# glls glls (GL Lisp Shaders) lets you write [GLSL](https://www.opengl.org/documentation/glsl/) (OpenGL Shader Language) shaders in a convenient pseudo-scheme language in Chicken Scheme. The compilation into GLSL happens at compile-time for zero run-time cost. Run-time compilation and dynamic recompilation is also supported. To those that want to dynamically construct shaders: I solute you. In addition to the eponymous module, glls also provides the `glls-render` module. `glls-render` enhances glls to create automatic rendering functions for each pipeline. When compiled, these rendering functions are created in efficient C, although dynamic functions are also provided. See the section [Automatic render functions](#automatic-render-functions) for details. The idea for glls was hugely inspired by [Varjo](https://github.com/cbaggers/varjo). Before learning about Varjo, I had never considered the possibility of writing shaders in anything but the GLSL. Seeing them being written in Lisp was a major, "Of course!" moment. That said, while this library bears some superficial resemblance to Varjo, the approach is quite different. While Varjo does a lot of work to validate the the lispy-glls expressions (including type checking), glls only performs cursory syntactic checking. The result of this is that one could probably write shaders in Varjo without knowing the GLSL and could be reasonably sure that those shaders would always compile to something that would mostly work. glls makes no such promises, so it is entirely possible to generate GLSL that won’t compile. Being able to understand GLSL code is therefore a prerequisite for successful shader debugging. The GLSL code output by glls is beautifully formatted, thanks to Alex Shinn’s amazing [fmt](http://synthcode.com/scheme/fmt/) library. fmt is responsible for far more than just the GLSL formatting, since it is basically a compiler of its own. The compilation portion of glsl is more or less a thin layer on top of fmt. ## Installation This repository is a [Chicken Scheme](http://call-cc.org/) egg. It is part of the [Chicken egg index](http://wiki.call-cc.org/chicken-projects/egg-index-4.html) and can be installed with `chicken-install glls`. ## Requirements * make * fmt * matchable * miscmacros * opengl-glew * srfi-42 ## Documentation [parameter] glsl-version The default GLSL version used by shaders. Defaults to `330`. ### Shaders [record] (shader TYPE SOURCE INPUTS OUTPUTS UNIFORMS PROGRAM) Used to represent shaders. Returned by `define-shader` and `create-shader`. It should not typically be necessary to access the slots of this record. [macro] (define-shader SHADER-NAME GLLS-SHADER) Defines a new `shader` named `NAME`. The (unquoted) form `GLLS-SHADER` should conform to language defined in the section [The glls shader language](#the-glls-shader-language). Before shaders are used, they must be compiled by OpenGL with `compile-shader`. [procedure] (create-shader GLLS-SHADER ) Creates (at run-time) a new `shader`. The form `GLLS-SHADER` should conform to language defined in the section [The glls shader language](#the-glls-shader-language). Before shaders are used, they must be compiled by OpenGL with `compile-shader`. [procedure] (compile-glls GLLS-SHADER) Returns the source string for a shader. The form `GLLS-SHADER` should conform to language defined in the section [The glls shader language](#the-glls-shader-language). [procedure] (compile-shader SHADER) Compile (in OpenGL) `SHADER`. Nothing is done if the shader has already been compiled. This typically does not need to be called, since `compile-pipeline` does so. Must be called while there is an active OpenGL context. ### Pipelines *Pipelines* are the term that glsl uses to describe a collection of shaders that will be linked together. This is equivalent to a GL *program*, just less ambiguously named. [record] (pipeline SHADERS ATTRIBUTES UNIFORMS PROGRAM) Created with `define-pipeline` or `create-pipeline`, contains the data needed for a pipeline. `SHADERS` is the list of shader records. `ATTRIBUTES` and `UNIFORMS` are lists of the attributes and uniforms of the shader, specified as `(name . type)` pairs before compilation (with `compile-pipeline` or `compile-pipelines`) and `(name