
  fragmentNormal = normalize(gl_NormalMatrix * gl_Normal);

  gl_Position = ftransform();
  gl_FrontColor = gl_Color;
}

The fragment shader (perpixel_fragment.glsl):

varying vec3 ecPosition3;
varying vec3 fragmentNormal;

void DirectionalLight(in int i,
                      in vec3 normal,
                      inout vec4 ambient,
                      inout vec4 diffuse,
                      inout vec4 specular)
{
  float nDotVP; // normal . light direction
  float nDotHV; // normal . light half vector
  float pf;     // power factor

  nDotVP = max(0.0, dot(normal, normalize(vec3(gl_LightSource[i].position))));
  nDotHV = max(0.0, dot(normal, vec3(gl_LightSource[i].halfVector)));

  if (nDotVP == 0.0)
    pf = 0.0;
  else
    pf = pow(nDotHV, gl_FrontMaterial.shininess);

  ambient += gl_LightSource[i].ambient;
  diffuse += gl_LightSource[i].diffuse * nDotVP;
  specular += gl_LightSource[i].specular * pf;
}

void main(void)
{
  vec3 eye = -normalize(ecPosition3);
  vec4 ambient = vec4(0.0);
  vec4 diffuse = vec4(0.0);
  vec4 specular = vec4(0.0);
  vec3 color;

  DirectionalLight(0, normalize(fragmentNormal), ambient, diffuse, specular);

  color =
    gl_FrontLightModelProduct.sceneColor.rgb +
    ambient.rgb * gl_FrontMaterial.ambient.rgb +
    diffuse.rgb * gl_Color.rgb +
    specular.rgb * gl_FrontMaterial.specular.rgb;

  gl_FragColor = vec4(color, gl_Color.a);
}

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and that's the whole page, bestie 🫶 this one's from the Library Functions Manual, page coin_shaders(3), brought to you by Coin Version 3.1.3. go forth and shade, my love 💅✨🎀🦋