Category Archives: Tool

Talk at SIGGRAPH Asia 2018

We are proud to announce that we will be at the computer graphics conference SIGGRAPH Asia 2018 this December, where we will present the techniques used to create our 64K intro, H – Immersion.

At the conference, the “Computer Animation Festival” celebrates storytelling and animation in general, and showcases some of the best works of the year. We are honoured to have been selected among the talks there, and still in disbelief to be sitting next to talks about Pixar’s Incredibles 2 or Solo: A Star Wars Story.

If you are attending SIGGRAPH Asia this December in Tokyo, come to our session on Thursday 6th of December, from 16:15 to 18:00, in room G502 (glass building, fifth floor). All the details are available on the SIGGRAPH Asia 2018 session description. There is an iCalendar file as well.

A damaged mosaic texture

Texturing in a 64kB intro

This article is the second part of our series on the making of H – Immersion. You can read the first part here: A dive into the making of Immersion.

When making an animation within only 64kB, using images is tricky. We can’t store them in a traditional way, because it is not efficient enough, even with a compression like JPEG. An alternative solution is procedural generation. It consists in using code to describe how to create the images at runtime. Our implementation of such a solution is the texture generator, a core part of our toolchain. In this post we will present how we designed it and how we used it in H – Immersion.

Seafloor scene

The spotlights of a submersible reveal details of the seafloor.

Early version

Texture generation has been one of the earliest elements of our code base: our first intro, B – Incubation, already had procedural textures. The code consisted in a set of functions to fill, filter, transform and combine textures, and one big loop to go over all the textures. Those functions were written in plain C++, but were later exposed with a C API so they could be evaluated by a C interpreter, PicoC. At the time, we were using PicoC in an effort to reduce iteration time: in this case it allowed to modify and reload the textures at runtime. Limiting ourselves to the C subset was a small price to pay for the ability to change code and see the result without having to quit, compile and reload the entire demo again.

Steps for creating a wood texture

With a simple pattern, some noise and some deformation, we can obtain a stylized wood texture.

Desk scene

Various wood textures are used in this scene from F – Felix’s workshop.

We explored for a while what we could do with that generator, and ended up putting it on a web server with a small PHP script behind a simple web interface. We would write texture code in a text field, the script would feed it to the generator, which would then dump the result as a PNG file for the page to display. Soon enough, we found ourselves doodling from the office during lunch breaks and sharing our little creations among group members. This interaction was very motivating for creativity.

An online gallery of procedural textures

Our old texture generator web gallery. All the textures were editable in the browser.

A complete redesign

For a long time the texture generator almost didn’t change; we thought it was fine and our efficiency plateaued. Then we woke up one day, and discovered that Internet forums were suddenly full of artists showing off their 100% procedurally generated textures and challenging each other with themes. Procedural content used to be a demoscene thing, but Allegorithmic, ShaderToy and the likes had now made it accessible to the crowd while we had not been paying attention, and they were beating us hard. Unacceptable!

previous arrow
next arrow

It was long due time to reevaluate our tools. Fortunately working with the same texture generator for several years had given us time to understand its flaws. Our nascent mesh generator was also giving us some additional perspective on what we wanted a procedural content pipeline to look like.

The most important architecture mistake was the implementation of generation as a set of operations on textures objects. From a high level perspective, it may be a correct way of viewing it, but at the implementation level, having functions like texture.DoSomething() or Combine(textureA, textureB) has severe drawbacks.

First, the OOP style requires to declare those functions as part of the API, no matter how simple they are. This is a major problem because it doesn’t scale well and more importantly, it creates friction in the creation process. We don’t want to change the API every time we try something new. It makes experimentation more difficult, and ultimately limits artistic creativity.

Second, in terms of performance, it forces to loop over texture data as many times as there are operations. It wouldn’t matter too much if those operations were expensive relative to the cost of accessing large chunks of memory, however that’s usually not the case. Except for a few operations like generating a Perlin noise or doing a flood fill, most are in fact very simple and require few instructions per texture point. This means we keep traversing texture data to do trivial operations, which is ridiculously cache inefficient.

The new design addresses those issues with a simple reorganization of the logic. In practice, the majority of the functions just do the same operation for each element of the texture, independently. So instead of writing a function texture.DoSomething() which goes through all the elements, we can write texture.ApplyFunction(f) where f(element) only works on a single texture element. f(element) can then be written ad hoc for a specific texture.

