Icon Quaternion Weighted Average


Icon BVHView


Icon Dead Blending Node in Unreal Engine


Icon Propagating Velocities through Animation Systems


Icon Cubic Interpolation of Quaternions


Icon Dead Blending


Icon Perfect Tracking with Springs


Icon Creating Looping Animations from Motion Capture


Icon My Favourite Things


Icon Inertialization Transition Cost


Icon Scalar Velocity


Icon Tags, Ranges and Masks


Icon Fitting Code Driven Displacement


Icon atoi and Trillions of Whales


Icon SuperTrack: Motion Tracking for Physically Simulated Characters using Supervised Learning


Icon Joint Limits


Icon Code vs Data Driven Displacement


Icon Exponential Map, Angle Axis, and Angular Velocity


Icon Encoding Events for Neural Networks


Icon Visualizing Rotation Spaces


Icon Spring-It-On: The Game Developer's Spring-Roll-Call


Icon Interviewing Advice from the Other Side of the Table


Icon Saguaro


Icon Learned Motion Matching


Icon Why Can't I Reproduce Their Results?


Icon Latinendian vs Arabendian


Icon Machine Learning, Kolmogorov Complexity, and Squishy Bunnies


Icon Subspace Neural Physics: Fast Data-Driven Interactive Simulation


Icon Software for Rent


Icon Naraleian Caterpillars


Icon The Scientific Method is a Virus


Icon Local Minima, Saddle Points, and Plateaus


Icon Robust Solving of Optical Motion Capture Data by Denoising


Icon Simple Concurrency in Python


Icon The Software Thief


Icon ASCII : A Love Letter


Icon My Neural Network isn't working! What should I do?


Icon Phase-Functioned Neural Networks for Character Control


Icon 17 Line Markov Chain


Icon 14 Character Random Number Generator


Icon Simple Two Joint IK


Icon Generating Icons with Pixel Sorting


Icon Neural Network Ambient Occlusion


Icon Three Short Stories about the East Coast Main Line


Icon The New Alphabet


Icon "The Color Munifni Exists"


Icon A Deep Learning Framework For Character Motion Synthesis and Editing


Icon The Halting Problem and The Moral Arbitrator


Icon The Witness


Icon Four Seasons Crisp Omelette


Icon At the Bottom of the Elevator


Icon Tracing Functions in Python


Icon Still Things and Moving Things


Icon water.cpp


Icon Making Poetry in Piet


Icon Learning Motion Manifolds with Convolutional Autoencoders


Icon Learning an Inverse Rig Mapping for Character Animation


Icon Infinity Doesn't Exist


Icon Polyconf


Icon Raleigh


Icon The Skagerrak


Icon Printing a Stack Trace with MinGW


Icon The Border Pines


Icon You could have invented Parser Combinators


Icon Ready for the Fight


Icon Earthbound


Icon Turing Drawings


Icon Lost Child Announcement


Icon Shelter


Icon Data Science, how hard can it be?


Icon Denki Furo


Icon In Defence of the Unitype


Icon Maya Velocity Node


Icon Sandy Denny


Icon What type of Machine is the C Preprocessor?


Icon Which AI is more human?


Icon Gone Home


Icon Thoughts on Japan


Icon Can Computers Think?


Icon Counting Sheep & Infinity


Icon How Nature Builds Computers


Icon Painkillers


Icon Correct Box Sphere Intersection


Icon Avoiding Shader Conditionals


Icon Writing Portable OpenGL


Icon The Only Cable Car in Ireland


Icon Is the C Preprocessor Turing Complete?


Icon The aesthetics of code


Icon Issues with SDL on iOS and Android


Icon How I learned to stop worrying and love statistics


Icon PyMark


Icon AutoC Tools


Icon Scripting xNormal with Python


Icon Six Myths About Ray Tracing


Icon The Web Giants Will Fall


Icon PyAutoC


Icon The Pirate Song


Icon Dear Esther


Icon Unsharp Anti Aliasing


Icon The First Boy


Icon Parallel programming isn't hard, optimisation is.


Icon Skyrim


Icon Recognizing a language is solving a problem


Icon Could an animal learn to program?




Icon Pure Depth SSAO


Icon Synchronized in Python


Icon 3d Printing


Icon Real Time Graphics is Virtual Reality


Icon Painting Style Renderer


Icon A very hard problem


Icon Indie Development vs Modding


Icon Corange


Icon 3ds Max PLY Exporter


Icon A Case for the Technical Artist


Icon Enums


Icon Scorpions have won evolution


Icon Dirt and Ashes


Icon Lazy Python


Icon Subdivision Modelling


Icon The Owl


Icon Mouse Traps


Icon Updated Art Reel


Icon Tech Reel


Icon Graphics Aren't the Enemy


Icon On Being A Games Artist


Icon The Bluebird


Icon Everything2


Icon Duck Engine


Icon Boarding Preview


Icon Sailing Preview


Icon Exodus Village Flyover


Icon Art Reel




Icon One Cat Just Leads To Another

Painting Style Renderer

Created on July 4, 2011, 1:03 p.m.