location type)` lists after compilation. `PROGRAM` is the GL ID of the program (always 0 before compilation). [macro] (define-pipeline PIPELINE-NAME . SHADERS) Defines a new `pipeline` named `NAME`. The `SHADERS` should either be forms conforming to language defined in the section [The glls shader language](#the-glls-shader-language), `shader`s defined by `define-shader`, or a mix of the two. Pipelines must have at least one vertex and one fragment shader to be able to compile. Before pipelines are used, they must be compiled by OpenGL with `compile-pipeline` or `compile-pipelines`. `define-pipeline` behaves differently when it is being evaluated *and* when a given pipeline is being redefined. In this case, the new pipeline inherits the GL program ID of the old one. Additionally, the pipeline is compiled by OpenGL right away (and as a consequence, so are any pipelines that are pending compilation). This is done so that pipelines can be edited and reevaluated in a REPL session and one’s scene will be updated as expected. See the [interactive example](https://github.com/AlexCharlton/glls/blob/master/examples/interactive.scm) for an example of how this can be accomplished. `define-pipeline` has additional effects when used with the `glls-render` module (see [Automatic render functions](#automatic-render-functions)). [procedure] (create-pipeline . SHADERS) Creates (at run-time) a new `pipeline`. The `SHADERS` should either be forms conforming to language defined in the section [The glls shader language](#the-glls-shader-language), `shader`s, or a mix of the two. Pipelines must have at least one vertex and one fragment shader to be able to compile. Before pipelines are used, they must be compiled by OpenGL with `compile-pipeline` or `compile-pipelines`. [procedure] (compile-pipeline PIPELINE) Compile (in OpenGL) the `PIPELINE` and sets its `PROGRAM` slot to the OpenGL program ID. If the pipeline’s `PROGRAM` slot is already set to a non-zero value, this ID will be reused for the new program. Compiles all of the pipeline’s shaders with `compile-shader`. Must be called while there is an active OpenGL context. [procedure] (compile-pipelines) Compile (as per `compile-pipeline`) all the pipelines defined by `define-pipeline` and `create-pipeline`. Must be called while there is an active OpenGL context. [procedure] (pipeline-uniform UNIFORM PIPELINE) Return the location of `UNIFORM`. The `PIPELINE` must be compiled before this function can be used. [procedure] (pipeline-attribute ATTRIBUTE PIPELINE) Return the location of `ATTRIBUTE`. The `PIPELINE` must be compiled before this function can be used. ### The glls shader language #### Shader syntax The shaders of glls – the forms that `define-shader`, `define-pipeline`, etc. expect – have the following syntax: ( [input: ] [uniform: ] [output: ] [version: ] [extensions: ] [pragmas: ] [use: ] [export: ... `type` is the keyword type of the shader. It must be one of `#:vertex`, `#:fragment`, `#:geometry`, `#:tess-control`, `#:tess-evaluation`, or `#:compute`. `inputs` is a list of the input variables for the shader. These are given in `(name type)` lists. `uniforms` is a list of the uniform variables for the shader. These are given in `(name type)` lists. `outputs` is a list of the output variables from the shader. These are given in `(name type)` lists. `version` is the integer version number of the shader, i.e. the number you would write at the top of the shader source (e.g. `#version 410`). Defaults to the `glsl-version` parameter. `extensions` is the list of GLSL extensions desired (in string form). E.g. `("GL_EXT_gpu_shader4 : enable")`. Defaults to `()` `pragmas` is the list of GLSL pragmas desired (in string form). E.g. `("optimize(on)")`. Defaults to `()` `imports` is the list of shaders that the current shader depends on. See the section [Shaders that export](#shaders-that-export) for more details. Defaults to `()` `exports` is the list of symbols that the current shader exports. See the section [Shaders that export](#shaders-that-export) for more details. Defaults to `()` `body` is the form representing the code of the shader. See the section [Shader Lisp](#shader-lisp) for an explanation of the kind of code that is expected. #### Shader