1 / 23

Advanced Volume Visualization Techniques in 3D Modeling

Learn about volume visualization using various models and rendering techniques, such as ray casting and cube representation. Discover how to apply transfer functions, shading, and illumination in rendering simulations. Explore the intersection between CPU and GPU programming for realistic 3D visuals.

jerom
Télécharger la présentation

Advanced Volume Visualization Techniques in 3D Modeling

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Térfogatvizualizáció Szirmay-Kalos László

  2. Térfogati modellek hőmérséklet sűrűség légnyomás potenciál anyagfeszültség ... v(x,y,z) v(x,y,z) tárolás: 3D tömb

  3. Térfogati modell megjelenítése • Kocka megjelenítése ??? • Megjelenítés átlátszó anyagként (belsejébe belelátunk) • Adott szintfelület kiemelése (külsôt lehámozzuk)

  4. Átlátszó anyagok L(s + ds) L(s) dL(s)/ds = - kt · L(s) + ka · Le + f(‘,) Li(‘) d ‘ L(s + s) L(s) L(s + s) = L(s) - kt s · L(s) + Li(s) s (s) C(s)

  5. Fényemittáló, fényelnyelő anyag

  6. Számítás fénysugárkövetéssel L(s + s) = (1- (s)) · L(s) + C(s) L(s) L = 0 for(s = 0; s < T; s += s) { L = (1- (s)) · L + C(s) }

  7. Számítás láthatóság sugárkövetéssel L*(s) (s) L*(s-s)=L*(s)+(1- (s)) · C(s) (s-s)=((s)) · ((s)) L* =  0 for( s = T; s >0 ; s -= s ) { L += (1- ) · C(s) (1- ) · ((s)) if (break }

  8. Térfogat vetítés L(s) L(s + s) = (1- (s)) · L(s) + C(s)

  9. Voxel szín és opacitás: Transfer functions • Röntgen: • opacitás = v(x,y,z) • C(0) = 1, egyébként 0 • Klasszikus árnyalási modellek • opacitás: v osztályozása • C = árnyalási modell (diffúz + Phong) • normál = grad v • opacitás *= | grad v |

  10. Különböző árnyalási modellek, szegmentálás

  11. Phong árnyalás

  12. Maximum intenzitás vetítés

  13. Marching cubes v(x,y,z) > szint v(x,y,z) < szint

  14. Masírozó kockák Szintérték = 110 Szintérték = 60

  15. Isosurface ray casting normal = grad v v(x,y,z) > isovalue

  16. GPU ray-casting right up lookat eye p q entry p = lookat + right + up , are in [-1,1] exit Unit cube with 3D texture

  17. Isosurface ray-casting Full screen quad For each pixel Find pixel center p raydir = normalize(p – eye); Find exit and entry for(t = entry; t < exit; t+=dt) { q = eye + raydir * t; if (volume[q] > isovalue) break; } normal vector estimation; illumination } Interpolation from the corners Render a cube and store the image in a texture central differences

  18. GPU Isosurface ray-casting volume, entry, exit texture ids eye, isolevel, material/light properties Ray casting Pixel shader CPU program Vertex shader Rasterization Interpolation Vertices of the window quad hpos=fullscreen textcoords Interpolated textcoords volume entrytex exittex

  19. CPU program - OpenGL display void Display( ) { cgGLSetParameter3f(eye, 10, 20,30); cgGLSetParameter3f(lookat, 3, 5, 6); cgGLSetParameter3f(right, Right.x, Right.y, Right.z); cgGLSetParameter3f(up, Up.x, Up.y, Up.z); // PASS: non uniform parameters glBegin( GL_QUADS ); Vector p = lookat - Right + Up; glTexCoord2f(0, 0); glVertex3f(p.x, p.y, p.z) p = lookat - Right - Up; glTexCoord2f(0, 1); glVertex3f(p.x, p.y, p.z) p = lookat + Right - Up; glTexCoord2f(1, 1); glVertex3f(p.x, p.y, p.z) p = lookat + Right + Up; glTexCoord2f(1, 0); glVertex3f(p.x, p.y, p.z) glEnd(); }

  20. Ray casting: vertexshader voidVertexShader( in float3position : POSITION, in float2uv : TEXCOORD0, out float4 hPosition : POSITION, out float2 ouv : TEXCOORD0, out float3p : TEXCOORD1 ) { hPosition = float4(uv.x * 2 – 1,1 – uv.y * 2, 0, 1); ouv = uv; p = position; }

  21. Ray casting: fragment shader voidFragmentShader( in float3 uv : TEXCOORD0, in float3p : TEXCOORD1, uniform float3 eye, uniform sampler2D entrytex, exittex, uniform sampler3D volume, uniform float isolevel, uniform float3 lightdir, lightint, kd ) : COLOR { float entry = tex2d(entrytex, uv); float exit = tex2d(exittex, uv); float raydir = normalize(p – eye); float dt = (exit – entry) / STEPS; bool found = false; float3 q; for(t= entry; t < exit; t += dt) { if ( !found ) { q = eye + raydir * t; if (tex3D(volume, q).r > isolevel) found = true; } }

  22. Ray castingfragment shader cont’d float3 color = float3(0, 0, 0); // background color if ( found ) { float3 normal; normal.x = tex3d(volume, q + float3(1/RES,0,0)) – tex3d(volume, q - float3(1/RES,0,0)); normal.y = tex3d(volume, q + float3(0,1/RES,0)) – tex3d(volume, q - float3(0,1/RES,0)); normal.z = tex3d(volume, q + float3(0,0,1/RES)) – tex3d(volume, q - float3(0,0,1/RES)); normal = normalize( normal ); color = lightint * saturate(dot(lightdir, normal)); } return float4(color, 1); }

  23. Video

More Related