text: /*
   * GStreamer
   * Copyright (C) 2014 Lubosz Sarnecki <lubosz@gmail.com>
   * Copyright (C) 2016 Matthew Waters <matthew@centricular.com>
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Library General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Library General Public License for more details.
   *
   * You should have received a copy of the GNU Library General Public
   * License along with this library; if not, write to the
   * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
   * Boston, MA 02110-1301, USA.
   */
  
  /**
   * SECTION:element-gltransformation
   * @title: gltransformation
   *
   * Transforms video on the GPU.
   *
   * ## Examples
   * |[
   * gst-launch-1.0 gltestsrc ! gltransformation rotation-z=45 ! glimagesink
   * ]| A pipeline to rotate by 45 degrees
   * |[
   * gst-launch-1.0 gltestsrc ! gltransformation translation-x=0.5 ! glimagesink
   * ]| Translate the video by 0.5
   * |[
   * gst-launch-1.0 gltestsrc ! gltransformation scale-y=0.5 scale-x=0.5 ! glimagesink
   * ]| Resize the video by 0.5
   * |[
   * gst-launch-1.0 gltestsrc ! gltransformation rotation-x=-45 ortho=True ! glimagesink
   * ]| Rotate the video around the X-Axis by -45° with an orthographic projection
   *
   */
  
  #ifdef HAVE_CONFIG_H
  #include "config.h"
  #endif
  
  #include "gstgltransformation.h"
  
  #include <gst/gl/gstglapi.h>
  #include <graphene-gobject.h>
  #include "gstglutils.h"
  
  #define GST_CAT_DEFAULT gst_gl_transformation_debug
  GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
  
  #define gst_gl_transformation_parent_class parent_class
  
  #define VEC4_FORMAT "%f,%f,%f,%f"
  #define VEC4_ARGS(v) graphene_vec4_get_x (v), graphene_vec4_get_y (v), graphene_vec4_get_z (v), graphene_vec4_get_w (v)
  #define VEC3_FORMAT "%f,%f,%f"
  #define VEC3_ARGS(v) graphene_vec3_get_x (v), graphene_vec3_get_y (v), graphene_vec3_get_z (v)
  #define VEC2_FORMAT "%f,%f"
  #define VEC2_ARGS(v) graphene_vec2_get_x (v), graphene_vec2_get_y (v)
  #define POINT3D_FORMAT "%f,%f,%f"
  #define POINT3D_ARGS(p) (p)->x, (p)->y, (p)->z
  
  enum
  {
    PROP_0,
    PROP_FOV,
    PROP_ORTHO,
    PROP_TRANSLATION_X,
    PROP_TRANSLATION_Y,
    PROP_TRANSLATION_Z,
    PROP_ROTATION_X,
    PROP_ROTATION_Y,
    PROP_ROTATION_Z,
    PROP_SCALE_X,
    PROP_SCALE_Y,
    PROP_MVP,
    PROP_PIVOT_X,
    PROP_PIVOT_Y,
    PROP_PIVOT_Z,
  };
  
  #define DEBUG_INIT \
      GST_DEBUG_CATEGORY_INIT (gst_gl_transformation_debug, "gltransformation", 0, "gltransformation element");
  
  G_DEFINE_TYPE_WITH_CODE (GstGLTransformation, gst_gl_transformation,
      GST_TYPE_GL_FILTER, DEBUG_INIT);
  
  static void gst_gl_transformation_set_property (GObject * object, guint prop_id,
      const GValue * value, GParamSpec * pspec);
  static void gst_gl_transformation_get_property (GObject * object, guint prop_id,
      GValue * value, GParamSpec * pspec);
  
  static gboolean gst_gl_transformation_set_caps (GstGLFilter * filter,
      GstCaps * incaps, GstCaps * outcaps);
  static gboolean gst_gl_transformation_src_event (GstBaseTransform * trans,
      GstEvent * event);
  static gboolean gst_gl_transformation_filter_meta (GstBaseTransform * trans,
      GstQuery * query, GType api, const GstStructure * params);
  static gboolean gst_gl_transformation_decide_allocation (GstBaseTransform *
      trans, GstQuery * query);
  
  static void gst_gl_transformation_gl_stop (GstGLBaseFilter * filter);
  static gboolean gst_gl_transformation_gl_start (GstGLBaseFilter * base_filter);
  static gboolean gst_gl_transformation_callback (gpointer stuff);
  static void gst_gl_transformation_build_mvp (GstGLTransformation *
      transformation);
  
