A path tracer written in Go.

Related tags

Images tools pt
Overview

pt: a golang path tracer

Build Status GoDoc

This is a CPU-only, unidirectional path tracing engine written in Go. It has lots of features and a simple API.

Examples


Features

  • Supports OBJ and STL
  • Supports textures, bump maps and normal maps
  • Supports raymarching of signed distance fields
  • Supports volume rendering from image slices
  • Supports various material properties
  • Supports configurable depth of field
  • Supports iterative rendering
  • Supports adaptive sampling and firefly reduction
  • Uses k-d trees to accelerate ray intersection tests
  • Uses all CPU cores in parallel
  • 100% pure Go with no dependencies besides the standard library

Installation

go get -u github.com/fogleman/pt/pt

Examples

The are lots of examples to learn from! To try them, just run, e.g.

cd go/src/github.com/fogleman/pt
go run examples/gopher.go

Optional Embree Acceleration

You can optionally utilize Intel's Embree ray tracing kernels to accelerate triangle mesh intersections. First, install embree on your system: http://embree.github.io/ Then get the go-embree wrapper and checkout the embree branch of pt.

git checkout embree
go get -u github.com/fogleman/go-embree

Hello World

The following code demonstrates the basics of the API.

package main

import . "github.com/fogleman/pt/pt"

func main() {
	// create a scene
	scene := Scene{}

	// create a material
	material := DiffuseMaterial(White)

	// add the floor (a plane)
	plane := NewPlane(V(0, 0, 0), V(0, 0, 1), material)
	scene.Add(plane)

	// add the ball (a sphere)
	sphere := NewSphere(V(0, 0, 1), 1, material)
	scene.Add(sphere)

	// add a spherical light source
	light := NewSphere(V(0, 0, 5), 1, LightMaterial(White, 8))
	scene.Add(light)

	// position the camera
	camera := LookAt(V(3, 3, 3), V(0, 0, 0.5), V(0, 0, 1), 50)

	// render the scene with progressive refinement
	sampler := NewSampler(4, 4)
	renderer := NewRenderer(&scene, &camera, sampler, 960, 540)
	renderer.AdaptiveSamples = 128
	renderer.IterativeRender("out%03d.png", 1000)
}

Hello World

Adaptive Sampling

There are several sampling options that can reduce the amount of time needed to converge to an acceptable noise level. Both images below were rendered in 60 seconds. On the left, no advanced features were enabled. On the right, the features listed below were used.

Gopher

Here are some of the options that are utilized to achieve this improvement:

  • stratified sampling - on first intersection, spawn NxN rays in a stratified pattern to ensure well-distributed coverage
  • sample all lights - at each intersection, sample all lights for direct lighting instead of one random light
  • forced specular reflections - at each intersection, force both a diffuse and specular bounce and weigh them appropriately
  • adaptive sampling - spend more time sampling pixels with high variance
  • firefly reduction - very heavily sample pixels with very high variance

Combining these features results in cleaner, faster renders. The specific parameters that should be used depend greatly on the scene being rendered.

Links

Here are some resources that I have found useful.

Samples

Go

Dragon

Cornell

Lucy

SDF

Spheres

Suzanne

Molecule

Comments
  • Is pt suitable for simple real-time rendering? Can this be implemented?

    Is pt suitable for simple real-time rendering? Can this be implemented?

    It would be great to have a simple real time rendering method on the CPU in pure Go that could be used to preview a model before rendering, is this feasible? When I say real time I mean rendering to a image type in a decent fraction of a second.

    opened by Splizard 10
  • Will OpenGL version of this PT?

    Will OpenGL version of this PT?

    Hello. Will you development OpenGL (or Vulkan) version of this good PT? I tried to build octree with hardware rasterization (and atomics), and acheive not so bad speed (interactive) with 20k polygons. Even If rebuild octree. Tested only for Nvidia, but now I have option for non-conservative (and slower) method of voxelization. https://github.com/acterhd/ogl-reflections

    opened by acterhd 3
  • Stopped ignoring errors

    Stopped ignoring errors

    Added error handling when reading files that are not there.

    Accept or reject at will (or ask me to change the pull request).

    Best regards, Alexander F Rødseth

    opened by xyproto 2
  • Submit gopher rendering to golang-graphics repository

    Submit gopher rendering to golang-graphics repository

    Would you be alright with me submitting your rendered gopher as a PNG to the golang-graphics repository? Of course you'd be duly credited and the original .obj file would be referenced as well (which I also would like to add to the repo).

    opened by mholt 2
  • cornell works, but...

    cornell works, but...