This seems to be a minor modification. Yet doing so simplifies the API, makes the generation code more flexible and more expressive, is more cache friendly and trivially parallelizable. Many of you readers will probably recognize this as being essentially… a shader. Although the implementation is still, in fact, C++ code running on the CPU. We also keep the ability to do operations outside of the loop like before, but we only use that option when it is relevant, for example when doing a convolution.


// Logic is at the texture level.
// The API is bloated.
// The API is all there is.
// Generation of a texture has many passes.
class ProceduralTexture {
  void DoSomething(parameters) {
    for (int i = 0; i < size; ++i) {
      // Implementation details here.
      (*this)[i] = …
  void PerlinNoise(parameters) { … }
  void Voronoi(parameters) { … }
  void Filter(parameters) { … }
  void GenerateNormalMap() { … }

void GenerateSomeTexture(texture t) {
  … // etc.


// Logic is usually at the texture element level.
// The API is minimal.
// Operations are written as needed.
// Generation of a texture has a reduced number of passes.
class ProceduralTexture {
  void ApplyFunction(functionPointer f) {
    for (int i = 0; i < size; ++i) {
      // Implementation passed as a parameter.
      (*this)[i] = f((*this)[i]);

void GenerateNormalMap(ProceduralTexture t) { … }

void SomeTextureGenerationPass(void* out, PixelInfo in) {
  result = PerlinNoise(in);
  result = Filter(result);
  … // etc.
  *out = result;

void GenerateSomeTexture(texture t) {


Generating textures takes time, and an obvious candidate for reducing that time is to have parallel code execution. At the very least, it is possible to generate several textures concurrently. This is what we did up to F Felix’s workshop and it greatly reduced loading time.

However, doing so doesn’t shorten generation time where we most want it. Generating a single texture still takes as much time. That affects editing, when we keep reloading the same texture again and again between each modification. It is preferable to parallelize the inner texture generation code instead. Since the code now essentially consists in just one big function applied in a loop to each texel, parallelization becomes very simple and efficient. The cost of experimenting, tweaking and doodling is reduced, and that directly impacts creativity.

A damaged mosaic texture
A mosaic texture
previous arrow
next arrow

This illustration is an idea that we explored and abandoned for H – Immersion: a mosaic decoration with orichalcum lining. It is shown here in our live editing tool.

GPU side generation

In case it isn’t completely clear in the paragraphs above, texture generation is done entirely on the CPU. At this point some of you might be staring at these lines with incredulity and thinking: “But, why?!”. Generating textures on the GPU would seem like the obvious thing to do. For starters it would likely speed up generation by an order of magnitude. So, why?

The main reason is that it was a smaller step of redesign to stay on CPU. Moving to GPU would have been more work. It would have required to solve additional problems, new problems we don’t have enough experience with yet. On CPU we had a good understanding of what we wanted and how to fix some of the earlier mistakes.

The good news however, is that with the new design it now seems fairly trivial to experiment with GPU side generation as well. In the future, testing combinations of both could be an interesting path to explore.

Texture generation and physically based shading

Another limitation of the old design was that a texture was considered to be just an RGB image. If we wanted to generate more information, say, a diffuse texture and a normal texture for a same surface, nothing was preventing us from doing that, but the API wasn’t actively helping either. This takes special importance in the context of Physically Based Shading (PBR).

In a traditional non-PBR pipeline, surfaces typically use color textures in which a lot of information is baked. Those textures often represent the final appearance of the surface: they already have some volume, the crevices are darkened, and they may even have some reflection highlights. If more than one texture is used at a time, it’s usually to combine details of large and small scale, to add normal mapping, or to represent how reflective the surface is.

In a PBR pipeline on the contrary, surfaces tend to use sets of different textures that represent physical values rather than a desired artistic result. The diffuse color texture, which is the closest to what we commonly describe as “the color” of a surface, typically looks flat and uninteresting. The specular color is dictated by the surface index of refraction. Most of the detail and variety come from the normal and the roughness textures (which you could argue represent the same thing, but at two different scales). How reflective the surface feels just becomes a consequence of the roughness. At this point, it makes sense not to think in terms of textures anymore, but in terms of materials.

Greetings marble floor texture breakoff
Cobbles textures breakoff
Fountain scene
Seafloor textures breakoff
Seafloor scene
Old stone textures breakoff
Arch scene
Submersible body texture breakoff
Launch scene
previous arrow
next arrow

The current design allows to declare arbitrary pixel formats for textures. By making it part of the API, we can have all the boilerplate taken care of. Once the pixel format is declared, we can focus on writing the creative code, without spending additional effort on processing that data. Upon execution, it will generate several textures and upload them to the GPU, transparently.