  static GstFlowReturn
  gst_gl_transformation_prepare_output_buffer (GstBaseTransform * trans,
      GstBuffer * inbuf, GstBuffer ** outbuf);
  static gboolean gst_gl_transformation_filter (GstGLFilter * filter,
      GstBuffer * inbuf, GstBuffer * outbuf);
  static gboolean gst_gl_transformation_filter_texture (GstGLFilter * filter,
      GstGLMemory * in_tex, GstGLMemory * out_tex);
  
  static void
  gst_gl_transformation_class_init (GstGLTransformationClass * klass)
  {
    GObjectClass *gobject_class;
    GstElementClass *element_class;
    GstBaseTransformClass *base_transform_class;
  
    gobject_class = (GObjectClass *) klass;
    element_class = GST_ELEMENT_CLASS (klass);
    base_transform_class = GST_BASE_TRANSFORM_CLASS (klass);
  
    gst_gl_filter_add_rgba_pad_templates (GST_GL_FILTER_CLASS (klass));
  
    gobject_class->set_property = gst_gl_transformation_set_property;
    gobject_class->get_property = gst_gl_transformation_get_property;
  
    base_transform_class->src_event = gst_gl_transformation_src_event;
    base_transform_class->decide_allocation =
        gst_gl_transformation_decide_allocation;
    base_transform_class->filter_meta = gst_gl_transformation_filter_meta;
  
    GST_GL_BASE_FILTER_CLASS (klass)->gl_start = gst_gl_transformation_gl_start;
    GST_GL_BASE_FILTER_CLASS (klass)->gl_stop = gst_gl_transformation_gl_stop;
  
    GST_GL_FILTER_CLASS (klass)->set_caps = gst_gl_transformation_set_caps;
    GST_GL_FILTER_CLASS (klass)->filter = gst_gl_transformation_filter;
    GST_GL_FILTER_CLASS (klass)->filter_texture =
        gst_gl_transformation_filter_texture;
    GST_BASE_TRANSFORM_CLASS (klass)->prepare_output_buffer =
        gst_gl_transformation_prepare_output_buffer;
  
    g_object_class_install_property (gobject_class, PROP_FOV,
        g_param_spec_float ("fov", "Fov", "Field of view angle in degrees",
            0.0, G_MAXFLOAT, 90.0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_ORTHO,
        g_param_spec_boolean ("ortho", "Orthographic",
            "Use orthographic projection", FALSE,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    /* Rotation */
    g_object_class_install_property (gobject_class, PROP_ROTATION_X,
        g_param_spec_float ("rotation-x", "X Rotation",
            "Rotates the video around the X-Axis in degrees.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_ROTATION_Y,
        g_param_spec_float ("rotation-y", "Y Rotation",
            "Rotates the video around the Y-Axis in degrees.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_ROTATION_Z,
        g_param_spec_float ("rotation-z", "Z Rotation",
            "Rotates the video around the Z-Axis in degrees.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    /* Translation */
    g_object_class_install_property (gobject_class, PROP_TRANSLATION_X,
        g_param_spec_float ("translation-x", "X Translation",
            "Translates the video at the X-Axis, in universal [0-1] coordinate.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_TRANSLATION_Y,
        g_param_spec_float ("translation-y", "Y Translation",
            "Translates the video at the Y-Axis, in universal [0-1] coordinate.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_TRANSLATION_Z,
        g_param_spec_float ("translation-z", "Z Translation",
            "Translates the video at the Z-Axis, in universal [0-1] coordinate.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    /* Scale */
    g_object_class_install_property (gobject_class, PROP_SCALE_X,
        g_param_spec_float ("scale-x", "X Scale",
            "Scale multiplier for the X-Axis.",
            -G_MAXFLOAT, G_MAXFLOAT, 1.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_SCALE_Y,
        g_param_spec_float ("scale-y", "Y Scale",
            "Scale multiplier for the Y-Axis.",
            -G_MAXFLOAT, G_MAXFLOAT, 1.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    /* Pivot */
    g_object_class_install_property (gobject_class, PROP_PIVOT_X,
        g_param_spec_float ("pivot-x", "X Pivot",
            "Rotation pivot point X coordinate, where 0 is the center,"
            " -1 the left border, +1 the right border and <-1, >1 outside.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_PIVOT_Y,
        g_param_spec_float ("pivot-y", "Y Pivot",
            "Rotation pivot point X coordinate, where 0 is the center,"
            " -1 the left border, +1 the right border and <-1, >1 outside.",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    g_object_class_install_property (gobject_class, PROP_PIVOT_Z,
        g_param_spec_float ("pivot-z", "Z Pivot",
            "Relevant for rotation in 3D space. You look into the negative Z axis direction",
            -G_MAXFLOAT, G_MAXFLOAT, 0.0,
            G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    /* MVP */
    g_object_class_install_property (gobject_class, PROP_MVP,
        g_param_spec_boxed ("mvp-matrix",
            "Modelview Projection Matrix",
            "The final Graphene 4x4 Matrix for transformation",
            GRAPHENE_TYPE_MATRIX, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  
    gst_element_class_set_metadata (element_class, "OpenGL transformation filter",
        "Filter/Effect/Video", "Transform video on the GPU",
        "Lubosz Sarnecki <lubosz@gmail.com>\n"
        "Matthew Waters <matthew@centricular.com>");
  
