opengl-glew

  1. opengl-glew
    1. Requirements
    2. Documentation
      1. GLEW functions
      2. GL helper functions
      3. gl-utils
        1. Vectors (srfi-4)
    3. Example
    4. Version history
      1. Version 0.7.0
      2. Version 0.6.0
      3. Version 0.5.0
      4. Version 0.4.4
      5. Version 0.3.0
      6. Version 0.2.0
      7. Version 0.1.0
    5. Source repository
    6. Author
    7. Licence

Bindings to OpenGL with GLEW extension loading.

Chicken's other opengl bindings are based on the old fixed function pipeline OpenGL. These bindings generated by bind with the OpenGL core header file. Additionally, bindings to GLEW are provided for extension management.

The opengl-glew egg provides two modules, an eponymous module that provides the main OpenGl and GLEW functionality, and gl-utils which provides various high-level functions.

Requirements

Documentation

All functions and constants from the OpenGL core header file are exported. Scheme style names are provided (underscores and camelCase replaced with hyphens), the gl prefix is removed from names, is functions are given question marks, and constants are bookended by +s (e.g. tex-image2d, enabled?, +arb-viewport-array+).

Functions whose C counterparts accept or return GLboolean accept or return a Scheme boolean value. Do not pass +true+ or +false+ to these functions.

GLEW functions

[procedure] (init)

Required to initialize GLEW/OpenGL. An OpenGL context must be created before this is called.

[procedure] (supported? EXTENSION-NAME)

Query whether the OpenGL extension, given as a string, is supported.

GL helper functions

The functions in this section are part of the opengl-glew module, rather than gl-utils because they either provide a direct interface to an OpenGL function in a more Scheme-like fashion, or they simplify fundamental operations that rarely must be performed differently.

[procedure] (make-shader TYPE SOURCE)

Creates and compiles a shader object given the shader's type (e.g. +vertex-shader+, +geometry-shader+, +fragment-shader), and a string containing the GLSL source. Returns an integer representing the ID of the shader.

[procedure] (make-program SHADER-LIST [PROGRAM-ID])

Creates and links a program object, given a list of shader objects (i.e. the integers returned by make-shader. Returns an integer representing the ID of the program.

Accepts an optional PROGRAM-ID argument. If given, make-program will use this ID rather than generating a new one.

[procedure] (gen-buffer)
[procedure] (gen-framebuffer)
[procedure] (gen-program-pipeline)
[procedure] (gen-query)
[procedure] (gen-renderbuffer)
[procedure] (gen-sampler)
[procedure] (gen-texture)
[procedure] (gen-transform-feedback)
[procedure] (gen-vertex-array)

Analogous to their pluralized counterparts, but only generates and returns one (integer) object.

[procedure] (delete-buffer BUFFER)
[procedure] (delete-framebuffer FRAMEBUFFER)
[procedure] (delete-program-pipeline PROGRAM-PIPELINE)
[procedure] (delete-query QUERY)
[procedure] (delete-renderbuffer RENDERBUFFER)
[procedure] (delete-sampler SAMPLER)
[procedure] (delete-texture TEXTURE)
[procedure] (delete-transform-feedback TRANSFORM-FEEDBACK)
[procedure] (delete-vertex-array VERTEX-ARRAY)

Analogous to their pluralized counterparts, but only accepts and deletes one (integer) object.

[procedure] (check-error)

Performs get-error (glGetError) and prints the error type when an error is returned.

gl-utils

gl-utils provides functions for creating VAOs, and loading PLY files.

[procedure] (make-vao VERTEX-DATA INDEX-DATA ATTRIBUTES [USAGE])

make-vao generalizes the typically repetitious code used to initialize vertex attribute objects. It deals with the case of having packed vertex data (VERTEX-DATA) and a vector of indices (INDEX-DATA) for those vertexes. This data may be passed as any sort of (srfi-4) vector or a blob.

ATTRIBUTES is the list of data necessary for the vertex attributes, in the form of ((LOCATION TYPE N [normalize?: NORMALIZE?]) ...). LOCATION is the attribute location, TYPE is the type of data corresponding to the given attribute, given as a keyword. For possible types, see type->gl-type. N is the number of elements for the given attribute. The keyword normalize?: accepts a boolean argument which instructs OpenGL to normalize the attribute or not. Defaults to #f.

The optional USAGE must be one of +stream-data+, +stream-read+, stream-copy, +static-data+, +static-read+, static-copy, +dynamic-data+, +dynamic-read+, dynamic-copy. Defaults to +static-draw+.

make-vao returns the ID of a vertex array object. This object should be deleted with delete-vertex-array when no longer used. Intermediate vertex buffers are generated and deleted, thus only the returned vertex array ID needs to be managed.

[procedure] (load-ply FILE BUFFER-SPEC)

Loads a PLY file. FILE is a path that may be pointing to a gziped PLY file. BUFFER-SPEC is a list in the form ((NAME VARS) ...) where NAME is the name of an element in the PLY file and VARS is either a list of property names or, in the case of a property list, a single name. Two values are returned: a list of u8vectors which correspond to the buffers named in BUFFER-SPEC and a list of the elements that are in the PLY file in the form of:

   (element-name n-elements (property-name property-type))

Or, when an element is a property list:

   (element-name n-elements (property-name (list: list-length-type element-type)))

The buffers returned are packed with the contents of the properties named in the BUFFER-SPEC. Thus, for a PLY file that has element vertex with properties float x, float y, float z, float confidence, uchar r, uchar g, and uchar b, as well as a nelement face with a property list uchar ushort vertex_index, the following BUFFER-SPEC could be used:

   (load-ply "example.ply.gz" '((vertex: (x y z r g b)) (face: vertex_index)))

This buffer spec would result in a list of two u8vectors being returned: one with the packed elements corresponding to properties x, y, z, r, g, and b (with the corresponding property types), and the second containing the vertex indices.

