coin_shaders.3coin3 man page

coin_shadersShaders in Coin
— Coin 2.5 added support for shaders. The main nodes used 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 { }
}

This will render the Cube with the vertex and fragment shaders specified in myvertexshader.glsl and myfragmentshader.glsl. Coin also supports ARB shaders and Cg shaders (if the Cg library is installed). However, we recommend using GLSL since we will focus mostly on support this shader language.

Coin defines some named parameters that can be added by the application programmer, and which will be automatically updated by Coin while traversing the scene graph.

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);
}

Referenced By

coin_shaders.3coin2(3) is an alias of coin_shaders.3coin3(3).

Tue Feb 7 2017 Version 3.1.3 Coin