Lisp For the most part, the Lisp used to define glls shaders looks like Scheme with one notable difference: types must be specified whenever a variable or function is defined. Under the hood, forms are being passed to [fmt](https://wiki.call-cc.org/eggref/4/fmt#c-as-s-expressions), so everything that you can do there will work in glls. Details of the Lisp used for shaders is provided in the following sections. It should be possible to do almost anything in glls that you would want to do with the GLSL. Known exceptions to this is are: layout qualifiers (which I don’t feel are terribly relevant in the context of Scheme, at least not until uniform locations become prevalent), do-while loops (which have no Scheme analog), uniform blocks (for no good reason), `#error`, `#line`, `#undef`, and struct uniforms (implementation reasons). Let me know if there are any features that you find lacking. Keep in mind that glls cannot do anything that the GLSL can’t, such as making anonymous or recursive functions. ##### Variables and naming Symbols in glls are transformed from a Scheme style into the C style used in the GLSL. Letters after dashes are uppercased (i.e., symbols become camelCased). Symbols prefixed by `gl:` in glls become prefixed by `gl_` in GLSL. `#f` and `#t` may be used instead of `false` and `true`. For programmer-defined variables this has little consequence. The importance of learning the renaming conventions comes when you want to call GLSL functions or variables. Examples of mappings between glls and GLSL names are: `gl:position` → `gl_Position`, `float-bits-to-uint` → `floatBitsToUint`, `shadow-2d-proj-lod` → `shadow2DProjLod`, and `sampler-2d-ms-array` → `sampler2DMSArray`. Two special cases are `emit-vertex` and `end-primitive` which are translated into the functions `EmitVertex` and `EndPrimitive` respectively (which, for some reason, go against the usual GLSL naming conventions). ##### Types When defining variables or functions in glls, types must be supplied. Basic types (e.g. `int`, `mat2x2`) are given either as a symbol or keyword (e.g. `int`, `#:mat2x2`), whichever is preferred. Types with qualifiers (e.g. `lowp float`, `out mediump vec2`) are given as lists (e.g. `(lowp float)`, `(out mediump vec2)`). Arrays are specified as lists beginning with the keyword `#:array`. The next element in the list is the type, while the optional third element is the size. E.g. `(#:array int 5)`. When used with qualifiers, the array takes the place of the type, e.g. `(highp (#:array float))`. ##### Functions GLSL functions and operators are all called like normal Lisp functions. In almost all cases the GLSL symbol (taking into account the renaming described in [Variables and naming](#variables-and-naming) can be used, while many operators can be called with their Scheme counterpart. The only operators that may not be used directly are `|`, `||`, `|=`, `.`, `=`, and array reference which must be called with their counterparts. The following is a mapping between glls aliases for GLSL functions and operators: * `modulo`: `%` * `expt`: `pow` * `equal?`, `eqv?`, `eq`, `=`: `==` * `set!`: `=` * `and`: `&&` * `or`: `||` * `not`: `!` * `bitwise-and`, `bit-or`: `&` * `bitwise-ior`, `bit-or`: `|` * `bitwise-xor`, `bit-xor`: `^` * `bitwise-not`, `bit-not`: `~` * `arithmetic-shift`: `<<` * `field`, `..`: `.` (struct field reference, e.g. `(field point x)` → `point.x`) * `swizzle`, `~~`: `.` (vector swizzling, e.g. `(swizzle color r g)` → `color.rg`) * `array-ref`, `vector-ref`: `[]` (array reference, e.g. `(array-ref a 4)` → `a[4]`) * `length`: `.length()` (vector length, e.g. `(length vec)` → `vec.length()`) ##### Definition Variables, functions, and records (structs) are defined much like they are in Scheme, with the additional requirement of including types. (define []) Defines the variable `name`. When `type` is an array, a vector literal (eg. `#(1 2 3)`) may be used. (define ( [( ) ...]) ...) Defines the function `name`. The last expression in the body of a non-void function is automatically returned. If `body` is omitted, a function prototype is created. (let (( []) ...) ...) Defines the supplied variables. When `type` is an array, a vector literal (eg. `#(1 2 3)`) may be used. Note