debug.lisp

(in-package #:org.shirakumo.fraf.trial)

(define-shader-entity debug-draw-text (standalone-shader-entity)
  ((text-vao :accessor text-vao)
   (text :accessor text)))

(defmethod initialize-instance :after ((draw debug-draw-text) &key)
  (setf (text draw) (make-array 256 :fill-pointer 0 :adjustable T :element-type 'single-float))
  (let ((vbo (make-instance 'vertex-buffer :buffer-data (text draw))))
    (setf (text-vao draw) (make-instance 'vertex-array :vertex-form :triangles :bindings
                                         `((,vbo :size 3 :offset 0 :stride 20 :index 0)
                                           (,vbo :size 2 :offset 12 :stride 20 :index 2))))))

(defmethod stage :after ((draw debug-draw-text) (area staging-area))
  (stage (text-vao draw) area)
  (stage (// 'trial 'ascii) area))

(defmethod render ((draw debug-draw-text) (program shader-program))
  (setf (uniform program "view_matrix") (view-matrix))
  (setf (uniform program "projection_matrix") (projection-matrix))
  (setf (uniform program "texture_image") (bind (// 'trial 'ascii) :texture0))
  (render-array (text-vao draw) :vertex-count (truncate (length (text draw)) 5)))

;; FIXME: this is not correct atm since we billboard globally, rather than
;;        billboarding around the text's origin. To do this we'd somehow have
;;        to access the origin of each text element in the vertex shader,
;;        which isn't trivial.
(define-class-shader (debug-draw-text :vertex-shader)
  "layout (location = 0) in vec3 position;
layout (location = 2) in vec2 i_uv;
out vec2 v_uv;

uniform sampler2D texture_image;
uniform mat4 view_matrix;
uniform mat4 projection_matrix;

void main(){
  mat4 modelView = view_matrix;
  modelView[0][0] = 1.0; modelView[0][1] = 0.0; modelView[0][2] = 0.0;
  modelView[1][0] = 0.0; modelView[1][1] = 1.0; modelView[1][2] = 0.0;
  modelView[2][0] = 0.0; modelView[2][1] = 0.0; modelView[2][2] = 1.0;

  gl_Position = projection_matrix * modelView * vec4(position, 1.0f);
  gl_Position.z = -1.0;
  v_uv = i_uv / textureSize(texture_image, 0).rg;
}")

(define-class-shader (debug-draw-text :fragment-shader)
  "in vec2 v_uv;
out vec4 color;
uniform sampler2D texture_image;

void main(){
  float fg_bg = texture(texture_image, v_uv, 0).r;
  color = mix(vec4(0,0,0,1), vec4(1,1,1,0.3), fg_bg);
}")

(defgeneric debug-draw (thing &key))

(define-shader-entity debug-draw (renderable standalone-shader-entity)
  ((name :initform 'debug-draw)
   (instances :accessor instances)
   (points-vao :accessor points-vao)
   (points :accessor points)
   (lines-vao :accessor lines-vao)
   (lines :accessor lines)
   (flats-vao :accessor flats-vao)
   (flats :accessor flats)
   (text-render :accessor text-render)
   (dirty :initform 0 :accessor dirty)
   (clear-after-render :initform T :initarg :clear-after-render :accessor clear-after-render)))

(defmethod initialize-instance :after ((draw debug-draw) &key)
  (setf (instances draw) (make-array 64 :fill-pointer 0 :adjustable T :element-type '(unsigned-byte 32)))
  (setf (points draw) (make-array 64 :fill-pointer 0 :adjustable T :element-type 'single-float))
  (let ((vbo (make-instance 'vertex-buffer :buffer-data (points draw))))
    (setf (points-vao draw) (make-instance 'vertex-array :vertex-form :points :bindings
                                           `((,vbo :offset  0 :stride 24)
                                             (,vbo :offset 12 :stride 24)))))
  (setf (lines draw) (make-array 128 :fill-pointer 0 :adjustable T :element-type 'single-float))
  (let ((vbo (make-instance 'vertex-buffer :buffer-data (lines draw))))
    (setf (lines-vao draw) (make-instance 'vertex-array :vertex-form :lines :bindings
                                          `((,vbo :offset  0 :stride 24)
                                            (,vbo :offset 12 :stride 24)))))
  (setf (flats draw) (make-array 128 :fill-pointer 0 :adjustable T :element-type 'single-float))
  (let ((vbo (make-instance 'vertex-buffer :buffer-data (flats draw))))
    (setf (flats-vao draw) (make-instance 'vertex-array :vertex-form :triangles :bindings
                                          `((,vbo :offset  0 :stride 24)
                                            (,vbo :offset 12 :stride 24)))))
  (setf (text-render draw) (make-instance 'debug-draw-text)))

