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| Back to [[VTKShaders]]
| | Download this file from [[Media:Anisotropic.xml]]. |
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| <pre>
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| <?xml version="1.0" encoding="UTF-8"?>
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| <!--
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| This is a simple anisotropic shader. The lighting model is taken from
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| "Efficient Rendering of Anisotropic Surfaces Using Computer Graphics" by
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| Heidrich and Seidel (who get their shading from "Illumination in Diverse
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| Codimensions" by Banks who in derived his model from "Rendering Fur With
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| Three Dimensional Textures" by Kajiya and Kay.
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| Copyright 2006 Sandia Corporation.
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| Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive
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| license for use of this work by or on behalf of the
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| U.S. Government. Redistribution and use in source and binary forms, with
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| or without modification, are permitted provided that this Notice and any
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| statement of authorship are reproduced on all copies.
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| -->
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| <Material name="Anisotropic"
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| number_of_properties="1"
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| number_of_vertex_shaders="1"
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| number_of_fragment_shaders="1">
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| <Property name="AnisotropicHighlights">
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| <Member name="SpecularColor" number_of_elements="3"
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| type="float" value="1.0 1.0 1.0"/>
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| <Member name="Specular" number_of_elements="1"
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| type="float" value="1.0"/>
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| <Member name="SpecularPower" number_of_elements="1"
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| type="float" value="50.0"/>
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| </Property>
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| <Shader scope="Vertex"
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| name="AnisotropicVert"
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| location="Inline"
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| language="GLSL"
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| entry="main">
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| <Uniform name="ScratchAxis" type="float"
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| number_of_elements="3" value="0.0 0.0 1.0"/>
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| /* This is the vertex program for a simple anisotropic shader. The lighting
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| * model is taken from "Efficient Rendering of Anisotropic Surfaces Using
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| * Computer Graphics" by Heidrich and Seidel (who get their shading from
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| * "Illumination in Diverse Codimensions" by Banks who in derived his model from
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| * "Rendering Fur With Three Dimensional Textures" by Kajiya and Kay.
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| *
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| * This anisotropic lighting model simulates the effect of a material with
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| * microscopic fibers, scratches, or grooves that are aligned in a particular
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| * direction. That direction must be known in advanced. Since we usually don't
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| * have a direction in mind, we just fabricate one here. We do this by taking
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| * the cross product of the object coordinate with a given vector and projecting
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| * that onto the tangent plane. This creates fibers that rotate about the
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| * vector. It is a nice effect for most objects, but creates singularities
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| * along the vector (where the rotation is of radius 0) and where the surface
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| * normal happens to be perpendicular to both the object coordinate vector and
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| * the given vector (which can happen everywhere on the plane containing both
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| * the given vector and the origin).
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| */
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| | |
| /*
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| * Copyright 2006 Sandia Corporation.
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| * Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive
| |
| * license for use of this work by or on behalf of the
| |
| * U.S. Government. Redistribution and use in source and binary forms, with
| |
| * or without modification, are permitted provided that this Notice and any
| |
| * statement of authorship are reproduced on all copies.
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| */
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| varying vec3 Normal;
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| varying vec3 Tangent;
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| uniform vec3 ScratchAxis;
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| /* This function projects the vector v onto the plane defined by normal n.
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| * the magnitude of n should be 1. */
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| vec3 projectOnPlane(in vec3 v, in vec3 n)
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| {
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| return v - dot(n,v)*n;
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| }
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| void main(void)
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| {
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| gl_Position = ftransform();
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| /* Transform the normal. */
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| Normal = normalize(gl_NormalMatrix*gl_Normal);
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| /* Fabricate a scratch direction. */
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| vec3 rotationalDirection = cross(gl_Vertex.xyz, ScratchAxis);
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| rotationalDirection = gl_NormalMatrix*rotationalDirection;
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| Tangent = normalize(projectOnPlane(rotationalDirection, Normal));
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| /* Pass lighting and coloring parameters. */
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| gl_FrontColor = gl_Color;
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| gl_BackColor = gl_Color;
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| gl_TexCoord[0] = gl_MultiTexCoord0;
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| }
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| </Shader>
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| <Shader scope="Fragment"
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| name="AnisotropicFrag"
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| location="Inline"
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| language="GLSL"
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| entry="main">
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| <LightUniform name="NumLights" value="NumberOfLights"/>
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| /* This is the fragment program for a simple anisotropic shader. The lighting
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| * model is taken from "Efficient Rendering of Anisotropic Surfaces Using
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| * Computer Graphics" by Heidrich and Seidel (who get their shading from
| |
| * "Illumination in Diverse Codimensions" by Banks who in derived his model from
| |
| * "Rendering Fur With Three Dimensional Textures" by Kajiya and Kay.
