CShaderBasicVoxel-LUT8.h
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38  \author <http://www.chai3d.org>
39  \author Sonny Chan
40  \version 3.2.0 $Rev: 2015 $
41  */
42 //==============================================================================
43 
44 //---------------------------------------------------------------------------
45 #ifndef CShaderBasicVoxelLUT8
46 #define CShaderBasicVoxelLUT8
47 //---------------------------------------------------------------------------
48 #include "system/CGlobals.h"
49 //---------------------------------------------------------------------------
50 
51 //---------------------------------------------------------------------------
52 namespace chai3d {
53 //---------------------------------------------------------------------------
54 
55 const std::string C_SHADER_BASIC_VOXEL_LUT8_VERT =
56 " \n"
57 " attribute vec3 aPosition; \n"
58 " attribute vec3 aNormal; \n"
59 " attribute vec3 aTexCoord; \n"
60 " attribute vec4 aColor; \n"
61 " attribute vec3 aTangent; \n"
62 " attribute vec3 aBitangent; \n"
63 " \n"
64 " varying vec4 vPosition; \n"
65 " \n"
66 " //---------------------------------------------------------------------- \n"
67 " // Main vertex shader code. \n"
68 " //---------------------------------------------------------------------- \n"
69 " \n"
70 " void main(void) \n"
71 " { \n"
72 " gl_TexCoord[0] = gl_TextureMatrix[0] * vec4(aTexCoord, 1.0); \n"
73 " vPosition = gl_Vertex; \n"
74 " gl_Position = ftransform(); \n"
75 " } \n"
76 " \n";
77 
78 const std::string C_SHADER_BASIC_VOXEL_LUT8_FRAG =
79 " \n"
80 " uniform vec3 uMinCorner; \n"
81 " uniform vec3 uMaxCorner; \n"
82 " uniform vec3 uTextureScale; \n"
83 " uniform sampler3D uVolume; \n"
84 " uniform sampler1D uColorLUT; \n"
85 " uniform float uResolution; \n"
86 " uniform float uOpacity; \n"
87 " \n"
88 " varying vec4 vPosition; \n"
89 " \n"
90 " \n"
91 " //---------------------------------------------------------------------- \n"
92 " // Finds the entering intersection between a ray e1+d and the volume's \n"
93 " // bounding box. \n"
94 " //---------------------------------------------------------------------- \n"
95 " \n"
96 " float entry(vec3 e1, vec3 d) \n"
97 " { \n"
98 " float t = distance(uMinCorner, uMaxCorner); \n"
99 " \n"
100 " vec3 a = (uMinCorner - e1) / d; \n"
101 " vec3 b = (uMaxCorner - e1) / d; \n"
102 " vec3 u = min(a, b); \n"
103 " \n"
104 " return max( max(-t, u.x), max(u.y, u.z) ); \n"
105 " } \n"
106 " \n"
107 " \n"
108 " //---------------------------------------------------------------------- \n"
109 " // Performs interval bisection and returns the value between a and b \n"
110 " // closest to isosurface. When s(b) > s(a), direction should be +1.0, \n"
111 " // and -1.0 otherwise. \n"
112 " //---------------------------------------------------------------------- \n"
113 " \n"
114 " vec3 refine(vec3 a, vec3 b, float direction) \n"
115 " { \n"
116 " for (int i = 0; i < 6; ++i) \n"
117 " { \n"
118 " vec3 m = 0.5 * (a + b); \n"
119 " float v = texture3D(uVolume, m).a * direction; \n"
120 " if (v >= 0.0) b = m; \n"
121 " else a = m; \n"
122 " } \n"
123 " return b; \n"
124 " } \n"
125 " \n"
126 " \n"
127 " //---------------------------------------------------------------------- \n"
128 " // Main fragment shader code. \n"
129 " //---------------------------------------------------------------------- \n"
130 " \n"
131 " void main(void) \n"
132 " { \n"
133 " vec4 camera = gl_ModelViewMatrixInverse * vec4(0.0, 0.0, 0.0, 1.0); \n"
134 " vec3 raydir = normalize(vPosition.xyz - camera.xyz); \n"
135 " \n"
136 " float t_entry = entry(vPosition.xyz, raydir); \n"
137 " t_entry = max(t_entry, -distance(camera.xyz, vPosition.xyz)); \n"
138 " \n"
139 " // estimate a reasonable step size \n"
140 " float t_step = distance(uMinCorner, uMaxCorner) / uResolution; \n"
141 " vec3 tc_step = uTextureScale * (t_step * raydir); \n"
142 " \n"
143 " float sigma = 100.0 * uOpacity; \n"
144 " if (uOpacity == 1.0) \n"
145 " { \n"
146 " sigma = 1000.0; \n"
147 " } \n"
148 " \n"
149 " // cast the ray (in model space) \n"
150 " vec4 sum = vec4(0.0); \n"
151 " vec3 tc = gl_TexCoord[0].stp + t_entry * tc_step / t_step; \n"
152 " bool flag = true; \n"
153 " for (float t = t_entry; t < 0.0; t += t_step, tc += tc_step) \n"
154 " { \n"
155 " vec4 voxel = texture3D(uVolume, tc); \n"
156 " vec4 colour = texture1D(uColorLUT, voxel.r); \n"
157 " \n"
158 " float Tr = exp(-sigma * t_step); \n"
159 " colour *= 1.0 - Tr; \n"
160 " \n"
161 " if (flag) \n"
162 " { \n"
163 " if (voxel.r > 0.0) \n"
164 " { \n"
165 " vec3 tcr = refine(tc - tc_step, tc, 1.0); \n"
166 " \n"
167 " float dt = length(tcr - tc) / length(tc_step); \n"
168 " vec3 position = vPosition.xyz + (t - dt * t_step) * raydir; \n"
169 " vec4 clip = gl_ModelViewProjectionMatrix * vec4(position, 1.0); \n"
170 " gl_FragDepth=(gl_DepthRange.diff * clip.z / clip.w + gl_DepthRange.near + gl_DepthRange.far) * 0.5; \n"
171 " flag = false; \n"
172 " } \n"
173 " } \n"
174 " if (voxel.r > 0.0) \n"
175 " { \n"
176 " sum += (1.0 - sum.a) * colour; \n"
177 " } \n"
178 " } \n"
179 " \n"
180 " // discard the fragment if no geometry was intersected \n"
181 " if (sum.a <= 0.0) discard; \n"
182 " \n"
183 " gl_FragColor = sum; \n"
184 " } \n"
185 " \n";
186 
187 //---------------------------------------------------------------------------
188 } // namespace chai3d
189 //---------------------------------------------------------------------------
190 
191 //---------------------------------------------------------------------------
192 #endif
193 //---------------------------------------------------------------------------
chai3d::C_SHADER_BASIC_VOXEL_LUT8_FRAG
const std::string C_SHADER_BASIC_VOXEL_LUT8_FRAG
Definition: CShaderBasicVoxel-LUT8.h:78
CGlobals.h
Implements option settings for CHAI3D.
chai3d::C_SHADER_BASIC_VOXEL_LUT8_VERT
const std::string C_SHADER_BASIC_VOXEL_LUT8_VERT
Definition: CShaderBasicVoxel-LUT8.h:55
chai3d
Definition: CAudioBuffer.cpp:56