(defmethod text-vao ((draw debug-draw))
  (text-vao (text-render draw)))

(defmethod text ((draw debug-draw))
  (text (text-render draw)))

(defmethod stage ((draw debug-draw) (area staging-area))
  (stage (points-vao draw) area)
  (stage (lines-vao draw) area)
  (stage (flats-vao draw) area)
  (stage (text-render draw) area))

(defmethod render :before ((draw debug-draw) target)
  (unless (allocated-p (shader-program draw))
    (commit draw (loader +main+) :unload NIL)))

(defmethod render ((draw debug-draw) (program shader-program))
  (when (logbitp 1 (dirty draw))
    (resize-buffer-data (caar (bindings (points-vao draw))) T))
  (when (logbitp 2 (dirty draw))
    (resize-buffer-data (caar (bindings (lines-vao draw))) T))
  (when (logbitp 3 (dirty draw))
    (resize-buffer-data (caar (bindings (text-vao draw))) T))
  (when (logbitp 4 (dirty draw))
    (resize-buffer-data (caar (bindings (flats-vao draw))) T))
  (setf (dirty draw) 0)
  (setf (uniform program "view_matrix") (view-matrix))
  (setf (uniform program "projection_matrix") (projection-matrix))
  (setf (uniform program "lighting") 0.0)
  (with-pushed-features
    (disable-feature :depth-test)
    (render-array (points-vao draw) :vertex-count (truncate (length (points draw)) 6))
    (render-array (lines-vao draw) :vertex-count (truncate (length (lines draw)) 6)))
  (setf (uniform program "lighting") 1.0)
  (render-array (flats-vao draw) :vertex-count (truncate (length (flats draw)) 6))
  (render (text-render draw) T)
  (let ((scene (scene draw)))
    (unless (eq draw (elt scene (1- (length scene))))
      #++(warn "~S is not the last entity in the scene" draw)
      (leave draw T)
      (enter draw scene)))
  (when (clear-after-render draw)
    (debug-clear :debug-draw draw)))

(defun debug-draw-allocate (data instances instance type n)
  (declare (type (vector (unsigned-byte 32)) instances))
  (declare (type (vector single-float) data))
  (cond (instance
         (let ((diff (- (* 3 n) (aref instances (+ 2 (* 3 instance)))))
               (i (aref instances (+ 1 (* 3 instance)))))
           (unless (= 0 diff)
             (array-utils:array-shift data :n diff :from i)
             (loop for inst from (* 3 instance) below (length instances) by 3
                   when (= type (aref instances inst))
                   do (incf (aref instances (1+ inst)) diff)))
           (values i instance)))
        (T
         (let ((i (length data)))
           (when (< (array-total-size data) (+ (length data) (* 3 n)))
             (adjust-array data (+ (length data) (* 3 n))))
           (incf (fill-pointer data) (* 3 n))
           (setf instance (truncate (length instances) 3))
           (vector-push-extend type instances 3)
           (vector-push i instances)
           (vector-push (* 3 n) instances)
           (values i instance)))))

(defun %debug-draw ()
  (or (node 'debug-draw T)
      (enter-and-load (make-instance 'debug-draw) (scene +main+) +main+)))

(defmacro define-debug-draw-function ((name type) args &body body)
  (let ((type-id (ecase type (points 1) (lines 2) (text 3) (flats 4))))
    `(defun ,name (,@args (debug-draw (node 'debug-draw T)) (container (scene +main+)) instance)
       (flet ((,name ()
                (unless debug-draw
                  (setf debug-draw (enter-and-load (make-instance 'debug-draw) container +main+)))
                (let* ((data (,type debug-draw))
                       (instances (instances debug-draw))
                       (i 0))
                  (declare (type (vector single-float) data))
                  (declare (type (vector (unsigned-byte 32)) instances))
                  (declare (type (unsigned-byte 32) i))
                  (flet ((v (v)
                           (setf (aref data (+ 0 i)) (vx v))
                           (setf (aref data (+ 1 i)) (vy v))
                           (setf (aref data (+ 2 i)) (vz v))
                           (incf i 3))
                         (allocate (n)
                           (multiple-value-setq (i instance)
                             (debug-draw-allocate data instances instance ,type-id n))))
                    (declare (ignorable #'v))
                    ,@body))
                (setf (ldb (byte 1 ,type-id) (dirty debug-draw)) 1)
                instance))
         (if (current-p (context +main+))
             (,name)
             (with-eval-in-render-loop (T :block T)
               (,name)))))))

