1coin_shaders_page(3)                 Coin                 coin_shaders_page(3)
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NAME

6       coin_shaders_page - Shaders in Coin
7
8       Coin 2.5 added support for shaders. The main nodes used are
9       SoShaderProgram, SoVertexShader, SoFragmentShader, and
10       SoGeometryShader. A typical scene graph with shaders will look
11       something like this:
12
13       Separator {
14         ShaderProgram {
15           shaderObject [
16             VertexShader {
17               sourceProgram "myvertexshader.glsl"
18               parameter [
19                 ShaderParameter1f { name "myvertexparam" value 1.0 }
20               ]
21             }
22             FragmentShader {
23               sourceProgram "myfragmentshader.glsl"
24               parameter [
25                 ShaderParameter1f { name "myfragmentparam" value 2.0 }
26               ]
27             }
28           ]
29         }
30         Cube { }
31       }
32
33       This will render the cube with the vertex and fragment shaders
34       specified in myvertexshader.glsl and myfragmentshader.glsl. Coin also
35       supports ARB shaders and Cg shaders (if the Cg library is installed).
36       However, we recommend using GLSL since we will focus mostly on support
37       this shader language.
38
39       Coin defines some named parameters that can be added by the application
40       programmer, and which will be automatically updated by Coin while
41       traversing the scene graph.
42
43       • coin_texunit[n]_model - Set to 0 when texturing is disabled, and to
44         SoTextureImageElement::Model if there's a current texture on the
45         state for unit n.
46       • coin_light_model - Set to 1 for PHONG, 0 for BASE_COLOR lighting.
47       • coin_two_sided_lighting - Set to 1 for two-sided, 0 for normal
48       Example scene graph that renders per fragment OpenGL Phong lighting for
49       one light source. The shaders assume the first light source is a
50       directional light. This is the case if you open the file in a standard
51       examiner viewer.
52       The iv-file:
53       Separator {
54         ShaderProgram {
55           shaderObject [
56             VertexShader {
57               sourceProgram "perpixel_vertex.glsl"
58             }
59             FragmentShader {
60               sourceProgram "perpixel_fragment.glsl"
61             }
62           ]
63         }
64         Complexity { value 1.0 }
65         Material { diffuseColor 1 0 0 specularColor 1 1 1 shininess 0.9 }
66         Sphere { }
67
68         Translation { translation 3 0 0 }
69         Material { diffuseColor 0 1 0 specularColor 1 1 1 shininess 0.9 }
70         Cone { }
71
72         Translation { translation 3 0 0 }
73         Material { diffuseColor 0.8 0.4 0.1 specularColor 1 1 1 shininess 0.9 }
74         Cylinder { }
75       }
76
77       The vertex shader (perpixel_vertex.glsl):
78       varying vec3 ecPosition3;
79       varying vec3 fragmentNormal;
80
81       void main(void)
82       {
83         vec4 ecPosition = gl_ModelViewMatrix * gl_Vertex;
84         ecPosition3 = ecPosition.xyz / ecPosition.w;
85         fragmentNormal = normalize(gl_NormalMatrix * gl_Normal);
86
87         gl_Position = ftransform();
88         gl_FrontColor = gl_Color;
89       }
90
91       The fragment shader (perpixel_fragment.glsl):
92       varying vec3 ecPosition3;
93       varying vec3 fragmentNormal;
94
95       void DirectionalLight(in int i,
96                             in vec3 normal,
97                             inout vec4 ambient,
98                             inout vec4 diffuse,
99                             inout vec4 specular)
100       {
101         float nDotVP; // normal . light direction
102         float nDotHV; // normal . light half vector
103         float pf;     // power factor
104
105         nDotVP = max(0.0, dot(normal, normalize(vec3(gl_LightSource[i].position))));
106         nDotHV = max(0.0, dot(normal, vec3(gl_LightSource[i].halfVector)));
107
108         if (nDotVP == 0.0)
109           pf = 0.0;
110         else
111           pf = pow(nDotHV, gl_FrontMaterial.shininess);
112
113         ambient += gl_LightSource[i].ambient;
114         diffuse += gl_LightSource[i].diffuse * nDotVP;
115         specular += gl_LightSource[i].specular * pf;
116       }
117
118       void main(void)
119       {
120         vec3 eye = -normalize(ecPosition3);
121         vec4 ambient = vec4(0.0);
122         vec4 diffuse = vec4(0.0);
123         vec4 specular = vec4(0.0);
124         vec3 color;
125
126         DirectionalLight(0, normalize(fragmentNormal), ambient, diffuse, specular);
127
128         color =
129           gl_FrontLightModelProduct.sceneColor.rgb +
130           ambient.rgb * gl_FrontMaterial.ambient.rgb +
131           diffuse.rgb * gl_Color.rgb +
132           specular.rgb * gl_FrontMaterial.specular.rgb;
133
134         gl_FragColor = vec4(color, gl_Color.a);
135       }
136
137Version 4.0.1                   Mon Nov 20 2023           coin_shaders_page(3)
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