[procedure] (load-ply-vao FILE vertex: VERTEX face: FACE)

Similar to load-ply, but returns a number of values:

FILE is a PLY file (which may be gziped). The PLY file must contain at least the elements vertex and face (other elements will be ignored). VERTEX is a list of (attribute-location property-name ...) elements, which specifies how the vertex buffers of the VAO will be arranged. All properties named by each element of VERTEX must be of the same type. FACE is the name of the face property list.

Again, for a PLY file that has element vertex with properties float x, float y, float z, float confidence, uchar r, uchar g, and uchar b, as well as a element face with a property list uchar ushort vertex_index, the following could be used:

   (load-ply-vao "example.ply" vertex: `((,vertex-location x y z) 
                                         (,color-location r g b))
                               face: vertex_index)
   
[procedure] (type->gl-type TYPE)

Converts the keyword TYPE into a OpenGL type enum value. Accepted types (grouped by synonyms) are:

Vectors (srfi-4)

gl-utils reexports a version of srfi-4 that gives preference to vectors being created in non-garbage collected memory. This is useful for use with OpenGL, since it is often desirable to pass vectors to OpenGL that will remain in one place. All srfi-4 functions not mentioned below are reexported without changes.

The NNNvector and list->NNNvector constructors have been modified so that they return vectors in non-garbage collected memory.

The make-NNNvector constructors act as their srfi-4 counterparts, except they now return vectors in non-garbage collected memory by default.

Additionally, the following non-srfi-4 procedures are exported:

[procedure] (->pointer VECTOR)

Returns the pointer to a srfi-4 vector or blob.

[procedure] (size VECTOR)

Returns the size, in bytes, of a srfi-4 vector or blob.

Example

This example depends on the glfw3 egg for window and context creation, and the gl-math egg for matrix math.

    
(import chicken scheme)
(use (prefix glfw3 glfw:) (prefix opengl-glew gl:) gl-math gl-utils)

(define *vertex* 
#<<END
#version 330
in vec2 vertex;
in vec3 color;
out vec3 c;
uniform mat4 MVP;

void main(){
   gl_Position = MVP * vec4(vertex, 0.0, 1.0);
   c = color;
}
END
)

(define *fragment*
#<<END
#version 330
in vec3 c;
out vec4 fragColor;
void main(){
  fragColor = vec4(c, 1.0);
}
END
)

(define vertex-data (f32vector -1 -1 1 0 0
                               1 -1 0 1 0
                               1 1 0 0 1
                               -1 1 1 0 1))

(define index-data (u16vector 0 1 2
                              0 2 3))

(define vao (make-parameter #f))

(define program (make-parameter #f))

(define projection-matrix
  (perspective 640 480 0.1 100 70))

(define view-matrix
  (look-at 1 0 3
           0 0 0
           0 1 0))

(define model-matrix (mat4-identity))

(define (render)
  (gl:use-program (program))
  (gl:uniform-matrix4fv (gl:get-uniform-location (program) "MVP")
                        1 #f
                        (m* projection-matrix
                            (m* view-matrix model-matrix)))
  (gl:bind-vertex-array (vao))
  (gl:draw-elements-base-vertex gl:+triangles+ 6 (type->gl-type ushort:) #f 0)

  (gl:check-error)
  (gl:bind-vertex-array 0))

(glfw:with-window (640 480 "Example" resizable: #f)
  (gl:init)

  (print (gl:supported? "GL_ARB_framebuffer_object"))

  (set! *vertex* (gl:make-shader gl:+vertex-shader+ *vertex*))
  (set! *fragment* (gl:make-shader gl:+fragment-shader+ *fragment*))

  (program (gl:make-program (list *vertex* *fragment*)))

  (vao (make-vao vertex-data index-data
                 `((,(gl:get-attrib-location (program) "vertex") float: 2)
                   (,(gl:get-attrib-location (program) "color") float: 3))))
  (let loop ()
     (glfw:swap-buffers (glfw:window))
     (gl:clear (bitwise-ior gl:+color-buffer-bit+ gl:+depth-buffer-bit+))
     (render)
     (glfw:poll-events)
     (unless (glfw:window-should-close (glfw:window))
       (loop))))

Version history

Version 0.7.0

8 August 2014

Version 0.6.0

17 June 2014

Version 0.5.0

3 June 2014

Version 0.4.4

2 June 2014

Version 0.4.3

30 May 2014

Version 0.4.2

24 May 2014

Version 0.4.1

12 May 2014

Version 0.4.0

11 May 2014

Version 0.3.0

Version 0.2.0

Version 0.1.0

Source repository

Source available on GitHub.

Bug reports and patches welcome! Bugs can be reported via GitHub or to alex.n.charlton at gmail.

Author

Alex Charlton

Licence

BSD