(defmethod debug-draw ((point vec2) &rest args &key &allow-other-keys)
  (apply #'debug-point (vxy_ point) args))

(defmethod debug-draw ((point vec3) &rest args &key &allow-other-keys)
  (apply #'debug-point point args))

(define-debug-draw-function (debug-point points) (point &key (color #.(vec 1 0 0)))
  (allocate 2)
  (v point)
  (v color))

(define-debug-draw-function (debug-line lines) (a b &key (color #.(vec 1 0 0)) (color-a color) (color-b color))
  (allocate 4)
  (v a)
  (v color-a)
  (v b)
  (v color-b))

(defmethod debug-draw ((tf transform) &key &allow-other-keys)
  (debug-orientation (tlocation tf) (trotation tf) :stretch (tscaling tf)))

(define-debug-draw-function (debug-orientation lines) (location orientation &key (stretch #.(vec3 1)))
  (allocate 12)
  (v location)
  (v #.(vec 1 0 0))
  (v (nv+ (q* orientation (vx__ stretch)) location))
  (v #.(vec 1 0 0))
  (v location)
  (v #.(vec 0 1 0))
  (v (nv+ (q* orientation (v_y_ stretch)) location))
  (v #.(vec 0 1 0))
  (v location)
  (v #.(vec 0 0 1))
  (v (nv+ (q* orientation (v__z stretch)) location))
  (v #.(vec 0 0 1)))

(define-debug-draw-function (debug-vector lines) (location direction &key (color #.(vec 1 0 0)) (length 2.0))
  (allocate 20)
  (let* ((end (vunit direction))
         (quat (qtowards +vy3+ end))
         (tmp (vec3)))
    (declare (dynamic-extent end tmp quat))
    (!v+* tmp location end (* -0.1 length))
    (!v+* end location end length)
    (v location) (v #.(vec3 0))
    (v end) (v color)
    (flet ((fin (axis phi)
             (let ((other (qfrom-angle axis phi)))
               (declare (dynamic-extent other))
               (!q* other other quat)
               (!q* tmp other +vy3+)
               (!v+* tmp end tmp (* -0.3 length))
               (v tmp) (v color)
               (v end) (v color))))
      (fin +vx3+ (* +0.5 F-PI/4))
      (fin +vz3+ (* +0.5 F-PI/4))
      (fin +vx3+ (* -0.5 F-PI/4))
      (fin +vz3+ (* -0.5 F-PI/4)))))

(defmethod debug-draw ((string string) &rest args &key &allow-other-keys)
  (let ((point (getf args :point)))
    (remf args :point)
    (apply #'debug-text (or point (vec 0 0 0)) string args)))

(define-debug-draw-function (debug-text text) (point text &key (scale 0.2))
  (allocate (* 5 2 (length text)))
  (print-ascii-text text data :start i
                              :adjust NIL
                              :x (vx point)
                              :y (vy point)
                              :z (if (typep point 'vec2) 0.0 (vz point))
                              :scale scale))

(defmethod debug-draw ((cache global-bounds-cache) &key (color #.(vec 1 0 0)) draw-obb draw-sphere)
  (when (global-bounds-cache-dirty-p cache)
    (update-global-bounds-cache cache))
  (when draw-obb
    (debug-box (global-bounds-cache-box-offset cache)
               (global-bounds-cache-obb cache)
               :color #.(vec 0 0 1) :transform (global-transform-matrix cache)))
  (when draw-sphere
    (debug-sphere (v+ (global-bounds-cache-location cache)
                      (global-bounds-cache-sphere-offset cache))
                  (global-bounds-cache-radius cache)
                  :color #.(vec 0 1 0) :transform #.(meye 4)))
  (debug-box (v+ (global-bounds-cache-location cache)
                 (global-bounds-cache-box-offset cache))
             (global-bounds-cache-aabb cache)
             :color color :transform #.(meye 4)))

(defmethod debug-draw ((primitive box) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (apply #'debug-box #.(vec 0 0 0) (box-bsize primitive) args))