that, unlike Scheme, the variables created will continue to exist outside of the `let` (until the extent of whatever lexical scope the `let` exists within). In other words, `let` does not introduce scope. Note also that variables defined in `let` are within the scope of variables that are subsequently defined in the same `let` (i.e. `let` functions like `let*` in Scheme, and in fact `let*` may be used if preferred). (define-record ( ) ...) Defines the struct `name`. ##### Control The following can be used with identical syntax to scheme: (if []) (cond ( ...) ... (else )) (case (( ...) ...) ... (else )) (begin ...) Keep in mind that they may only be used in the same place as their corresponding GLSL statements, with the exception of `begin`, which can only be used where it is possible to have multiple expressions. ##### Iteration (for ...) GLSL style `for` loop. (do-times ( [] ) ...) Equivalent to `(for (define #:int ) (< ) (++ ) ...)`. `start` defaults to 0. (while ...) GLSL style `while` loop. ##### Jumps All GLSL jumps (`continue`, `break`, `return`, `discard`) can be called like functions. Return may accept one argument. Keep in mind that the last expression in a non void function is automatically returned. ##### Pre-processor The following forms can be used to add pre-processor directives: (%define []) (%if []) (%ifdef []) (%ifndef []) ### Shaders that export It is often desirable to have shaders that contain generic, reusable functions. These shaders are linked into the pipeline (or program, in GLSL parlance) so that they can be accessed by other shaders. In order for another shader to reuse a function, it first has to (as in C) include a function prototype. glsl automates this process. glls lets you define shaders that export symbols through the use of the [`export` keyword](#shader-syntax). These shaders can then be imported by others (through the [`use` keyword](#shader-syntax)). Prototypes are automatically generated for top-level functions or variables whose names match the symbols in the `export` keyword list. These prototypes are then inserted into shaders that `use` the exporting shader. Shaders that are `use`d by another are automatically linked into the resulting pipeline. Shaders that export should not have any inputs or outputs. See the example [exports.scm](https://github.com/AlexCharlton/glls/blob/master/examples/exports.scm) to see this in action. ### Automatic render functions By using the `glls-render` module, you can have glls automatically generate a function that will render an object with your glls shader. `glls-render` exports a new `define-pipeline` that defines a set of functions used for rendering and managing the objects that will be rendered. `glls-render` should not be used with the `glls` module: It reexports everything that you need from `glls`. Recalling `define-pipeline`: (define-pipeline PIPELINE-NAME . SHADERS) There is one difference that you need to know when calling `glls-render`’s `define-pipeline`: All shaders must include a list of the shader’s uniforms since the uniforms are the important information needed to derive rendering functions. This means that if you previously define some shaders (for example: `my-vertex-shader` and `my-fragment-shader`) and you wish to combine them in a pipeline, you *must* include the uniforms in the pipeline definition. This is done with a list that takes the form `(SHADER uniform: [UNIFORM] ...)`. This list must be present even if the shader does not use any uniforms. For example: (define-pipeline my-pipeline (my-vertex-shader uniform: mvp-matrix inverse-transpose-matrix) (my-fragment-shader uniform:)) Of course, if you are defining the shaders in the pipeline, then a separate list of uniforms is not necessary. `glls-render` causes `define-pipeline` to define several new functions. First is `render-PIPELINE-NAME`. `render-PIPELINE-NAME` takes one argument: a renderable object (see [Renderables](#renderables)). The `render-PIPELINE-NAME` function works differently depending on whether the `define-pipeline` has been compiled or interpreted (although the end results should stay the same). When `define-pipeline` is compiled, the resulting `render-PIPELINE-NAME` function is compiled directly to efficient (non-branching) C. When `define-pipeline` is interpreted, `render-PIPELINE-NAME` calls a generic rendering function that is not nearly as fast. #### Renderables In order to use one of the automatically generated render functions, you must have something to render. That’s why `define-pipeline` also defines a function that constructs a renderable object: `make-SHADER-NAME-renderable`. This function takes a number of keyword arguments: - `vao:` – A VAO such as those returned by [opengl-glew’s `make-vao`](http://api.call-cc.org/doc/opengl-glew/make-vao). I.e.: A VAO that binds an array of attributes – for each element in the pipeline – as well as an element array. - `mode:` – The drawing mode to use when drawing the elements of the VAO. Must be one of (opengl-glew’s): `+points+`, `+line-strip+`, `+line-loop+`, `+lines+`, `+line-strip-adjacency+`, `+triangles+`, `+triangle-strip+`, `+triangle-fan+`, `+triangles-adjacency+`, `+triangle-strip-adjacency+`, or `+patches+`. Defaults to `+triangles+`. - `n-elements:` – The number of elements (vertices) to draw. - `element-type:` – The type of the values in the VAO’s element array. Must be one of `+unsigned-byte+`, `+unsigned-short+`, or `+unsigned-int+`. - `offset:` – A byte offset to the location of the desired indices to draw. - `data:` – An optional pointer to an appropriate glls renderable object. If not provided, a fresh renderable object will be created. [gllsRenderable.h](https://github.com/AlexCharlton/glls/blob/master/gllsRender.h) defines the structs used for renderables. Which struct is used for a given pipeline is chosen based on the number of uniforms present in the pipeline. See the [`glDrawElements` documentation](https://www.opengl.org/sdk/docs/man/html/glDrawElements.xhtml) for more information about these expected arguments. `make-SHADER-NAME-renderable` also expects one keyword argument for each uniform in the pipeline. These arguments should either be an f32vector, an s32vector, a u32vector, a pointer to the uniform data, or – in the case of a texture – a fixnum. Even if the uniform is a single value (e.g. a float), it must still be passed as a vector (or a pointer). This lets the value of the uniform be updated independently of the renderable. Additionally, `define-pipeline` defines a number of renderable setters for each of the keyword arguments accepted by `make-SHADER-NAME-renderable`. These are named: - `set-SHADER-NAME-renderable-vao!` - `set-SHADER-NAME-renderable-mode!` - `set-SHADER-NAME-renderable-n-elements!` - `set-SHADER-NAME-renderable-element-type!` - `set-SHADER-NAME-renderable-offset!` And for each uniform in the pipeline, `set-SHADER-NAME-renderable-UNIFORM-NAME!` is created. [procedure] (renderable-size PIPELINE) Returns the size, in bytes, of the memory needed for a renderable belonging to `PIPELINE`. #### Fast render functions When compiled, the render function defined by `define-pipeline` is actually a combination of three “fast” render functions: a begin render function, a render function, and an end render function. This is done so that, if desired, all of the renderables that belong to the same pipeline may be rendered at the same time, without needing to perform expensive calls like program changes or texture binding more than once. To use these functions, simply call the begin render function with the first renderable, then call the render function on all renderables (including the first), finally calling the end render function (with no arguments) to clean up. `define-pipeline` does not define all of these functions separately, but instead defines a single function with which to access them: `PIPELINE-NAME-fast-render-functions`. This function returns six values: the begin render function, the render function, the end render function, and pointers to those same C functions in that order. One major assumption must be kept in mind while working with the fast render functions: textures are only bound once. In other words: it is assumed that that all of the renderables belonging to the same pipeline share a common “sprite sheet” (or other shared texture type). If this assumption does not hold true, simply use the standard render function, or call the begin render function for every set of renderables that