    GST_GL_BASE_FILTER_CLASS (klass)->supported_gl_api =
        GST_GL_API_OPENGL | GST_GL_API_OPENGL3 | GST_GL_API_GLES2;
  }
  
  static void
  gst_gl_transformation_init (GstGLTransformation * filter)
  {
    filter->shader = NULL;
    filter->fov = 90;
    filter->aspect = 1.0;
    filter->znear = 0.1f;
    filter->zfar = 100.0;
  
    filter->xscale = 1.0;
    filter->yscale = 1.0;
  
    filter->in_tex = 0;
  
    gst_gl_transformation_build_mvp (filter);
  }
  
  static void
  gst_gl_transformation_build_mvp (GstGLTransformation * transformation)
  {
    GstGLFilter *filter = GST_GL_FILTER (transformation);
    graphene_matrix_t modelview_matrix;
  
    if (!filter->out_info.finfo) {
      graphene_matrix_init_identity (&transformation->model_matrix);
      graphene_matrix_init_identity (&transformation->view_matrix);
      graphene_matrix_init_identity (&transformation->projection_matrix);
    } else {
      graphene_point3d_t translation_vector =
          GRAPHENE_POINT3D_INIT (transformation->xtranslation * 2.0 *
          transformation->aspect,
          transformation->ytranslation * 2.0,
          transformation->ztranslation * 2.0);
  
      graphene_point3d_t pivot_vector =
          GRAPHENE_POINT3D_INIT (-transformation->xpivot * transformation->aspect,
          transformation->ypivot,
          -transformation->zpivot);
  
      graphene_point3d_t negative_pivot_vector;
  
      graphene_vec3_t center;
      graphene_vec3_t up;
  
      gboolean current_passthrough;
      gboolean passthrough;
  
      graphene_vec3_init (&transformation->camera_position, 0.f, 0.f, 1.f);
      graphene_vec3_init (&center, 0.f, 0.f, 0.f);
      graphene_vec3_init (&up, 0.f, 1.f, 0.f);
  
      /* Translate into pivot origin */
      graphene_matrix_init_translate (&transformation->model_matrix,
          &pivot_vector);
  
      /* Scale */
      graphene_matrix_scale (&transformation->model_matrix,
          transformation->xscale, transformation->yscale, 1.0f);
  
      /* Rotation */
      graphene_matrix_rotate (&transformation->model_matrix,
          transformation->xrotation, graphene_vec3_x_axis ());
      graphene_matrix_rotate (&transformation->model_matrix,
          transformation->yrotation, graphene_vec3_y_axis ());
      graphene_matrix_rotate (&transformation->model_matrix,
          transformation->zrotation, graphene_vec3_z_axis ());
  
      /* Translate back from pivot origin */
      graphene_point3d_scale (&pivot_vector, -1.0, &negative_pivot_vector);
      graphene_matrix_translate (&transformation->model_matrix,
          &negative_pivot_vector);
  
      /* Translation */
      graphene_matrix_translate (&transformation->model_matrix,
          &translation_vector);
  
      if (transformation->ortho) {
        graphene_matrix_init_ortho (&transformation->projection_matrix,
            -transformation->aspect, transformation->aspect,
            -1, 1, transformation->znear, transformation->zfar);
      } else {
        graphene_matrix_init_perspective (&transformation->projection_matrix,
            transformation->fov,
            transformation->aspect, transformation->znear, transformation->zfar);
      }
  
      graphene_matrix_init_look_at (&transformation->view_matrix,
          &transformation->camera_position, &center, &up);
  
      current_passthrough =
          gst_base_transform_is_passthrough (GST_BASE_TRANSFORM (transformation));
      passthrough = transformation->xtranslation == 0.
          && transformation->ytranslation == 0.
          && transformation->ztranslation == 0. && transformation->xrotation == 0.
          && transformation->yrotation == 0. && transformation->zrotation == 0.
          && transformation->xscale == 1. && transformation->yscale == 1.
          && gst_video_info_is_equal (&filter->in_info, &filter->out_info);
      gst_base_transform_set_passthrough (GST_BASE_TRANSFORM (transformation),
          passthrough);
      if (current_passthrough != passthrough) {
        gst_base_transform_reconfigure_src (GST_BASE_TRANSFORM (transformation));
      }
    }
  
    graphene_matrix_multiply (&transformation->model_matrix,
        &transformation->view_matrix, &modelview_matrix);
    graphene_matrix_multiply (&modelview_matrix,
        &transformation->projection_matrix, &transformation->mvp_matrix);
  
    graphene_matrix_inverse (&transformation->model_matrix,
        &transformation->inv_model_matrix);
    graphene_matrix_inverse (&transformation->view_matrix,
        &transformation->inv_view_matrix);
    graphene_matrix_inverse (&transformation->projection_matrix,
        &transformation->inv_projection_matrix);
  }
  
  static void
  gst_gl_transformation_set_property (GObject * object, guint prop_id,
      const GValue * value, GParamSpec * pspec)
  {
    GstGLTransformation *filter = GST_GL_TRANSFORMATION (object);
  
    switch (prop_id) {
      case PROP_FOV:
        filter->fov = g_value_get_float (value);
        break;
      case PROP_ORTHO:
        filter->ortho = g_value_get_boolean (value);
        break;
      case PROP_TRANSLATION_X:
        filter->xtranslation = g_value_get_float (value);
        break;
      case PROP_TRANSLATION_Y:
        filter->ytranslation = g_value_get_float (value);
        break;
      case PROP_TRANSLATION_Z:
        filter->ztranslation = g_value_get_float (value);
        break;
      case PROP_ROTATION_X:
        filter->xrotation = g_value_get_float (value);
        break;
      case PROP_ROTATION_Y:
        filter->yrotation = g_value_get_float (value);
        break;
      case PROP_ROTATION_Z:
        filter->zrotation = g_value_get_float (value);
        break;
      case PROP_SCALE_X:
        filter->xscale = g_value_get_float (value);
        break;
      case PROP_SCALE_Y:
        filter->yscale = g_value_get_float (value);
        break;
      case PROP_PIVOT_X:
        filter->xpivot = g_value_get_float (value);
        break;
      case PROP_PIVOT_Y:
        filter->ypivot = g_value_get_float (value);
        break;
      case PROP_PIVOT_Z:
        filter->zpivot = g_value_get_float (value);
        break;
      default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
        break;
    }
    gst_gl_transformation_build_mvp (filter);
  }
  
  static void
  gst_gl_transformation_get_property (GObject * object, guint prop_id,
      GValue * value, GParamSpec * pspec)
  {
    GstGLTransformation *filter = GST_GL_TRANSFORMATION (object);
  
    switch (prop_id) {
      case PROP_FOV:
        g_value_set_float (value, filter->fov);
        break;
      case PROP_ORTHO:
        g_value_set_boolean (value, filter->ortho);
        break;
      case PROP_TRANSLATION_X:
        g_value_set_float (value, filter->xtranslation);
        break;
      case PROP_TRANSLATION_Y:
        g_value_set_float (value, filter->ytranslation);
        break;
      case PROP_TRANSLATION_Z:
        g_value_set_float (value, filter->ztranslation);
        break;
      case PROP_ROTATION_X:
        g_value_set_float (value, filter->xrotation);
        break;
      case PROP_ROTATION_Y:
        g_value_set_float (value, filter->yrotation);
        break;
      case PROP_ROTATION_Z:
        g_value_set_float (value, filter->zrotation);
        break;
      case PROP_SCALE_X:
        g_value_set_float (value, filter->xscale);
        break;
      case PROP_SCALE_Y:
        g_value_set_float (value, filter->yscale);
        break;
      case PROP_PIVOT_X:
        g_value_set_float (value, filter->xpivot);
        break;
      case PROP_PIVOT_Y:
        g_value_set_float (value, filter->ypivot);
        break;
      case PROP_PIVOT_Z:
        g_value_set_float (value, filter->zpivot);
        break;
      case PROP_MVP:
        /* FIXME: need to decompose this to support navigation events */
        g_value_set_boxed (value, (gconstpointer) & filter->mvp_matrix);
        break;
      default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
        break;
    }
  }
  