(define-debug-draw-function (debug-box lines) (location bsize &key (color #.(vec 1 0 0)) (transform (model-matrix)))
  (allocate (* 3 4 2 2))
  (flet ((line (a b)
           (v (n*m transform (v+ location a))) (v color)
           (v (n*m transform (v+ location b))) (v color)))
    (let ((w (vx bsize)) (h (vy bsize)) (d (vz bsize)))
      (line (vec (- w) (- h) (- d)) (vec (+ w) (- h) (- d)))
      (line (vec (+ w) (- h) (- d)) (vec (+ w) (+ h) (- d)))
      (line (vec (+ w) (+ h) (- d)) (vec (- w) (+ h) (- d)))
      (line (vec (- w) (+ h) (- d)) (vec (- w) (- h) (- d)))

      (line (vec (- w) (- h) (+ d)) (vec (+ w) (- h) (+ d)))
      (line (vec (+ w) (- h) (+ d)) (vec (+ w) (+ h) (+ d)))
      (line (vec (+ w) (+ h) (+ d)) (vec (- w) (+ h) (+ d)))
      (line (vec (- w) (+ h) (+ d)) (vec (- w) (- h) (+ d)))

      (line (vec (- w) (- h) (- d)) (vec (- w) (- h) (+ d)))
      (line (vec (+ w) (- h) (- d)) (vec (+ w) (- h) (+ d)))
      (line (vec (+ w) (+ h) (- d)) (vec (+ w) (+ h) (+ d)))
      (line (vec (- w) (+ h) (- d)) (vec (- w) (+ h) (+ d))))))

(defmethod debug-draw ((primitive sphere) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (apply #'debug-sphere #.(vec 0 0 0) (sphere-radius primitive) args))

(define-debug-draw-function (debug-sphere lines) (location radius &key (color #.(vec 1 0 0)) (segments 16) (transform (model-matrix)))
  (allocate (* 3 (1+ segments) 2 2))
  (labels ((line (a b)
             (v (n*m transform (nv+ a location))) (v color)
             (v (n*m transform (nv+ b location))) (v color))
           (circle (coerce)
             (loop for i from 0 to segments
                   for rad-1 = (* F-2PI (/ (+ i 0) segments))
                   for rad-2 = (* F-2PI (/ (+ i 1) segments))
                   do (line (funcall coerce (vec (* radius (cos rad-1)) (* radius (sin rad-1))))
                            (funcall coerce (vec (* radius (cos rad-2)) (* radius (sin rad-2))))))))
    (circle #'vxy_)
    (circle #'vx_y)
    (circle #'v_xy)))

(defmethod debug-draw ((primitive ellipsoid) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (apply #'debug-ellipsoid #.(vec 0 0 0) (ellipsoid-radius primitive) args))

(define-debug-draw-function (debug-ellipsoid lines) (location radius &key (color #.(vec 1 0 0)) (segments 16) (transform (model-matrix)))
  (allocate (* 3 (1+ segments) 2 2))
  (labels ((line (a b)
             (v (n*m transform (nv+ a location))) (v color)
             (v (n*m transform (nv+ b location))) (v color))
           (circle (coerce)
             (loop for i from 0 to segments
                   for rad-1 = (* F-2PI (/ (+ i 0) segments))
                   for rad-2 = (* F-2PI (/ (+ i 1) segments))
                   do (line (funcall coerce (cos rad-1) (sin rad-1))
                            (funcall coerce (cos rad-2) (sin rad-2))))))
    (circle (lambda (a b) (vec (* (vx radius) a) (* (vy radius) b) 0)))
    (circle (lambda (a b) (vec (* (vx radius) a) 0 (* (vz radius) b))))
    (circle (lambda (a b) (vec 0 (* (vy radius) a) (* (vz radius) b))))))

(defmethod debug-draw ((primitive cylinder) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (apply #'debug-cylinder #.(vec 0 0 0) (cylinder-radius primitive) (cylinder-height primitive) args))

(define-debug-draw-function (debug-cylinder lines) (location radius height &key (color #.(vec 1 0 0)) (segments 16) (transform (model-matrix)))
  (allocate (+ (* 2 (1+ segments) 2 2) (* 4 2 2 2)))
  (labels ((line (a b)
             (v (n*m transform (nv+ a location))) (v color)
             (v (n*m transform (nv+ b location))) (v color))
           (circle (y)
             (loop for i from 0 below segments
                   for rad-1 = (* F-2PI (/ (+ i 0) segments))
                   for rad-2 = (* F-2PI (/ (+ i 1) segments))
                   do (line (vec (* radius (cos rad-1)) y (* radius (sin rad-1)))
                            (vec (* radius (cos rad-2)) y (* radius (sin rad-2)))))))
    (circle (+ height))
    (circle (- height))
    (line (vec (- radius) (- height) 0.0) (vec (- radius) (+ height) 0.0))
    (line (vec (+ radius) (- height) 0.0) (vec (+ radius) (+ height) 0.0))
    (line (vec 0.0 (- height) (- radius)) (vec 0.0 (+ height) (- radius)))
    (line (vec 0.0 (- height) (+ radius)) (vec 0.0 (+ height) (+ radius)))))

(defmethod debug-draw ((primitive cone) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (apply #'debug-cone #.(vec 0 0 0) (cone-radius primitive) (cone-height primitive) args))

(define-debug-draw-function (debug-cone lines) (location radius height &key (color #.(vec 1 0 0)) (segments 16) (transform (model-matrix)))
  (allocate (+ (* (1+ segments) 2 2) (* 4 2 2 2)))
  (labels ((line (a b)
             (v (n*m transform (nv+ a location))) (v color)
             (v (n*m transform (nv+ b location))) (v color))
           (circle (y)
             (loop for i from 0 below segments
                   for rad-1 = (* F-2PI (/ (+ i 0) segments))
                   for rad-2 = (* F-2PI (/ (+ i 1) segments))
                   do (line (vec (* radius (cos rad-1)) y (* radius (sin rad-1)))
                            (vec (* radius (cos rad-2)) y (* radius (sin rad-2)))))))
    (circle (- height))
    (line (vec (- radius) (- height) 0.0) (vec 0.0 (+ height) 0.0))
    (line (vec (+ radius) (- height) 0.0) (vec 0.0 (+ height) 0.0))
    (line (vec 0.0 (- height) (- radius)) (vec 0.0 (+ height) 0.0))
    (line (vec 0.0 (- height) (+ radius)) (vec 0.0 (+ height) 0.0))))

(defmethod debug-draw ((primitive pill) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (apply #'debug-pill #.(vec 0 0 0) (pill-radius primitive) (pill-height primitive) args))

(define-debug-draw-function (debug-pill lines) (location radius height &key (color #.(vec 1 0 0)) (segments 16) (transform (model-matrix)))
  (allocate (+ (* 2 (1+ segments) 2 2) (* 4 2 2 2) (* 2 segments 2 2)))
  (labels ((line (a b)
             (v (n*m transform (nv+ a location))) (v color)
             (v (n*m transform (nv+ b location))) (v color))
           (circle (y)
             (loop for i from 0 below segments
                   for rad-1 = (* F-2PI (/ (+ i 0) segments))
                   for rad-2 = (* F-2PI (/ (+ i 1) segments))
                   do (line (vec (* radius (cos rad-1)) y (* radius (sin rad-1)))
                            (vec (* radius (cos rad-2)) y (* radius (sin rad-2))))))
           (semicircle (y coerce start)
             (loop for i from start below (+ start (truncate segments 2))
                   for rad-1 = (* F-2PI (/ (+ i 0) segments))
                   for rad-2 = (* F-2PI (/ (+ i 1) segments))
                   do (line (nv+ (funcall coerce (vec (* radius (cos rad-1)) (* radius (sin rad-1)))) (vec 0 y 0))
                            (nv+ (funcall coerce (vec (* radius (cos rad-2)) (* radius (sin rad-2)))) (vec 0 y 0))))))
    (circle (+ height))
    (circle (- height))
    (semicircle (+ height) #'vxy_ 0)
    (semicircle (- height) #'vxy_ (* segments 2/4))
    (semicircle (+ height) #'v_xy (* segments 3/4))
    (semicircle (- height) #'v_xy (* segments 1/4))
    (line (vec (- radius) (- height) 0.0) (vec (- radius) (+ height) 0.0))
    (line (vec (+ radius) (- height) 0.0) (vec (+ radius) (+ height) 0.0))
    (line (vec 0.0 (- height) (- radius)) (vec 0.0 (+ height) (- radius)))
    (line (vec 0.0 (- height) (+ radius)) (vec 0.0 (+ height) (+ radius)))))