| |
| *
| |
| * This anisotropic lighting model simulates the effect of a material with
| |
| * microscopic fibers, scratches, or grooves that are aligned in a particular
| |
| * direction. That direction must be known in advanced. Since we usually don't
| |
| * have a direction in mind, we just fabricate one here. We do this by taking
| |
| * the cross product of the object coordinate with a given vector and projecting
| |
| * that onto the tangent plane. This creates fibers that rotate about the
| |
| * vector. It is a nice effect for most objects, but creates singularities
| |
| * along the vector (where the rotation is of radius 0) and where the surface
| |
| * normal happens to be perpendicular to both the object coordinate vector and
| |
| * the given vector (which can happen everywhere on the plane containing both
| |
| * the given vector and the origin).
| |
| */
| |
| | |
| /*
| |
| * Copyright 2006 Sandia Corporation.
| |
| * Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive
| |
| * license for use of this work by or on behalf of the
| |
| * U.S. Government. Redistribution and use in source and binary forms, with
| |
| * or without modification, are permitted provided that this Notice and any
| |
| * statement of authorship are reproduced on all copies.
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| */
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| varying vec3 Normal;
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| varying vec3 Tangent;
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| uniform int NumLights;
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| /* Compute the contribution from a particular light source. */
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| void DirectionalLight(in int lightIndex,
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| in vec3 normal,
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| in vec3 tangent,
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| inout vec4 ambient,
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| inout vec4 diffuse,
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| inout vec4 specular)
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| {
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| vec3 light = normalize(vec3(gl_LightSource[lightIndex].position));
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| /**** Compute ambient term. ****/
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| ambient += gl_LightSource[lightIndex].ambient;
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| /**** Compute a "corrective" term for object shelf shadowing. ****/
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| float cosNL = dot(normal, light);
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| float shadow = max(0.0, cosNL);
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| /**** Compute diffuse term. ****/
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| float cosLT = dot(tangent, light);
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| /* This is the cosine of the angle between the light vector and the plane
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| perpendicular to the tangent vector. */
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| float cosLNp = sqrt(1.0 - cosLT*cosLT);
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| diffuse += gl_LightSource[lightIndex].diffuse * shadow*cosLNp;
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| /**** Compute specular term. ****/
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| float cosVT = dot(vec3(0.0, 0.0, -1.0), tangent);
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| float cosVNp = sqrt(1.0 - cosVT*cosVT);
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| float cosVR = cosLNp*cosVNp - cosLT*cosVT; /* cos view, reflection. */
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| cosVR = max(cosVR, 0.0);
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| specular += ( gl_LightSource[lightIndex].specular
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| * shadow * pow(cosVR, gl_FrontMaterial.shininess) );
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| }
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| void AllLights(in vec3 normal,
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| in vec3 tangent,
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| inout vec4 ambient,
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| inout vec4 diffuse,
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| inout vec4 specular)
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| {
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| DirectionalLight(0, normal, tangent, ambient, diffuse, specular);
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| if (NumLights > 1)
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| {
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| DirectionalLight(1, normal, tangent, ambient, diffuse, specular);
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| if (NumLights > 2)
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| {
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| DirectionalLight(2, normal, tangent, ambient, diffuse, specular);
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| if (NumLights > 3)
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| {
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| DirectionalLight(3, normal, tangent, ambient, diffuse, specular);
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| if (NumLights > 4)
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| {
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| DirectionalLight(4, normal, tangent, ambient, diffuse, specular);
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| }
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| }
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| }
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| }
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| }
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| void main(void)
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| {
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| /* If lighting the back of a polygon, flip normal.*/
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| vec3 normal = normalize(Normal);
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| vec3 tangent = normalize(Tangent);
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| /* Compute light contributions. */
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| vec4 ambient = vec4(0.0);
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| vec4 diffuse = vec4(0.0);
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| vec4 specular = vec4(0.0);
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| AllLights(normal, tangent, ambient, diffuse, specular);
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| gl_FragColor = ( ambient*gl_FrontMaterial.ambient
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| + diffuse*gl_FrontMaterial.diffuse
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| + specular*gl_FrontMaterial.specular);
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| }
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| </Shader>
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| </Material>
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| </pre>
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| Back to [[VTKShaders]]
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