I've always loved photorealism in graphics but I do get the sense that people are too unwilling to experiment with it. Often a "realistic" renderer means that the art team stops bothering with anything interesting in the artistic direction. Perhaps that is unfair - but at the very least it gives them the excuse to fall back into the artistic cliches which we all love - gritty realism, bright fantasy and greeble infested sci-fi.

Because of this, non-photo-realism has always had a nagging at the back of my head, so I decided to try and roll a renderer that did something a bit different. This is what I've come up with so far:



The main inspiration comes from a couple of papers and presentations. The best paper I found is one by Barbara J. Meier from 1996 which suggests an offline rendering algorithm for a painterly style. There is also a later paper by a German Student Daniel Sperl who suggests a possible implementation in OpenGL using similar techniques. Worth mentioning, but not something I used is another presentation which looked like it presented a very cheap effect but I wasn't happy with the resulting look.

The basic idea is this: generate thousands of particles at different positions on a mesh and render these as "brush strokes" in screen space. This gives a painting style effect without much of the randomness or changes/flickering which you get in other post effects and can be off-putting.

To know the color of these brush strokes you first render the scene as usual and then use this reference image for a color lookup.

The offline technique presented by Barbara is done on the CPU and there were certain things I could not emulate in the graphics pipeline, but none were that important. For several of these I came up with solutions which I think work better anyhow.

The implementation proposed by Daniel Sperl was also interesting but lacked some of the features from the offline version such as orientation of particles, which I added. I also changed around how the billboarded particles are rendered to a far cheaper technique and moved the data into a VBO which sped draw times up significantly.

After much testing it became apparent that the bottleneck in the system is not actually the number of particles. It is the fill time of the particles, mainly due to the fact they are alpha blended onto the scene. I could easily render several million particles when they only covered a couple pixels each, but when their size grew, and they began to overlap each other, that is when the slowdown really begun. The problem was, without fairly large overlapping particles it is almost impossible to avoid gaps inbetween the strokes where the background shows through.

My first attempt at a solution was to do something normal painters do, I rendered a base layer with much larger and fewer particles to fill the gaps. Unfortunately there were two issues with this. First of all it was expensive - as the fill time was just as high as rendering lots of particles. Secondly it completely messed up the silhouette of objects as the brush strokes were so large.

On my second attempt I drew the reference image (of the normally rendered scene) below the particles. This filled in any gaps, but the silhouette was still bad. In some places it had a per-pixel sharpness and in others it was blurred where a brush stroke went across it.

In the end I think I came up with quite a novel solution, which is to render the reference image at a quarter of the screen size. This avoids having a sharp silhouette and fills in the gaps much more seamlessly. The added advantage is that the first pass, in drawing the scene as usual, becomes quite a bit faster. In fact, this pattern of taking advantage of the intrinsic loss of detail due to the effect, seems to be the key to getting the most out of the renderer. As well as downscaling the reference image it also makes sense to drop normal maps and texture resolutions, and any of the unneeded detail which wont be seen in the final product. Hopefully this makes up somewhat for the memory sucking horror of generating hundreds of thousands of particles per mesh.

For rendering the particles it made sense to have a LOD system. In the end I generated a set of Element Index Buffers for each object which skipped out every other or every third (etc) particle and used different ones of these based on distance.

There were some other tricks to reduce the fill time time too. The surface normal was stored with each particle and it's angle to the screen calculated in the vertex shader. This allowed me to shrink particles at a sharp angle to the screen and cull ones which were backfacing. The depth is rendered to texture when rendering the reference image and this can be used as a kind of poor man's depth sorting. You can discard particle fragments which are behind the reference object.

Currently the orientation is based upon either the tangent or binormal vector depending on the size of each UV triangle, but it is perfectly possible to allow the artist full control via either all strokes align along the UV x-axis or the UV y-axis. Stroke orientation and size is something I really want to experiment with in future as currently it has a very Monet type feel due to the small strokes.

The other thing that needs work is the colors. I feel there needs to be some post effect, perhaps increasing contrast and saturation. The shadows also seems to be off. This could be due to the color as I feel they need to be more blue and the light more orange. These are things which can all come down to tweaking though.

Anyway, I'm very welcome to ideas suggestions and feedback. In honesty I've been starting at that piano so long I hardly know what looks good any more.

github twitter rss