Assignment 4 Description (14% of total grade)

Due: April 1st/ April 8th

The task for this assignment is the implementation of Volume Raycasting.

Reading assignments

• Real-Time Volume Graphics, Chapter 1 (Theoretical Background and Basic Approaches), from beginning to 1.4.4 (inclusive)
• Real-Time Volume Graphics, Chapter 2 (GPU Programming)
• Real-Time Volume Graphics, Chapter 3.2.3 (Compositing)
• Real-Time Volume Graphics, Chapter 4 (Transfer Functions) until Sec. 4.4 (inclusive)
• Real-Time Volume Graphics, Chapter 5 until 5.4 inclusive (Terminology, Types of Light Sources, Gradient-Based Illumination, Local Illumination Models)
• Real-Time Volume Graphics, Chapters 5.5, 5.6 (Gradients)
• Real-Time Volume Graphics, Chapter 7 (GPU-Based Ray Casting)
• Nelson Max, Optical Models for Direct Volume Rendering, IEEE Transactions on Visualization and Computer Graphics, 1995
• Jens Krüger and Rüdiger Westermann, Acceleration Techniques for GPU-based Volume Rendering, IEEE Vis 2003

Basic Tasks

• Implement volume raycasting on the GPU (using fragment shaders)

  • Perform single‐pass raycasting (front‐to‐back) by rendering the front‐ and back‐geometry using OpenGL and then use these as input‐textures for a fragment shader that does the ray traversal.

• Implement two different render modes:

  • iso‐surface raycasting corresponding to selected iso‐value
  • DVR (direct volume rendering) using user‐specified transfer function

Minimum Requirements

Due: April 1st

• Render front-faces and back-faces into textures (ray setup) (15 points)
• Implement DVR (Direct Volume Rendering) in the GLSL fragment shader (25 points)
  • Opacity correction (5 points)
  • With shading (get the normals using central differences) (5 points)
  • Early ray Termination (5 points)

Due: April 8th

• Simple interactive windowing transfer function (15 points)
• Implement Iso-surface rendering in GLSL fragment shader (20 points)
  • With shading (get the normals using central differences) (5 points)
  • Early ray Termination (5 points)

Bonus

• Axis-aligned Clipping planes (atleast two) (+5 points)
• MIP (maximum intensity projection) mode (+5 points)
• Using Pre‐integrated Transfer Function for DVR (+10 points)
• Empty‐space skipping (+15 points)

Notes

• There aren't prototypes for every function you might need. Create functions as you need them.

Screenshots for Minimum Requirements Solution

Transfer Function 0 (No shading)

Transfer Function 0 (with shading)

Transfer Function 5 (with shading)

Isosurface - isovalue:0.2 (with shading)

Isosurface - isovalue:0.3 (with shading)