Some PBR workflows don’t directly expose diffuse and specular colors, but instead a “base color” and a “metalness” parameter, which have some advantages and some disadvantages. In H – Immersion we use a diffuse+specular model, and a material usually consists of 5 layers:

  1. Diffuse color (RGB; 0: Vantablack; 1: fresh snow).
  2. Specular color (RGB: proportion of reflected light at 90°, aka. F0 or R0).
  3. Roughness (A; 0: perfectly smooth; 1: rubber like).
  4. Normal (XYZ; unit vector).
  5. Relief elevation (A; used for parallax occlusion mapping).

When it was used, emissive detail was added directly in the shader. It didn’t seem necessary to have ambient occlusion either since most scenes didn’t have ambient light at all. It wouldn’t be surprising to have such additional layers though, or other kind of information like anisotropy or opacity for example.

Wall texture without ambient occlusion
Wall texture with ambient occlusion
previous arrow
next arrow

Pictured here is a recent experiment at generating local ambient occlusion based on the height. For each direction, march a given distance and keep the biggest tangent (height difference divided by distance). Finally, compute occlusion from the average tangent.

Limitations and future work

As you can see, the current design is a strong improvement over the previous one, and it provides creative expressivity. However, it still has limitations that we would like to address in the future.

For example, although it wasn’t a problem for this intro, we noticed that memory allocation could be an obstacle. The generation of a texture uses a single array of floats. For large textures with many layers, this can quickly hit the point where allocation fails. There are various ways to address this, but they all come with drawbacks. For example we could generate the textures tile by tile, which would scale better, but some operations like convolution would become less straightforward to implement.

Finally in this article despite using the word “material”, we have only talked about textures and never about shaders. Yet a material should arguably encompass the shading part as well. This contradiction reflects the limitation of our current design: texture generation and shading are two distinct parts, separated by a bridge. We have tried to make that bridge as simple to cross as possible, but what we really want is to treat the two as a whole. For example, if a material has static features as well as dynamic ones, we want to describe them in a same place. This is a difficult topic and we don’t know yet what could be a good solution but, let’s go one step at a time.

A doodle after Imadol Delgado's texture

An experiment in trying to create a fabric texture similar to the earlier texture by Imadol Delgado.

Shader Minifier 1.1

I’ve just released Shader Minifier 1.1. You can download the binary at the usual place.


  • New output options: use --format js to generate a Javascript file, and --format c-array to get a comma-separated list of strings (to be included in a C array).
  • Use the new option --no-renaming-list if there are identifiers you don’t want to get renamed (e.g. entry point functions in HLSL)
  • If you have #define macros, Shader Minifier will now avoid conflicts between macros and identifier renaming.
  • If your code has conditions with compile-time known values, they will get simplified (e.g. if (false), or int i_tag = 2; if (i_tag < 4) ...).
  • If there are many identifiers in your code (this probably won’t happen in a 4k intro), Minifier will now use 2-letter names if needed. This is not correctly optimized, but some people use this tool for obfuscation, instead of size-optimization.
  • The option --preserve-all-globals won’t rename any global variable or any function. This is useful if your shader is split between multiple files.
  • You can now tell the Minifier not to parse some block of code. Put your code between //[ and //] and it won’t be parsed, identifiers won’t be renamed, but spaces and comments will still be removed. This is very useful if you want to use features not yet supported in the tool (e.g. forward declarations, or layouts).
  • Other fixes in the parser (macros can be used in a function block, numbers can have suffixes, etc.)
  • Unix support. Use this zip file instead of the standard release, install a recent version of Mono (at least 2.10) and run mono shader_minifier.exe. This should work.
  • Online Minifier. You can use shader minifier online, but only one shader at a time.

Who is using it?

During the last year, many great intros have used it with great success.

  • Another Theory, by FRequency (#1 at Main 2010)
  • white one by Never (#1 at the Ultimate Meeting 2010)
  • anglerfish by Cubicle (#1 at Assembly 2011)
  • RED by BluFlame (#1 at Evoke 2011)
  • akiko by flopi (#2 at Riverwash 2011)
  • fr-071: sunr4y by farbrausch (#1 at Sunrise 2011)

Shader Minifier 1.0

Since last release, the number of users of GLSL Minifier has increased, while number of bug reports decreased. I think it’s a good reason to move to version 1.0. This obfuscator has been used in a few great intros, such as Another Theory (winner at Main) and White one (winner at tUM). Hopefully we will see many intros using it at Revision.

