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Ray tracing engine (Python)
msyvr/raytracer
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Python ray tracing engine
- Render a 3D scene by simulating its illumination
- For each output image pixel, in-scene optical interactions are computed to determine the color of the pixel’s incoming light ray
- NB: computationally intensive
- this implementation is not performance optimized via parallelization, bounding volumes, etc.
- run time depends on image size and recursion depth
- Output/image file: raytray.png
- Run time:
- scales with ‘display_scale’ and recursion ‘depth’ parameters:
- display size (default): [16:9] scaled by display_scale
- run time scales with number of pixels: display_scale**2
Image saved as raytray_image.png Display: 800 x 450 Time to compute: 536.0476911067963 s- Python modules (all imported in main.py):
- math
- numpy
- matplotlib
- time (optional)
Python ray tracer: example image series
This sequence of images demonstrates the evolution of a ray traced image with incremental additions of different optical contributions: ambient, diffuse surface scattering, shadows/occlusion, recursively traced reflection/refraction.
- An improved illumination model for shaded display (Whitted)
- Computer Graphics from Scratch — Ray Tracing Overview (scratchapixel)
- Nvidia has some great tech and resources for real time image generation incorporating ray tracing: Intro to NVIDIA RTX and DirectX ray tracing tech
- Radiance Caching for Real-Time Global Illumination: Daniel Wright (Engineering Fellow in graphics at Epic Games) at SIGGRAPH 2021
- A 3D scene volume is rendered to a 2D display based on physics-based in-scene optical interactions
- map* each 2D display position (pixel) to the nearest in-scene hit point
- starting from the hit point, recursively ray-trace reflection and refraction rays that contribute to the hit point color value:
- using the Fresnel equations, compute reflected and refracted rays from the hit point
- follow these two rays, recursively generating new reflection and refraction rays at each subsequent scene element intersection, until a ray intersects a light source (or the computation times out)
Ambient Light ||||||||||||||||||||||||||||||||||||||| ||||||||||||||||||||||||||||||||||||||| ==== Display Plane ==== |\ _____ ==== | \ / \ Scene ==== | \ / \ Objects ==== Camera | \ ( ) ==== | | \ \ / ______ ==== O)- - - - - |- > \ - - - *\ / ( ) ==== | \ | --- ( ) ==== \ | ( ) ==== \ | -- ==== \ | ==== \| ==== *** Scene *** Light- map 3D -> 2D:
- parametrize ray as a line between a virtual camera/eye (at an observer position, in front of the display) and the scene pixel:
- Point-on-ray-trajectory = ray.origin + t * ray.direction
- Not intended for production use
- !not! performance optimized: ray tracing is computationally expensive and this implementation is slow
for j in range(display_height): yd = yd_from_j(j, display_height, display_width) for i in range(display_width): xd = xd_from_i(i, display_width) pixel_ray = Ray(c.center, [xd, yd, zd]) t, hit_point, hit_element = find_nearest(pixel_ray, scene + lights) if hit_element != 0: c_ambient = ambient_contrib(hit_element) c_diffuse = diffuse_contrib(hit_point, hit_element) c_fresnel = fresnel_contrib(t, hit_point, pixel_ray.direction, hit_element, recursion_depth) color_xy = c_ambient + c_diffuse + c_fresnel else: color_xy = background_color img[j, i, :] = color_xy- Diffuse surface scattered (Lambertian) and indirect/recursive (Fresnel) contributions are physics-based
- NB: light information is carried by photons and the ray approximation in ray tracing is a design choice, trading off render precision for reduced computational expense
- The number and arrangement of display plane pixels is:
- n_vertical_pixels * n_horizontal_pixels
- Scene elements represented by classes
- Create the scene by generating class instances, specifying attributes: e.g., position, surface normal, color, Fresnel coefficients (reflectivity, index of refraction)
- With matplotlib, a .png file is generated via imsave().
- If no matplotlib, can write to .ppm file, formatted as:
- P3 (width: int) (height: int) ‘r’ ‘g’ ‘b’ ‘r’ ‘g’ ‘b’ . ‘r’ ‘g’ ‘b’ \n
- for .ppm files, ‘r’ ‘g’ ‘b’ are each in (usually) range(256) (and maximally limited to range(2^16))
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General 3-Dimensional Physics Engine in Python
Nick-Hemenway/simEngine3D
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simengine3D is a general purpose 3-dimensional physics simulation engine written entirely in python. I created it in grad school while taking «ME 751: Advanced Computational Multibody Dynamics.» Instead of deriving the governing differential equations of a system by hand, simengine3D allows a user to compose an arbitrary mechanical system in 3D space by defining rigid bodies (inerital properties and dimensions), and joints that connect bodies (ball joints, pin joints, etc.). The user can then apply external loads to the system (springs, dampers, control actuators) and simulate the time evolution of the system (recording reaction torques/forces and system kinematics along the way)
At the end of the course, Dr. Dan Negrut (the professor for the class) had this to say about the code:
To install, fork this repository and then clone it locally to your machine. Then:
- (Optional) Create a virtual environment before installing using your tool of choice
- Navigate terminal to folder containing pyproject.toml file and then:
- For general usage: pip install .
- If you wish to edit source code: pip install -e .
You will almost always start using simengine3D by creating a a System object. After instantiating a System , you can begin to add RigidBody objects to the system and then define joints between the bodies. The easiest way to get started with simengine3D is to look at the examples in the examples folder.
A combination of CamelCase and underscore notation is used throughout the code.
CamelCase is used for class names only.
Underscores are used for methods and attributes.
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General 3-Dimensional Physics Engine in Python
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(incomplete) Combines ModernGL with 3D rigid bodies and detection from PyBullet.
johnmwalker/Basic-3D-Physics-Engine-in-Python
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Basic 3D Physics Engine in Python
This is an evolution of my 2D Python Physics Game which I developed to gain some insight on the feasibility of guiding students to build such a physics engine for future offerings of PHYS 398 at the University of St. Thomas in St. Paul, MN.
My personal goal with this project was to learn about the basics of making a true physics engine while also keeping things as efficient and entertaining as possible. Hence I resorted to PyBullet for collision detection as I failed to find any resources to guide me explicitly through efficient detection and sorting algorithms.
Select your level (in App.py) and run the App.py file.
Note that levels 1-5 are holdovers from previous versions and do not currently work. 6-11 are functional.
- Collisions are awkward. Some look totally fine while others clearly don’t behave like they should.
- Normal forces and non-penetration constraints are not currently working, so things will gradually phase into each other.
About
(incomplete) Combines ModernGL with 3D rigid bodies and detection from PyBullet.
- P3 (width: int) (height: int) ‘r’ ‘g’ ‘b’ ‘r’ ‘g’ ‘b’ . ‘r’ ‘g’ ‘b’ \n
- parametrize ray as a line between a virtual camera/eye (at an observer position, in front of the display) and the scene pixel:
- display size (default): [16:9] scaled by display_scale
- scales with ‘display_scale’ and recursion ‘depth’ parameters:
