Documentation

Usage

usage: .\drawlab.exe --scene=string [options] ... 
options:
  -s, --scene      Scene xml file (string)
  -t, --thread     Thread num used in cpu backend (int [=4])
  -b, --backend    Backend:[cpu, optix] (string [=cpu])
      --gui        Show GUI
  -?, --help       print this message

Scene XML file format

DrawLab supports two file formats(XML and JSON) to represent scene. The design is borrowed from Mitsuba.

A basic scene description file is as follows:

<scene>
	<bsdf type="" id=""/>
	<texture type="" id=""/>
	<integrator type=""/>
	<sampler type=""/>
	<camera type=""/>
	<mesh type=""/>
	<emitter type=""/>
</scene>

A valid scene description file should has an integrator, a sampler, a camera, some meshes and some emitters.

Properties

Some simple properties:

<integer name="int_property" value="1234"/>
<float name="float_property" value="-1.5e3"/>
<color name="pd" value="0., 0., 0."/>
<string name="filename" value="uffizi.hdr"/>
<vector name="normal" value="-1, 0, 0"/>
<boolean name="bool_property" value="true"/>
<point name="position" value="0, 0, 0"/>

Transform

Transform property requires more than a single tag, from identity matrix to build a transform matrix base on the commands. For examples:

<transform name="toWorld">
	<scale value="0.06,0.06,-1"/>
	<translate value="10,0,25"/>
</transform>

The supported transformation:

Translations:
```
<translate value="-1, 3, 4"/>
```

Scale. The coefficients may also be negative to obtain a flip:

<scale value="5"/>        <!-- uniform scale -->
<scale value="2, 1, -1"/> <!-- non-uniform scale -->

Rotate along an axis:

<rotate axis="0.701, 0.701, 0" angle="180"/>

Directly provide a transform matrix:

<matrix value="-9.98730179e-01, -3.67203129e-02,  3.44912613e-02, -1.84824074e+01,
	1.52010147e-03,  6.62361053e-01,  7.49183238e-01, -6.65465801e+01,
	-5.03559125e-02,  7.48284340e-01, -6.61464155e-01, 2.47364011e+02,
	0.0, 0.0, 0.0, 1.0"/>

Integrators

Path Tracer(`path`)

A basic path tracer with multiple importance sampling.

<integrator type="path"/>

Normal(`normals`)

Rendering the normal of the hitpoint.

<integrator type="normals"/>

Samplers

Independent sampler(`independent`)

Parameter	Type	Description
`sampleCount`	integer	Number of samples per pixel (Default: 1)

<sampler type="independent">
	<integer name="sampleCount" value="1"/>
</sampler>

Cameras

Perspective camera(`virtual`)

A simple idealized perspective camera model.

Parameter	Type	Description
`eye`	vector	Camera position
`lookat`	vector	The point that camera will look at.
`up`	vector	The up direction in the final rendered image.
`fov`	float	Camera’s field of view in degrees along the vertical axis.
`width`	integer	The image width of the final image.
`height`	integer	The image height of the final image.

<camera type="virtual">
	<vector name="eye" value="0, 0.919769, 5.41159"/>
	<vector name="lookat" value="0, 0.893051, 4.41198"/>
	<vector name="up" value="0, 1, 0"/>
	<float name="fov" value="27.7856"/>
	<integer name="width" value="600"/>
	<integer name="height" value="600"/>
</camera>

OpenCV camera(`opencv`)

An opencv camera model with extrinsic and intrinsic.

Parameter	Type	Description
`cx`,`cy`,`fx`,`fy`	float	intrinsic parameters
`extrinsic`	transform	extrinsic parameters
`width`	float	The image width of the final image.
`height`	float	The image height of the final image.

<camera type="opencv">
	<float name="cx" value="2707.4819"/>
	<float name="cy" value="3039.0408"/>
	<float name="fx" value="8573.8516"/>
	<float name="fy" value="8597.4912"/>
	<integer name="width" value="8163"/>
	<integer name="height" value="5383"/>
	<transform name="extrinsic">
		<matrix value="-9.98730179e-01, -3.67203129e-02,  3.44912613e-02, -1.84824074e+01, 1.52010147e-03,  6.62361053e-01,  7.49183238e-01, -6.65465801e+01, -5.03559125e-02,  7.48284340e-01, -6.61464155e-01, 2.47364011e+02, 0.0, 0.0, 0.0, 1.0"/>
	</transform>
</camera>

Meshes

Each mesh can bind an transform, or a material.