The main feature of this release is the support for HLSL obfuscation, so we’ll now call this tool “Shader Minifier”. I got pretty good results with it, and I’ve been able to reduce the size of some famous 4k intros. Renaming strategy has been improved a bit; Detailed statistics will come later.

Try it now, download Shader Minifier!

  • HLSL Support. Please use –hlsl flag.
  • in/out now behave like uniform on global values (requested by several people), you can choose to preserve them.
  • Information on console output is removed unless you use -v (verbose).
  • Spaces in macros are now stripped (thanks to @lx!).
  • New flag –no-renaming to prevent from doing renaming.
  • Various fixes and improvements.

GLSL Minifier – smaller and smaller

The new version of our tool is released! Here is the changelog:

  • Allow forward declarations in the input code and remove them (functions are automatically reordered). Please use the syntax “int foo(int x)” and not “int foo(int)”.
  • More intelligent renaming based on the context the variable is used.
  • Allow structs in source code, fields are not renamed. Field names cannot look like vec fields (.rgb, .r…) because I haven’t written the typer yet.
  • Remove the –macro-threshold option. Will be fixed in a future version.
  • As usual, several bug fixes

The most important news is the improvement on the renaming strategy. In the 0.4 version, the Minifier tried to reuse the same variables again and again, and increased the frequency of a few characters. Now, it’s getting more complex: the name of a variable  depends on how it is used.

For instance, if you often call functions “max” and “mix”, you’ll often have the “x(” pattern. Thus, GLSL Minifier will probably name your function x to increase of the frequency of this pattern. The same goes for each two-char pattern the tool will find.

Here are some statistics I’ve just made, using shaders from 4k intros. I’ve taken a short C file, inserted the shader as a string, compiled, and compressed using Crinkler (/COMPMODE:SLOW /ORDERTRIES:3000). So, it’s all about making the shader compress better. Numbers are the filesize in bytes:

  • Retrospection
    • Original: 1462 (hand optimized)
    • Minifier 0.4: 1429
    • Minifier 0.5: 1421
  • Valleyball
    • Original: 2240 (using old BluFlame minifier)
    • Minifier 0.5: 2184
  • Another theory
    • Original: 1511 (hand optimized)
    • Minifier 0.4: 1475
    • Minifier 0.5: 1463
  • Lunaquatic
    • Minifier 0.4: 2635
    • Minifier 0.5: 2613
  • Sult
    • Minifier 0.4: 1411
    • Minifier 0.5: 1408
  • Slicesix
    • Minifier 0.4: 2493
    • Minifier 0.5: 2432

Conclusion: If you’re not using any tool to minify your GLSL shader, I bet you could save at least 20 bytes on your 4k intro. Try and see!

=> GLSL Minifier 0.5

GLSL Minifier, bug fix release

I’ve just fixed a few bugs in GLSL Minifier. Here is the list of changes for the 0.4.2 version:

  • Smaller file to download (700kb instead of 1.8Mb), using MPress. Thanks eyebex!
  • Print -.5 instead of -0.5. Thanks to stan_1901!
  • Parse octal and hexadecimal numbers. Bug found in Valleyball source code, thanks BluFlame!
  • Can compress several shaders at once, but only if the –preserve-externals flag is set.
  • Reorder uniform/varying/attribute declarations. This reduces the size of some shaders.
  • Fix a bug where the order of instructions was messed-up. Thanks to XT95!
  • Fix the –macro-threshold option. Thanks to Řrřola!
  • Forbid the reusing variable names in the same function (which is rejected by ATI compiler). Thanks again to Řrřola!
  • Handle multiline macros in the parser. Bug found in The Wind under my wing code, thanks Navis!
  • Improve the way the C header file is generated, trying to avoid name clashing. Thanks again eyebex!

My testing scripts are not fully set up, so you might find some other bugs. Please report them! If you use the –preserve-externals option, you might get name clashes if you use one letter names. That will be fixed another time.