uses a separate texture. #### Utilities [macro] (export-pipeline PIPELINE) Since glls-render causes `define-pipeline` to define multiple functions, this macro exports everything related to `PIPELINE`. [procedure] (load-ply-renderable PLY RENDERABLE-MAKER . ARGS) Load the given PLY file and return a renderable. Returns three values: a renderable, the vertex data blob, and the index data blob. `PLY` is a PLY file name such as those accepted by opengl-glew’s [`load-ply`](http://api.call-cc.org/doc/opengl-glew/load-ply). `RENDERABLE-MAKER` is the function used to construct the renderable of the desired pipeline. `ARGS` are the keyword arguments that must include `vertex:` and a `face:` arguments (as per [`load-ply-vao`](http://api.call-cc.org/doc/opengl-glew/load-ply-vao)) as well as arguments for each uniform (as per the renderable maker function). ## Examples These examples depends on the [glfw3](http://wiki.call-cc.org/eggref/4/glfw3) egg for window and context creation. The examples presented here illustrate only very basic shader definition and loading. For more complete examples, see the [examples directory](https://github.com/AlexCharlton/glls/tree/master/examples) of the source. Aside from knowing how to write glls shaders, only one macro, one function, and one record is necessary to use glls: `define-pipeline`, `compile-pipelines`, and the record `pipeline`. This example illustrates this minimal pipeline creation ``` Scheme (import chicken scheme) (use glls (prefix glfw3 glfw:) (prefix opengl-glew gl:)) (define-pipeline foo ((#:vertex input: ((vertex #:vec2) (color #:vec3)) uniform: ((mvp #:mat4)) output: ((c #:vec3))) (define (main) #:void (set! gl:position (* mvp (vec4 vertex 0.0 1.0))) (set! c color))) ((#:fragment input: ((c #:vec3)) output: ((frag-color #:vec4))) (define (main) #:void (set! frag-color (vec4 c 1.0))))) (glfw:with-window (640 480 "Example" resizable: #f) (gl:init) (compile-pipelines) (print foo) (gl:use-program (pipeline-program foo))) ``` This example is similar to the first, but also illustrates the ability to define pipelines in different ways. ``` Scheme (import chicken scheme) (use glls (prefix glfw3 glfw:) (prefix opengl-glew gl:)) (define-pipeline foo ((#:vertex input: ((vertex #:vec2) (color #:vec3)) uniform: ((mvp #:mat4)) output: ((c #:vec3))) (define (main) #:void (set! gl:position (* mvp (vec4 vertex 0.0 1.0))) (set! c color))) ((#:fragment input: ((c #:vec3)) output: ((frag-color #:vec4))) (define (main) #:void (set! frag-color (vec4 c 1.0))))) (define-shader bar (#:vertex input: ((vertex #:vec2) (color #:vec3)) uniform: ((mvp #:mat4)) output: ((c #:vec3))) (define (main) #:void (set! gl:position (* mvp (vec4 vertex 0.0 1.0))) (set! c color))) (define-pipeline baz bar (cadr (pipeline-shaders foo))) (glfw:with-window (640 480 "Example" resizable: #f) (gl:init) (compile-pipelines) (print foo) (print baz)) ``` ## Version history ### Version 0.5.2 24 August 2014 - Update to new gl-utils **Version 0.5.1** - Allow `#t`, `#f` - Fix swizzle **Version 0.5.0** 14 August 2014 - New shader syntax ### Version 0.4.1 12 August 2014 - Fix export name matching **Version 0.4.0** 11 August 2014 - Add shader exports - Add function prototyping - Add `export-pipeline` - Add aliases to `field`, `swizzle` (`..`, `~~`) - Export `renderable-size` rather than `allocate-renderable` - Improve error messages - Bug fixes ### Version 0.3.3 4 June 2014 - Bug fixes relating to dynamic reevaluated pipelines **Version 0.3.2** 3 June 2014 - Update examples for GC safety **Version 0.3.1** 2 June 2014 - Fix `load-ply-renderable` - Fix gllsRender.h **Version 0.3.0** 30 May 2014 - Support dynamic reevaluation of pipelines ### Version 0.2.2 29 May 2014 - Add make as a dependency **Version 0.2.1** - Fix bug affecting dynamic use of glls-render **Version 0.2.0** 28 May 2014 - Automatic render function generation - Removed `eval` from `defpipeline` (which broke some things when used in modules) - Renamed `defpipeline`, `defshader` ### Version 0.1.0 * Initial release ## Source repository Source available on [GitHub](https://github.com/AlexCharlton/glls). Bug reports and patches welcome! Bugs can be reported via GitHub or to alex.n.charlton at gmail. ## Author Alex Charlton ## Licence BSD