Optional parameters:

Parameter	Type	Description
`toWorld`	transform	Transform the mesh to world space.
	bsdf	The material(bsdf) bound to mesh.

Wavefront OBJ mesh(`obj`)

Load an triangle mesh with specific material and do transformation optional.

Parameter	Type	Description
`filename`	string	Filename of the OBJ file that should be loaded

Example:

<mesh type="obj">
	<string name="filename" value="ext_ball.obj"/>
	<bsdf type="diffuse">
		<color name="albedo" value="0.5, 0.5, 0.5"/>
	</bsdf>
	<transform name="toWorld">
		<scale value="0.06,0.06,-1"/>
		<translate value="10,0,25"/>
	</transform>
</mesh>

Rectangle(`rectangle`)

A simple rectangular shape primitive.

Parameter	Type	Description
`pos`	vector	The corner point of the rectangle
`v0`	vector	An edge vector of the rectangle.
`v1`	vector	Another edge vector of the rectangle.

The light normal is normalize(cross(v0, v1))

<mesh type="rectangle">
	<vector name="pos" value="-1, -100, 99"/>
	<vector name="v0" value="2, 0, 0"/>
	<vector name="v1" value="0, 0, 2"/>
</mesh>

Emitters

Area Light(`area`)

Turn a geometric object into a area light source.

Parameter	Type	Description
radiance	color	Specifies the emitted radiance in units of power per unit area per unit steradian.

<shape type="obj">
    <emitter type="area">
        <color name="radiance" value="1.0 1.0 1.0"/>
    </emitter>
</shape>

Point Light (`point`)

A simple point light source, which uniformly radiates illumination into all directions.

Parameter	Type	Description
intensity	color	Specifies the emitted radiance in units of power per unit area per unit steradian.
position	point	light source position

<emitter type="area">
	<color name="intensity" value="3,3,2.5"/>
    <point name="position" value="0, 0, 0"/>
</emitter>

Environment Light(`envmap`)

An HDRI (high dynamic range imaging) environment map.

Parameter	Type	Description
`filename`	string	Filename of the radiance-valued input image to be loaded; must be in latitude-longitude format.
`scale`	float	Scale the intensity of envmap
`visual`	boolean	Whether to visualize the envmap

<emitter type="envmap">
	<string name="filename" value="envmap.hdr"/>
	<boolean name="visual" value="false"/>
	<float name="scale" value="0.5"/>
</emitter>

Textures

Texture objects can be attached to certain material to introduce spatial variation.

Bitmap texture(`bitmap`)

Parameter	Type	Description
`filename`	string	Filename of the bitmap to be loaded

Examples:

<texture type="bitmap">
	<string name="filename" value="vrata_kr.JPG"/>
</texture>

BSDFs

Diffuse(`diffuse`)

An ideally diffuse material, also referred to as Lambertian.

Parameter	Type	Description
`albedo`	color or texture	Specifies the diffuse albedo of the material (Default: 0.5)

Example:

<bsdf type="diffuse">
	<color name="albedo" value="0.5,0.5,0.5"/>
</bsdf>

or textured albedo:

<bsdf type="diffuse">
	<texture type="bitmap">
		<string name="filename" value="wood.jpg"/>
	</texture>
</bsdf>

Dielectric(`dielectric`)

The material models the reflection and refraction between two dielectric materials having mismatched indices of refraction (for instance, water ↔ air)

Parameter	Type	Description
`intIOR`	float	Interior index of refraction specified numerically(Default: 1.5046)
`extIOR`	float	Exterior index of refraction specified numerically("exterior" refers to the side that contains the surface normal)(Default: 1.000277)

<bsdf type="dielectric"/>

Mirror(`mirror`)

An ideal mirror.

<bsdf type="mirror"/>

Microfacet(`microfacet`)

Diffuse brdf + rough conductor brdf.

The microfacet normal distribution is beckmann distribution.

