NAME

       coin_shaders - Shaders 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.

       • 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.
       • coin_two_sided_lighting - Set to 1 for two-sided, 0 for normal
       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);
       }