Download GLSL Minifier

GLSL Minifier 0.4

We’ve just released GLSL Minifier 0.4! It fixes many problems, and add some new features. Tuesday update: version 0.4.1 improves a few things and adds an option to preserve external values, such as uniforms and varying. Here is the list of changes:

  • Command line is properly handled. Try the “-h” option to see the complete list of flags.
  • The -o option has been added, if you want to get the output in a particular file.
  • There is also a –shader-only, if you don’t want the C header and the formatted string.
  • Vectors accesses are made uniform, using (by default) only the “rgba” set. For instance, “foo.x” is renamed into “foo.r”.
  • Macros can be inserted to shorten external functions calls and types. This can greatly reduce the uncompressed output shader. However, the compressed file will most of the time be bigger (we’ve tested with Crinkler and kkrunchy). You can choose the threshold to control the number of macros that are inserted. This option is disabled by default.
  • The renaming algorithm has been changed. Previous versions of this tool were based on the GLSL 1.10 spec, which states that functions and variables use different namespaces. This is not true anymore since GLSL 1.20, so I had to remove a few tricks in the renamer & obfuscator.
  • The smoothstep function can be rewritten using IQ’s trick. It’s not done by default, because it’s not always a good thing to do.
  • Some information is now displayed on the console.
  • The –preserve-externals option has been added, so that you can use this compressor even if you have multiple shaders!

GLSL Minifier has been tested on the hand-optimized shader used in Retrospection, a great 4k intro (many thanks to FRequency and TITS who provided me the code). Here is the data:

Input file size is: 1727
File parsed. Shader size is: 1725
Rewrite tricks applied. Shader size is: 1723
Identifiers renamed. Shader size is: 1610
Macros added.
Minification finished. Shader size is: 1495

Note that this is the uncompressed size (size after macro injection is not useful). Once compiled with the C code and packed with Crinkler, it turns out we saved more than 30 bytes using this tool. If they had GLSL Minifier, FRequency and TITS could have improved even more their intro!

GLSL Minifier was also able to save a few bytes on To the Road of Ribbon, even if auld^titan spent time optimizing the intro to fit in 1k on Windows. Here is an example of output of the tool. See how it’s easy to include the file in your C/C++ project!

  1. #ifndef SHADER_CODE_H_
  2. #define SHADER_CODE_H_
  3. const char *shader_roadOfRibbon = ""
  4.  "float c=gl_Color.r*55;"
  5.  "float e(vec3 e)"
  6.  "{"
  7.    "return min(cos(e.r)+cos(e.g)+cos(e.b)+cos(e.g*20)*.02,length(max(abs(e-vec3(cos(e.b)*.2,cos(e.b)*.2-.5,0))-vec3(.2,.02,c+3),vec3(0))));"
  8.  "}"
  9.  "vec3 o(vec3 c)"
  10.  "{"
  11.    "return normalize(vec3(e(c+vec3(.02,0,0)),e(c+vec3(0,.02,0)),e(c+vec3(0,0,.02))));"
  12.  "}"
  13.  "void main()"
  14.  "{"
  15.    "vec3 v=vec3(cos(c),-cos(c*.5)*.5+.5,c),r=normalize(vec3(gl_FragCoord.rg*.002-1,1)),n=v;"
  16.    "for(int c=0;c<55;c++)"
  17.      "n+=r*e(n);"
  18.    "vec3 l=n+=r=reflect(r,o(n));"
  19.    "for(int c=0;c<55;c++)"
  20.      "n+=r*e(n);"
  21.    "gl_FragColor=abs(dot(o(n),vec3(.1)))+vec4(.2,cos(c*.5)*.5+.5,sin(c*.5)*.5+.5,1)*length(n-v)*.01+length(n-v)*.01+(1-min(l.g+2,1.))*vec4(1,.8,.7,1);"
  22.  "}";
  23. #endif // SHADER_CODE_H_

GLSL Minifier 0.3

Today is the new release of our GLSL obfuscator & minifier.

Here is the change log:

  • Feature: Variables that start with “i_” are now inlined. That will help you keep a clear code, name your values, while still having a short shader code.
  • Feature: The shader in the C code is now split into many lines (using quotes on every line), and indented. That will help you maintain the obfuscated GLSL code.
  • Improvement: The useless space that sometimes appeared after “else”, “do” and “return” is removed.
  • Bug fix: Postfix operators are now handled.
  • Bug fix: Some parenthesis were missing +various other fixes

Edit: I’ve just updated this 0.3 release to include a few additional fixes (mainly parse errors), thanks to Ponce.

GLSL Minifier 0.2 is out


GLSL Minifier has just been released. This is the first public version, but it’s still a preview. It has not been much tested, and probably contains bugs. However, I believe it’s usable and it should help intro coders a lot.

Changes since 0.1 version:

  • Bug fix: problems with field accesses
  • Bug fix: macros are now accepted (but ignored) in the user code
  • Feature: multiple declarations with the same type are now squeezed.
  • Feature: better renaming for the functions, they now have a separated namespace.
  • Feature: use overloaded functions in the generated code: if two functions don’t have the same number of parameters, they can have the same name.