    Hi,

    When trying the examples, the cornell box works fine:

    ...t/pt/examples% ./cornell 
    Building k-d tree (8 shapes)... OK
    
    [Iteration 1 of 10]
    512 x 512 pixels, 1 x 16 = 16 samples, 4 bounces, 2 cores
      44 / 512 (  8%) [===                               ] 0:00:02 1.0M ^C%                                                                                                                                                                        
    

    However, the cube fails:

    ...t/pt/examples% ./cube 
    Loading STL (Binary): examples/cube.stl
    panic: runtime error: invalid memory address or nil pointer dereference
    [signal 0xb code=0x1 addr=0x0 pc=0x44183c]
    
    goroutine 1 [running]:
    github.com/fogleman/pt/pt.(*Mesh).FitInside(0x0, 0x0, 0x0, 0x0, 0x3ff0000000000000, 0x3ff0000000000000, 0x3ff0000000000000, 0x3fe0000000000000, 0x3fe0000000000000, 0x3fe0000000000000)
        /home/alexander/go/src/github.com/fogleman/pt/pt/mesh.go:105 +0x82c
    main.createMesh(0x3fa473f4a209de04, 0x3fb943b1fbe850e5, 0x3fc28e725522c76e, 0x0, 0x0, 0x0, 0x3ff0000000000000, 0x0, 0x0, 0x3ff8000000000000, ...)
        /home/alexander/checkout/pt/examples/cube.go:11 +0x16c
    main.main()
        /home/alexander/checkout/pt/examples/cube.go:18 +0x18e
    
    goroutine 2 [runnable]:
    runtime.forcegchelper()
        /usr/lib/go/src/runtime/proc.go:90
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    
    goroutine 3 [runnable]:
    runtime.bgsweep()
        /usr/lib/go/src/runtime/mgc0.go:82
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    
    goroutine 4 [runnable]:
    runtime.runfinq()
        /usr/lib/go/src/runtime/malloc.go:712
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    

    So does the gopher:

    2...t/pt/examples% ./gopher
    Loading OBJ: examples/gopher.obj
    panic: runtime error: invalid memory address or nil pointer dereference
    [signal 0xb code=0x1 addr=0x0 pc=0x43fb9b]
    
    goroutine 1 [running]:
    github.com/fogleman/pt/pt.(*Mesh).SmoothNormals(0x0)
        /home/alexander/go/src/github.com/fogleman/pt/pt/mesh.go:84 +0x98b
    main.main()
        /home/alexander/checkout/pt/examples/gopher.go:13 +0xa4e
    
    goroutine 2 [runnable]:
    runtime.forcegchelper()
        /usr/lib/go/src/runtime/proc.go:90
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    
    goroutine 3 [runnable]:
    runtime.bgsweep()
        /usr/lib/go/src/runtime/mgc0.go:82
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    
    goroutine 4 [runnable]:
    runtime.runfinq()
        /usr/lib/go/src/runtime/malloc.go:712
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    

    And the cylinder:

    ...t/pt/examples% ./cylinder 
    Loading STL (Binary): examples/cylinder.stl
    panic: runtime error: invalid memory address or nil pointer dereference
    [signal 0xb code=0x1 addr=0x0 pc=0x44018c]
    
    goroutine 1 [running]:
    github.com/fogleman/pt/pt.(*Mesh).FitInside(0x0, 0xbfb999999999999a, 0xbfb999999999999a, 0x0, 0x3ff199999999999a, 0x3ff199999999999a, 0x4059000000000000, 0x3fe0000000000000, 0x3fe0000000000000, 0x0)
        /home/alexander/go/src/github.com/fogleman/pt/pt/mesh.go:105 +0x82c
    main.createMesh(0x3fc633401672b92a, 0x0, 0x3fadcab5b09790d5, 0x0, 0x0, 0x0, 0x3ff0000000000000, 0x0, 0x0, 0x3ff999999999999a, ...)
        /home/alexander/checkout/pt/examples/cylinder.go:7 +0x16c
    main.main()
        /home/alexander/checkout/pt/examples/cylinder.go:15 +0x18e
    
    goroutine 2 [runnable]:
    runtime.forcegchelper()
        /usr/lib/go/src/runtime/proc.go:90
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    
    goroutine 3 [runnable]:
    runtime.bgsweep()
        /usr/lib/go/src/runtime/mgc0.go:82
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    
    goroutine 4 [runnable]:
    runtime.runfinq()
        /usr/lib/go/src/runtime/malloc.go:712
    runtime.goexit()
        /usr/lib/go/src/runtime/asm_amd64.s:2232 +0x1
    

    This is on 64-bit Arch Linux, kernel 3.18.6, go 1.4.1.

    Wonderful project, btw!

    Best regards, Alexander F Rødseth

    opened by xyproto 1
  • Would you consider a rename?

    Would you consider a rename?

    "pt" conflicts with this: https://github.com/monochromegane/the_platinum_searcher which is a fast replacement for "ack". Would you entertain renaming your path tracer? How about "ptr"? If not, no biggie... feel free to close this "issue". :-) Awesome job, by the way! I can't wait to try it out!!!

    opened by gmlewis 1
  • Fix compilation of suzanne.go

    Fix compilation of suzanne.go

    Unfortunately, running the program still results in an error: Loading examples/suzanne.obj... OK 2015/02/06 20:42:00 LoadOBJ error: open examples/untitled.mtl: no such file or directory

    Change-Id: Ife9ebce15adfd8db5d5d23ce52520818e48c339d

    opened by gmlewis 0
  • Add https://travis-ci.org to keep track of build status.