Parameter	Type	Description
`intIOR`	float	Interior index of refraction specified numerically(Default: 1.5046)
`extIOR`	float	Exterior index of refraction specified numerically("exterior" refers to the side that contains the surface normal)(Default: 1.000277)
`alpha`	float	Surface roughness
`kd`	color	Albedo of the diffuse base material

Example:

<bsdf type="microfacet">
	<float name="intIOR" value="1.7"/>
	<color name="kd" value="0.2 0.2 0.4"/>
	<float name="alpha" value="0.28"/>
</bsdf>

Anisotropic GGX(`aniso_ggx`)

Diffuse brdf + anisotropic ggx brdf

The microfacet normal distribution is GGX distribution.

Parameter	Type	Description
`pd`	color or texture	diffuse albedo
`ps`	color or texture	specular albedo
`axay`	color or texture	surface roughness

Optional parameters:

Parameter	Type	Description
`normal`	texture	normal texture
`tangent`	texture	tangent texture
`is_tangent_space`	boolean	Whether the normal/tangent texture is in tangent space or not(default true).

Examples:

<bsdf type="aniso_ggx">
	<boolean name="is_tangent_space" value="true"/>
	<color name="pd" value="0., 0., 0."/>
	<color name="ps" value="0.5, 0.5, 0.5"/>
	<color name="axay" value="0.2, 0.2, 1."/>
</bsdf>

<bsdf type="aniso_ggx">
	<boolean name="is_tangent_space" value="false"/>
	<texture type="bitmap" name="pd">
		<string name="filename" value="pd_texture.exr"/>
	</texture>
	<texture type="bitmap" name="ps">
		<string name="filename" value="ps_texture.exr"/>
	</texture>
	<texture type="bitmap" name="axay">
		<string name="filename" value="ax_ay_texture.exr"/>
	</texture>
	<texture type="bitmap" name="normal">
		<string name="filename" value="normal_texture.exr"/>
	</texture>
	<texture type="bitmap" name="tangent">
		<string name="filename" value="tangent_texture.exr"/>
	</texture>
</bsdf>

Declare and References

If one material or texture will be used many times, you can declare the material/texture forward, and reference it in many places.

For examples:

<scene>
	<bsdf type="diffuse" id="test_mat">
		<color name="albedo" value="0.5, 0.5, 0.5"/>
	</bsdf>
	<mesh type="obj">
		<ref id="test_mat">
	</mesh>
</scene>

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Documentation

Usage

Scene XML file format

Properties

Transform

Integrators

Path Tracer(`path`)

Normal(`normals`)

Samplers

Independent sampler(`independent`)

Cameras

Perspective camera(`virtual`)

OpenCV camera(`opencv`)

Meshes

Wavefront OBJ mesh(`obj`)

Rectangle(`rectangle`)

Emitters

Area Light(`area`)

Point Light (`point`)

Environment Light(`envmap`)

Textures

Bitmap texture(`bitmap`)

BSDFs

Diffuse(`diffuse`)

Dielectric(`dielectric`)

Mirror(`mirror`)

Microfacet(`microfacet`)

Anisotropic GGX(`aniso_ggx`)

Declare and References

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DOCUMENTATION.md

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DOCUMENTATION.md

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Documentation

Usage

Scene XML file format

Properties

Transform

Integrators

Path Tracer(path)

Normal(normals)

Samplers

Independent sampler(independent)

Cameras

Perspective camera(virtual)

OpenCV camera(opencv)

Meshes

Wavefront OBJ mesh(obj)

Rectangle(rectangle)

Emitters

Area Light(area)

Point Light (point)

Environment Light(envmap)

Textures

Bitmap texture(bitmap)

BSDFs

Diffuse(diffuse)

Dielectric(dielectric)

Mirror(mirror)

Microfacet(microfacet)

Anisotropic GGX(aniso_ggx)

Declare and References

Path Tracer(`path`)

Normal(`normals`)

Independent sampler(`independent`)

Perspective camera(`virtual`)

OpenCV camera(`opencv`)

Wavefront OBJ mesh(`obj`)

Rectangle(`rectangle`)

Area Light(`area`)

Point Light (`point`)

Environment Light(`envmap`)

Bitmap texture(`bitmap`)

Diffuse(`diffuse`)

Dielectric(`dielectric`)

Mirror(`mirror`)

Microfacet(`microfacet`)

Anisotropic GGX(`aniso_ggx`)