(defmethod debug-draw ((primitive triangle) &rest args &key &allow-other-keys)
  (let ((verts (make-array 9 :element-type 'single-float))
        (faces (make-array 3 :element-type '(unsigned-byte 32) :initial-contents '(0 1 2))))
    (declare (dynamic-extent verts faces))
    (setf (aref verts 0) (vx (triangle-a primitive)))
    (setf (aref verts 1) (vy (triangle-a primitive)))
    (setf (aref verts 2) (vz (triangle-a primitive)))
    (setf (aref verts 3) (vx (triangle-b primitive)))
    (setf (aref verts 4) (vy (triangle-b primitive)))
    (setf (aref verts 5) (vz (triangle-b primitive)))
    (setf (aref verts 6) (vx (triangle-c primitive)))
    (setf (aref verts 7) (vy (triangle-c primitive)))
    (setf (aref verts 8) (vz (triangle-c primitive)))
    (apply #'debug-triangles verts faces args)))

(defmethod debug-draw ((entity vertex-entity) &rest args &key &allow-other-keys)
  (apply #'debug-vertex-array (vertex-array entity) args))

(defmethod debug-draw ((array vertex-array) &rest args &key &allow-other-keys)
  (apply #'debug-vertex-array array args))

(defmethod debug-draw :around ((entity transformed-entity) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (tmat (tf entity))))
  (apply #'call-next-method entity args))

(defmethod debug-draw ((data mesh-data) &rest args &key &allow-other-keys)
  (apply #'debug-triangles (reordered-vertex-data data '(location)) (faces data) args))

(defmethod debug-draw ((primitive general-mesh) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (apply #'debug-triangles (general-mesh-vertices primitive) (general-mesh-faces primitive) args))

(defmethod debug-draw ((primitive primitive) &rest args &key &allow-other-keys)
  (unless (getf args :transform)
    (setf (getf args :transform) (primitive-transform primitive)))
  (let ((primitive (coerce-object primitive 'convex-mesh)))
    (apply #'debug-triangles (general-mesh-vertices primitive) (general-mesh-faces primitive) args)))

(defmethod debug-draw ((entity multi-mesh-entity) &rest args &key &allow-other-keys)
  (loop for vao across (vertex-arrays entity)
        do (apply #'debug-draw vao args)))

(defun debug-triangles (vertices faces &rest args &key flats &allow-other-keys)
  (remf args :flats)
  (apply (if flats #'debug-triangle-flats #'debug-triangle-lines)
         vertices faces args))

(define-debug-draw-function (debug-triangle-lines lines) (vertices faces &key (color #.(vec 1 0 0)) (transform (model-matrix)))
  (allocate (* (length faces) 2 2))
  (flet ((lines (vec)
           (v vec)
           (v color)))
    (loop with prev
          for e across faces
          for c = 0 then (mod (1+ c) 3)
          for i = (* e 3)
          do (let ((vec (vec (aref vertices (+ 0 i)) (aref vertices (+ 1 i)) (aref vertices (+ 2 i)) 1.0)))
               (declare (dynamic-extent vec))
               (n*m transform vec)
               (case c
                 (0 (lines vec)
                  (setf prev vec))
                 (1 (lines vec)
                  (lines vec))
                 (T (lines vec)
                  (lines prev)
                  (lines vec)))))))

(define-debug-draw-function (debug-triangle-flats flats) (vertices faces &key (color #.(vec 1 0 0)) (transform (model-matrix)))
  (allocate (* (length faces) 2))
  (loop for e across faces
        for i = (* e 3)
        do (let ((vec (vec (aref vertices (+ 0 i)) (aref vertices (+ 1 i)) (aref vertices (+ 2 i)) 1.0)))
             (declare (dynamic-extent vec))
             (n*m transform vec)
             (v vec)
             (v color))))

(defmethod debug-draw ((camera camera) &rest args &key &allow-other-keys)
  (apply #'debug-matrix (m* *projection-matrix* *view-matrix*) args))

(define-debug-draw-function (debug-matrix lines) (matrix &key (color #.(vec 1 0 0)))
  (declare (type mat4 matrix))
  (let ((a #.(vec -1 -1 -1)) (b #.(vec +1 -1 -1)) (c #.(vec +1 +1 -1)) (d #.(vec -1 +1 -1))
        (x #.(vec -1 -1 +1)) (y #.(vec +1 -1 +1)) (z #.(vec +1 +1 +1)) (w #.(vec -1 +1 +1))
        (inv (minv matrix)) (tmp (vec4)))
    (declare (dynamic-extent inv tmp))
    (with-fast-matref (m inv)
      (labels ((invert (v)
                 (let ((w (/ (+ (* (vx v) (m 3 0)) (* (vy v) (m 3 1)) (* (vz v) (m 3 2)) (m 3 3)))))
                   (n*m inv (vsetf tmp (* (vx v) w) (* (vy v) w) (* (vz v) w) w))))
               (line (a b)
                 (v (invert a))
                 (v color)
                 (v (invert b))
                 (v color)))
        (allocate (* 4 4 3))
        (line a b) (line b c) (line c d) (line d a)
        (line x y) (line y z) (line z w) (line w x)
        (line a x) (line b y) (line c z) (line d w)))))

