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#|
This file is a part of trial
(c) 2019 Shirakumo http://tymoon.eu (shinmera@tymoon.eu)
Author: Nicolas Hafner <shinmera@tymoon.eu>
|#
(in-package #:org.shirakumo.fraf.trial)
(define-gl-struct (particle (:layout-standard :vertex-buffer))
(lifetime :vec2 :accessor lifetime))
(define-shader-subject particle-emitter ()
((live-particles :initform 0 :accessor live-particles)
(vertex-array :accessor vertex-array)
(particle-buffer :initarg :particle-buffer :accessor particle-buffer)))
(defmethod initialize-instance :after ((emitter particle-emitter) &key particle-mesh particle-buffer)
(setf (vertex-array emitter)
(add-vertex-bindings
particle-buffer
(change-class particle-mesh 'vertex-array))))
(defmethod paint ((emitter particle-emitter) pass)
(let ((vao (vertex-array emitter)))
(gl:bind-vertex-array (gl-name vao))
(%gl:draw-elements-instanced (vertex-form vao) (size vao) :unsigned-int 0 (live-particles emitter))))
(defgeneric initial-particle-state (emitter tick particle))
(defgeneric update-particle-state (emitter tick input output))
(defgeneric new-particle-count (emitter tick)) ; => N
(define-handler (particle-emitter tick) (ev)
(let ((vbo (particle-buffer particle-emitter))
(write-offset 0))
(let ((data (struct-vector vbo)))
(declare (type simple-vector data))
(loop for read-offset from 0 below (live-particles particle-emitter)
for particle = (aref data read-offset)
do (when (< (vx2 (lifetime particle)) (vy2 (lifetime particle)))
(when (update-particle-state particle-emitter ev particle (aref data write-offset))
(incf write-offset))))
(loop repeat (new-particle-count particle-emitter ev)
while (< write-offset (length data))
do (initial-particle-state particle-emitter ev (aref data write-offset))
(incf write-offset))
(setf (live-particles particle-emitter) write-offset)
(update-buffer-data vbo T))))
(define-gl-struct (simple-particle (:include particle)
(:layout-standard :vertex-buffer))
(location :vec3 :accessor location)
(velocity :vec3 :accessor velocity))
(define-shader-subject simple-particle-emitter (particle-emitter)
())
(defmethod initial-particle-state :before ((emitter simple-particle-emitter) tick particle)
(setf (location particle) (vec 0 0 0)))
(defmethod update-particle-state ((emitter simple-particle-emitter) tick particle output)
(setf (location output) (v+ (location particle) (velocity particle)))
(let ((life (lifetime particle)))
(incf (vx2 life) (dt tick))
(setf (lifetime output) life)
(< (vx2 life) (vy2 life))))
(defmethod paint :before ((emitter simple-particle-emitter) (pass shader-pass))
(let ((program (shader-program-for-pass pass emitter)))
(setf (uniform program "view_matrix") (view-matrix))
(setf (uniform program "projection_matrix") (projection-matrix))
(setf (uniform program "model_matrix") (model-matrix))))
(define-class-shader (simple-particle-emitter :vertex-shader)
"layout (location = 0) in vec3 vtx_location;
uniform mat4 model_matrix;
uniform mat4 view_matrix;
uniform mat4 projection_matrix;
void main(){
vec3 position = vtx_location + location;
gl_Position = projection_matrix * view_matrix * model_matrix * vec4(position, 1.0f);
}")
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