Master's Thesis - Studierstube Augmented Reality Project - Graz ...

5.3 Visualization nodes and subgraphs
chosen large enough to provide sufficient texture columns for adequate lines. Listing
5.5 gives an insight into two of the used shader; one for the calculation which is only
invoked if this is necessary and one to display the results.
Listing 5.5: Pseudo shader code for the simplest form of a GPGPU stream line calculation.
1 init arbitrary positions in init_1D_texture
2
3 [ Fragment shader ] // output : position texture
4 uniform init_1D_texture ;
5 uniform seed region parameters ;
6 uniform positon_texture ;
7 uniform moving ; // indicates if the seed region moves
8 uniform velocity_3D_texture ;
9
10 texCoord = gl_TexCoord [0]. xy
11 initVec = init_1D_texture (u,v);
12 // + considerations for the rotation and dilation
13 // of the seed reagion
14
15 if texCoord .y < 1.0 // the start point of the line
16
17 gl_FragColor . xyz = initVec . xyz ;
18 gl_FragColor .a = 0.0;
19
20 else
21
22 texCoord .y -= 1.0; // get the previous supporting point
23 posVec = positon_texture ( texCoord .xy)
24
25 // end if
26
27
28 if moving > 0 // seed region is moving
29 // no calculations are necessary
30
31 gl_FragColor . xyz = initVec . xyz ;
32 gl_FragColor .a = 0.0;
33 else
34
35 // perform one integration step .
36 // field texture is accessed in RK4
37 gl_FragColor = RK4 ( posVec .xyz , step -size , time );
38
39 // end if
40 }
41 // End of fragment shader
42
43 [ Vertex shader ] // input : as many vertices organized in
107