(defun debug-vertex-array (vao &rest args &key flats &allow-other-keys)
  (remf args :flats)
  (apply (if flats #'debug-vertex-array-flats #'debug-vertex-array-lines)
         vao args))

(define-debug-draw-function (debug-vertex-array-lines lines) (vao &key (color #.(vec 1 0 0)) (transform (model-matrix)))
  (let ((count 0) prev pprev)
    (labels ((lines (vec)
               (v vec)
               (v color))
             (line-strip (vec)
               (case count
                 (0 (lines vec)
                  (setf count 1))
                 (1 (lines vec)
                  (lines vec))))
             (line-loop (vec)
               (declare (ignore vec))
               (implement!))
             (triangles (vec)
               (case count
                 (0 (lines vec)
                  (setf prev vec)
                  (setf count 1))
                 (1 (lines vec)
                  (lines vec)
                  (setf count 2))
                 (T (lines vec)
                  (lines prev)
                  (lines vec)
                  (setf count 0))))
             (triangle-strip (vec)
               (case count
                 (0 (lines vec)
                  (setf pprev vec)
                  (setf count 1))
                 (1 (lines vec)
                  (setf prev vec)
                  (setf count 2))
                 (T (lines vec)
                  (lines prev)
                  (lines vec)
                  (lines pprev)
                  (shiftf pprev prev vec))))
             (triangle-fan (vec)
               (case count
                 (0 (lines prev)
                  (setf pprev vec)
                  (setf count 1))
                 (1 (lines vec)
                  (setf prev vec)
                  (setf count 2))
                 (T (lines vec)
                  (lines prev)
                  (lines vec)
                  (lines pprev)
                  (setf prev vec))))
             (alloc (verts)
               (ecase (vertex-form vao)
                 (:lines (allocate (* 2 verts)))
                 (:line-strip (allocate (* 2 2 (1- verts))))
                 (:line-loop (allocate (* 2 2 verts)))
                 (:triangles (allocate (* 2 2 verts)))
                 (:triangle-strip (allocate (* 2 2 (1+ (* 2 (- verts 2))))))
                 (:triangle-fan (allocate (* 2 2 (1+ (* 2 (- verts 2)))))))))
      (let ((vertex (ecase (vertex-form vao)
                      (:lines #'lines)
                      (:line-strip #'line-strip)
                      (:line-loop #'line-loop)
                      (:triangles #'triangles)
                      (:triangle-strip #'triangle-strip)
                      (:triangle-fan #'triangle-fan)))
            ebo vbo)
        (loop for binding in (bindings vao)
              do (case (buffer-type (unlist binding))
                   (:element-array-buffer
                    (setf ebo (buffer-data (unlist binding))))
                   (:array-buffer
                    (when (= 0 (getf (rest binding) :index 0))
                      (setf vbo binding)))))
        (destructuring-bind (buffer &key (size 3) (stride 0) (offset 0) &allow-other-keys) vbo
          (let ((data (buffer-data buffer)))
            (cond (ebo
                   (alloc (length ebo))
                   (loop for e across ebo
                         for i = (+ (floor offset 4) (* (floor stride 4) e))
                         do (ecase size
                              (3
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) (aref data (+ 2 i)) 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec)))
                              (2
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) 0.0 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec))))))
                  (T
                   (alloc (truncate (- (length data) (floor offset 4)) (floor stride 4)))
                   (loop for i from (floor offset 4) by (floor stride 4) below (length data)
                         do (ecase size
                              (3
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) (aref data (+ 2 i)) 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec)))
                              (2
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) 0.0 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec)))))))))))))