    Add https://travis-ci.org to keep track of build status.

    Hi Michael,

    Here is a suggestion to add Travis CI to automatically build each github push so you can see if everything is still working properly. You can see this in-action here: https://github.com/gmlewis/pt/tree/add-travis and note the the build is currently failing. You can get the details by clicking on the "failing" link and then click on either 7.1 (Go 1.4.1) or 7.2 (tip): https://travis-ci.org/gmlewis/pt/jobs/49826626

    You can create your own free Travis CI account and then change the "gmlewis" to "fogleman" and it will track your original repository instead of my fork.

    I'm really looking forward to playing with this... thanks so much for writing it!

    -- Glenn

    opened by gmlewis 0
  • Any pointers for docs?

    Any pointers for docs?

    This seems like a very cool project, thanks. As someone incredibly new to the domain, I was trying to play with the examples but it is very exhausting to play around without any documentation or comments in the code. I checked the source code as well, but couldn't see any comments around the variables and functions. Is there any documentation that I might have missed regarding how to use this project?

    I can play around with all the variables and probably figure out how most of them work, but I was hoping to use this to inspire my brother with ray tracing, and I am afraid this might demotivate it, so if someone can point me to a simple documentation that'd be awesome.

    Cheers!

    opened by karakanb 0
  • SDFShape support for ClearMaterial

    SDFShape support for ClearMaterial

    I tried to add a SphereSDF to the materials example, on the far right, using the same ClearMaterial as the regular Sphere next to it, but the result looks metallic.

    Curious to know:

    • Is transparency expected to work with SDF shapes?
    • If so, any pointers on how I can go about fixing this? My first guess is something to do with Hitinfo at https://github.com/fogleman/pt/blob/master/pt/hit.go#L37, but it seems best to ask for ideas before going down the rabbit hole :-)

    out100

    package main
    
    import . "github.com/fogleman/pt/pt"
    
    func main() {
    	scene := Scene{}
    	r := 0.4
    	var material Material
    
    	material = DiffuseMaterial(HexColor(0x334D5C))
    	scene.Add(NewSphere(V(-2, r, 0), r, material))
    
    	material = SpecularMaterial(HexColor(0x334D5C), 2)
    	scene.Add(NewSphere(V(-1, r, 0), r, material))
    
    	material = GlossyMaterial(HexColor(0x334D5C), 2, Radians(50))
    	scene.Add(NewSphere(V(0, r, 0), r, material))
    
    	material = TransparentMaterial(HexColor(0x334D5C), 2, Radians(20), 1)
    	scene.Add(NewSphere(V(1, r, 0), r, material))
    
    	material = ClearMaterial(2, 0)
    	scene.Add(NewSphere(V(2, r, 0), r, material))
    	// Added SphereSDF
    	scene.Add(NewSDFShape(NewTransformSDF(NewSphereSDF(r), Translate(V(3, r, 0))), material))
    
    	material = MetallicMaterial(HexColor(0xFFFFFF), 0, 1)
    	scene.Add(NewSphere(V(0, 1.5, -4), 1.5, material))
    
    	scene.Add(NewCube(V(-1000, -1, -1000), V(1000, 0, 1000), GlossyMaterial(HexColor(0xFFFFFF), 1.4, Radians(20))))
    	scene.Add(NewSphere(V(0, 5, 0), 1, LightMaterial(White, 25)))
    	camera := LookAt(V(0, 3, 7), V(0, 1, 0), V(0, 1, 0), 30)
    	sampler := NewSampler(16, 16)
    	renderer := NewRenderer(&scene, &camera, sampler, 960, 540)
    	renderer.IterativeRender("out%03d.png", 100)
    }
    
    opened by seanpringle 1
  • Efficiency of Marching Cubes.

    Efficiency of Marching Cubes.

    For each cube you do an evaluation on the 8 vertices of the cube. Cubes are adjacent so many vertices will get evaluated up to 8 times - to produce the same result each time. I borrowed your code for my project and improved it by evaluating and caching 2D layers. It's a nice speed up if you care about STL generation (which I do). https://github.com/deadsy/sdfx/blob/master/sdf/marching.go Thanks for the code!

    opened by deadsy 3
  • Scene.RayCount crashes on 32bit systems with cgo

    Scene.RayCount crashes on 32bit systems with cgo

    Hey

    First thank you for this lib and also for your other lib ln :) I had great fun playing around with the examples and even build an example on top of your examples for my lib here: https://github.com/therecipe/qt/tree/master/internal/examples/widgets/renderer

    But it seems like the examples crash if you compile them for windows/386 in combination with cgo. I tracked the problem down and wrote some about it here: https://github.com/therecipe/qt/issues/125

    Basically to fix this you would just have to re-order this struct https://github.com/fogleman/pt/blob/master/pt/scene.go#L5-L13 and simply move rays to the top.

    I hoped that you would fix this, so that I don't have to send a PR for such a small change.

    opened by therecipe 0
Owner
Michael Fogleman
Software Engineer at Formlabs
Michael Fogleman
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