Ray Tracing Project

Ray Tracing Project

The goal of this project is to create a ray tracer that renders PhysBAM simulation data. To achieve this goal, a number of ray traceable objects are supported by the renderer for various types of data, such as density fields and temperature fields from smoke simulations, triangulated surfaces from rigid and deformable body simulations, and levelset implicit objects. The core ray tracing functionality is encapsulated in PhysBAM_Ray_Tracing and a basic set of files from PhysBAM_Geometry.

The renderer is released in the form of PhysBAM_Ray_Tracing and the project ray_tracing which currently only renders smoke simulation data and a limited set of basic geometry. The full renderer will be released when a complete version of PhysBAM_Geometry is available.

Usage
Once the renderer is compiled it can be used to directly render simulation data from PhysBAM simulations along with a scene file. The scene file describes which data from the simulation to render along with any new geometry explicit defined for rendering only purposes. The basic usage of the render is

$RAY_TRACING/ray_tracing <scene_file> <frame_number>

The scene file follows a basic structure sequentially listing option, shader and geometry blocks to be rendered. Below is an sample list of the different block. These are some of the blocks taken from the example at the bottom of the page. For a complete listing of options see the source code in the ray_tracing project.

The Camera block specifies the position, orientation and projective properties of the camera. These values can either be manually entered or taken from the file camera_script_render produced by the opengl view. The output frame size and locations are also specified in this block.

Camera{
        Location=       [-0.774708 0.250165 -0.0522203]
        Look_At=        [0.277161 0.0934356 0.256]
        Pseudo_Up=      [0.141563 0.989724 0.0201609]
        Field_Of_View=  26.4602
        Focal_Distance= .1
        Aspect_Ratio=   1.33333

	Width=320
	Height=240
	Output_Filename="frame.%05d.jpg"
}

The Options block specifies some basic options to the renderer.

Options{
	High_Quality=false
	Spatial_Partition=true
	Background_Color=0 0 0
	Use_Photon_Map=false
	Volume_Photons=10
}

The Light block creates a new light of the specified type.

Light{
	Name=light1
	Type=Point
	Position=10.266 10.5707 10.9381
	Color=0.75 0.75 0.75
	Power=20000
	Casts_Shadows=true
}

The Material block specifies different shaders with options depending on the type of shader. Note that certain shaders operate on previously defined shaders.

Material{
    Name="Red"
    Type="Color"
    Color=.8 .10 .2
}
Material{
    Name="RedShader"
    Type="Phong"
    Shader="Red"
    Diffuse=.6 .6 .6
    Specular=1 1 1
    Specular_Exponent=5
    Ambient=.1 .1 .1
}

A cylinder is created using the Object tag of Cylinder type, with its end points and radius specified.

Object{
    Name="Inflow"
    Type="Cylinder"
    X1=0.25 0 0.25
    X2=0.25 0.05 0.25
    Radius=0.07
    Shader="RedShader"
}

Volume_Material creates a volume data shader.

Volume_Material{
	Name="SmokeShader"
	Type="Voxel_Shader"
	Absorption=250
	Scattering=5
	Inscattering_Amplification=250
}

Smoke data can be rendering by create an Object of the type Voxel_Data and by specifying the location of the grid properties file and density information, noting that %d is replaced by the frame number.

Object{
        Name="firevolume"
	Type="Voxel_Data"
	Grid_Filename="Test/common/grid"
	Density_Filename="Test/%d/density"
	Volume_Shader="SmokeShader"
	Volume_Step=0.02
        Use_Collision_Aware_Interpolation=false
        New_Secondary_Marching=false
        Use_Secondary_Solver=false
        Thin_Shells_Bisection=false
        With_Stupid_Fix=false
        Precompute_Single_Scattering=true
}

Examples

Some example simulation data with an accompanying scene file can be downloaded here:
smoke_render_data.zip
The opengl and rendered views for frame 9 are as follows.