(define-debug-draw-function (debug-vertex-array-flats flats) (vao &key (color #.(vec 1 0 0)) (transform (model-matrix)))
  (let ((count 0) prev pprev)
    (labels ((triangles (vec)
               (v vec) (v color))
             (triangle-strip (vec)
               (case count
                 (0 (triangles vec)
                  (setf count 1))
                 (1 (triangles vec)
                  (setf prev vec)
                  (setf count 2))
                 (T (triangles vec)
                  (triangles prev)
                  (triangles vec)
                  (shiftf pprev prev vec))))
             (triangle-fan (vec)
               (case count
                 (0 (triangles vec)
                  (setf pprev vec)
                  (setf count 1))
                 (1 (triangles vec)
                  (setf prev vec)
                  (setf count 2))
                 (T (triangles vec)
                  (triangles pprev)
                  (triangles vec)
                  (setf prev vec))))
             (alloc (verts)
               (ecase (vertex-form vao)
                 (:triangles (allocate (* 2 verts)))
                 (:triangle-strip (allocate (* 2 (1+ (* 2 (- verts 2))))))
                 (:triangle-fan (allocate (* 2 (1+ (* 2 (- verts 2)))))))))
      (let ((vertex (ecase (vertex-form vao)
                      (:triangles #'triangles)
                      (:triangle-strip #'triangle-strip)
                      (:triangle-fan #'triangle-fan)))
            ebo vbo)
        (loop for binding in (bindings vao)
              do (case (buffer-type (unlist binding))
                   (:element-array-buffer
                    (setf ebo (buffer-data (unlist binding))))
                   (:array-buffer
                    (when (= 0 (getf (rest binding) :index 0))
                      (setf vbo binding)))))
        (destructuring-bind (buffer &key (size 3) (stride 0) (offset 0) &allow-other-keys) vbo
          (let ((data (buffer-data buffer)))
            (cond (ebo
                   (alloc (length ebo))
                   (loop for e across ebo
                         for i = (+ (floor offset 4) (* (floor stride 4) e))
                         do (ecase size
                              (3
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) (aref data (+ 2 i)) 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec)))
                              (2
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) 0.0 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec))))))
                  (T
                   (alloc (truncate (- (length data) (floor offset 4)) (floor stride 4)))
                   (loop for i from (floor offset 4) by (floor stride 4) below (length data)
                         do (ecase size
                              (3
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) (aref data (+ 2 i)) 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec)))
                              (2
                               (let ((vec (vec (aref data (+ 0 i)) (aref data (+ 1 i)) 0.0 1.0)))
                                 (declare (dynamic-extent vec))
                                 (n*m transform vec)
                                 (funcall vertex vec)))))))))))))

(defun debug-clear (&key (debug-draw (node 'debug-draw T)) instance)
  (when debug-draw
    (cond (instance
           (let* ((type (aref (instances debug-draw) (+ 0 (* 3 instance))))
                  (start (aref (instances debug-draw) (+ 1 (* 3 instance))))
                  (size (aref (instances debug-draw) (+ 2 (* 3 instance))))
                  (data (ecase type
                          (1 (points debug-draw))
                          (2 (lines debug-draw))
                          (3 (text debug-draw)))))
             (setf (ldb (byte 1 type) (dirty debug-draw)) 1)
             (array-utils:array-shift data :n size :from start)
             (when (< (* 3 (1+ instance)) (length (instances debug-draw)))
               (array-utils:array-shift (instances debug-draw) :n -3 :from (* 3 (1+ instance))))))
          (T
           (setf (fill-pointer (points debug-draw)) 0)
           (setf (fill-pointer (lines debug-draw)) 0)
           (setf (fill-pointer (flats debug-draw)) 0)
           (setf (fill-pointer (text debug-draw)) 0)
           (setf (fill-pointer (instances debug-draw)) 0)
           (setf (dirty debug-draw) (1- (ash 1 32)))))))

(define-class-shader (debug-draw :vertex-shader)
  "layout (location = 0) in vec3 position;
layout (location = 1) in vec3 i_color;
out vec3 v_color;
out vec3 view;
out vec3 light;

uniform mat4 view_matrix;
uniform mat4 projection_matrix;

void main(){
  view = (view_matrix * vec4(position, 1)).xyz;
  light = vec3(0, 0, -1);
  gl_Position = projection_matrix * vec4(view, 1);
  v_color = i_color;
}")

(define-class-shader (debug-draw :fragment-shader)
  "in vec3 v_color;
in vec3 view;
in vec3 light;
out vec4 color;
uniform float lighting = 0.0;

void main(){
  // We derive the normal here in order to get per-face flat shading.
  vec3 normal = normalize(cross(dFdx(view), dFdy(view)));
  // Basic phong lighting using view-space calculations.
  float diffuse = dot(normal, -light);
  float specular =  clamp(pow(max(dot(vec3(0,0,1), reflect(light, normal)), 0.0), 32), 0.0, 0.5);
  float light = mix(1.0, clamp(diffuse*0.7 + 0.2, 0.2, 0.9), lighting);
  color = vec4(v_color * light + (specular * lighting), 1);
}")