(defpackage #:clog-tut-34

(:use #:cl #:clog #:clog-webgl)

(:export start-tutorial))

(in-package :clog-tut-34)

;; example based on - https://webgl2fundamentals.org/webgl/lessons/webgl-fundamentals.html

;; "#version 300 es" MUST BE THE VERY FIRST LINE OF YOUR SHADER.

;; No comments or blank lines are allowed before it

(defparameter *vertex-shader-source* "#version 300 es

// an attribute is an input (in) to a vertex shader.

// It will receive data from a buffer

in vec4 a_position;

// all shaders have a main function

void main() {

// gl_Position is a special variable a vertex shader

// is responsible for setting

gl_Position = a_position;

}")

(defparameter *fragment-shader-source* "#version 300 es

// fragment shaders don't have a default precision so we need

// to pick one. highp is a good default. It means \"high precision\"

precision highp float;

// we need to declare an output for the fragment shader

out vec4 outColor;

void main() {

// Just set the output to a constant reddish-purple

outColor = vec4(1, 0, 0.5, 1);

}")

(defun on-new-window (body)

(debug-mode body)

(setf (title (html-document body)) "Tutorial 34")

(let* ((canvas (create-canvas body :width 1000 :height 500))

(gl (create-webgl canvas))

(vertex-shader (compile-shader-source gl :VERTEX_SHADER *vertex-shader-source*))

(fragment-shader (compile-shader-source gl :FRAGMENT_SHADER *fragment-shader-source*))

(program (compile-webgl-program gl vertex-shader fragment-shader))

(pos (attribute-location program "a_position"))

(pos-buffer (create-webgl-buffer gl))

(vao (create-vertex-array gl)))

(dotimes (n (parse-integer (program-parameter program :ACTIVE_ATTRIBUTES)))

(let ((obj (active-attribute program n)))

(format t "~A : Active Attribute - ~A ~A ~A"

n (info-name obj) (info-size obj) (info-type obj))))

(dotimes (n (parse-integer (program-parameter program :ACTIVE_UNIFORMS)))

(let ((obj (active-uniform program n)))

(format t "~A : Active Uniform - ~A ~A ~A"

n (info-name obj) (info-size obj) (info-type obj))))

(print (drawing-buffer-width gl))

(print (drawing-buffer-height gl))

(bind-buffer pos-buffer :ARRAY_BUFFER)

(buffer-data pos-buffer `(0 0

0 0.5

0.7 0)

"Float32Array" :STATIC_DRAW)

(bind-vertex-array vao)

(enable-vertex-attribute-array gl pos)

(vertex-attribute-pointer gl pos 2 :FLOAT nil 0 0)

(viewport gl 0 0 (width canvas) (height canvas))

(clear-color gl 0.0 0.0 0.0 1.0)

(clear-webgl gl :COLOR_BUFFER_BIT)

(use-program program)

(bind-vertex-array vao)

(draw-arrays gl :TRIANGLES 0 3)))

(defun start-tutorial ()

"Start turtorial."

(initialize 'on-new-window)

(open-browser))