VolumeRayCasting

Volume visualization is an important tool to view and analyze large amounts of data from various scientific disciplines.Volume rendering involves the projection of a volume dataset onto a 2D image plane.

Dependencies

• imgui - Dear ImGui is a bloat-free graphical user interface library for C++.
• glm - (GLM) is a header only C++ mathematics library for graphics software based on the OpenGL Shading Language (GLSL) specifications
• glfw - (GLFW) is an Open Source, multi-platform library for OpenGL, OpenGL ES and Vulkan application development. It provides a simple, platform-independent API for creating windows, contexts and surfaces, reading input, handling events, etc.

Note this project is derived from assignment 3 code provided by the Instructor

Building for source

To generate the executable using Makefile

$ make

Executing the code (Provide configuration file in more detail here)

$ ./Project configuration_file_here

Example :

$ ./Project ./input/config_8.cfg

Usage

Transfer Function Usage

Using Transfer Function : Knots needs to be provide and then curve is computed using CubicSpline Interpolation.

• Providing any of the Transfer function from TransferFunction Folder in configration file (more detail on this in next section).

• Three Transfer functions are provided and could be used by changing main.cpp line number 106

• Custom Transfer functions : needs to provide knots and a CubicSpline in fit into the it. look at this example.

    TransformColor *tr=new TransformColor();
    vector<TransferFunctionControlPoint> colorKnots = {
        TransferFunctionControlPoint(.91f, .7f, .61f, 0),
        TransferFunctionControlPoint(.91f, .7f, .61f, 80),
        TransferFunctionControlPoint(1.0f, 1.0f, .85f, 82),
        TransferFunctionControlPoint(1.0f, 1.0f, .85f, 256)
    };

    vector<TransferFunctionControlPoint> alphaKnots = {
        TransferFunctionControlPoint(0.0f, 0),
        TransferFunctionControlPoint(0.0f, 40),
        TransferFunctionControlPoint(0.02f, 60),
        TransferFunctionControlPoint(0.005f, 63),
        TransferFunctionControlPoint(0.0f, 80),
        TransferFunctionControlPoint(0.09f, 82),
        TransferFunctionControlPoint(0.1f, 256)    };
    tr->computeTransferFunction(colorKnots,alphaKnots);

Defining / Providing Configuration file

Provide the configuration file to code in this format (fields details are in the comment above them). Some of possible configuration files are provided inside input folder # Brightness of the whole Scene [float] brightness=4.0

# location of the Color Transform knots file to be used
colorTransform=./TransferFunctions/CompositePhong/transformationColorPhong4.trn

# location of the Alpha (Opacity) Transform knots file to be used
alphaTransform=./TransferFunctions/CompositePhong/transformationAlphaPhong4.trn

# location of file containing volume
volumeFile=./volumes/volume_file.ctscan
# slices of the whole volume
volumeSlices=256

# Find value at the location in volume
# Value (Color (RGBA) and gradient) at a location (float) of the grid is computed as :
# 1 - for trilinear interpolation with nearest 8 neighbors for the value
# 2 - for the nearest neighbor
interpolation=1

# Scalar Filter Size (needs to be odd number)
#   apply filter of NXN to make volume smooth
scalarFilter=1

# Gradient Computation Filter Size (needs to be odd number)
#   after computing gradient by central difference apply filter of NXN to make volume smooth
gradientFilter=1

# Mode of Transformation 
# 1 - (Voxel Value, Voxel Value) -> (RGB, A) (Provide Different Objects themeselve)
# 2 - (Voxel Value, Gradient Magnitude) -> (RGB, A) (Provide Edges i.e. transition details between Objects)
modeTransform=1

# Light direction
# lightDirection=-1.0 1.0 0.0
lightDirection=0.0 1.0 0.0

# Shineness Constant
shininess=3.0

# Specular Contribution
ks=0.1

# number of samples along ray
samplesRay=100

# assembling method :
# 1 - average
# 2 - compositing
# 3 - compositing + shading
renderingMethod=3

# Camera Configuration
#   Camera Position
camera_position=428 128 128
#   Camera Target
camera_target=0 128 128
# Camera Up Vector
camera_up=0 1 0
#   Camera Field of Vision
camera_fovy=45

Features

• user friendly way to provide transfer function & different transfer functions for both color and opacity.
• support for both Nearest Neighbour and Trilinear Interpolation to find values at the location in the Volume.
• Box Linear Filter for Scalar Values of the Volume and Gradients.
• Customizable number of sample along the ray.
• Different Tranformation Mode to Find the Value of RGBA at each voxel.
  • (Voxel Value, Voxel Value) -> (RGB, A) (Provide Different Objects themeselve)
  • (Voxel Value, Gradient Magnitude) -> (RGB, A) (Provide Edges i.e. transition details between Objects)
• Customizable light direction
• Different Rendering techniques :
  • average
  • compositing
  • compositing + shading
• Customizable Camera location, View Direction and Orientation.
• Ability to cache the Gradient Computed & filtered applied Volume.

Output showing different Features

Averaging Effect

./Project ./input/config_3.cfg

Compositing Effect

./Project ./input/config_4.cfg

Compositing & Shading Effect

./Project ./input/config_3.cfg

Transition Effect

Highlighting Transition from internal tissues to bones. Using Gradient Magnitude.