  static gboolean
  gst_gl_transformation_set_caps (GstGLFilter * filter, GstCaps * incaps,
      GstCaps * outcaps)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (filter);
  
    transformation->aspect =
        (gdouble) GST_VIDEO_INFO_WIDTH (&filter->out_info) /
        (gdouble) GST_VIDEO_INFO_HEIGHT (&filter->out_info);
  
    transformation->caps_change = TRUE;
  
    gst_gl_transformation_build_mvp (transformation);
  
    return TRUE;
  }
  
  static void
  _intersect_plane_and_ray (graphene_plane_t * video_plane, graphene_ray_t * ray,
      graphene_point3d_t * result)
  {
    float t = graphene_ray_get_distance_to_plane (ray, video_plane);
    GST_TRACE ("Calculated a distance of %f to the plane", t);
    graphene_ray_get_position_at (ray, t, result);
  }
  
  static void
  _screen_coord_to_world_ray (GstGLTransformation * transformation, float x,
      float y, graphene_ray_t * ray)
  {
    GstGLFilter *filter = GST_GL_FILTER (transformation);
    gfloat w = (gfloat) GST_VIDEO_INFO_WIDTH (&filter->in_info);
    gfloat h = (gfloat) GST_VIDEO_INFO_HEIGHT (&filter->in_info);
    graphene_vec3_t ray_eye_vec3, ray_world_dir, *ray_origin, *ray_direction;
    graphene_vec3_t ray_ortho_dir;
    graphene_point3d_t ray_clip, ray_eye;
    graphene_vec2_t screen_coord;
  
    /* GL is y-flipped. i.e. 0, 0 is the bottom left corner in screen space */
    graphene_vec2_init (&screen_coord, (2. * x / w - 1.) / transformation->aspect,
        1. - 2. * y / h);
  
    graphene_point3d_init (&ray_clip, graphene_vec2_get_x (&screen_coord),
        graphene_vec2_get_y (&screen_coord), -1.);
    graphene_matrix_transform_point3d (&transformation->inv_projection_matrix,
        &ray_clip, &ray_eye);
  
    graphene_vec3_init (&ray_eye_vec3, ray_eye.x, ray_eye.y, -1.);
  
    if (transformation->ortho) {
      graphene_vec3_init (&ray_ortho_dir, 0., 0., 1.);
  
      ray_origin = &ray_eye_vec3;
      ray_direction = &ray_ortho_dir;
    } else {
      graphene_matrix_transform_vec3 (&transformation->inv_view_matrix,
          &ray_eye_vec3, &ray_world_dir);
      graphene_vec3_normalize (&ray_world_dir, &ray_world_dir);
  
      ray_origin = &transformation->camera_position;
      ray_direction = &ray_world_dir;
    }
  
    graphene_ray_init_from_vec3 (ray, ray_origin, ray_direction);
  
    GST_TRACE_OBJECT (transformation, "Calculated ray origin: " VEC3_FORMAT
        " direction: " VEC3_FORMAT " from screen coordinates: " VEC2_FORMAT
        " with %s projection",
        VEC3_ARGS (ray_origin), VEC3_ARGS (ray_direction),
        VEC2_ARGS (&screen_coord),
        transformation->ortho ? "ortho" : "perspection");
  }
  
  static void
  _init_world_video_plane (GstGLTransformation * transformation,
      graphene_plane_t * video_plane)
  {
    graphene_point3d_t bottom_left, bottom_right, top_left, top_right;
    graphene_point3d_t world_bottom_left, world_bottom_right;
    graphene_point3d_t world_top_left, world_top_right;
  
    graphene_point3d_init (&top_left, -transformation->aspect, 1., 0.);
    graphene_point3d_init (&top_right, transformation->aspect, 1., 0.);
    graphene_point3d_init (&bottom_left, -transformation->aspect, -1., 0.);
    graphene_point3d_init (&bottom_right, transformation->aspect, -1., 0.);
  
    graphene_matrix_transform_point3d (&transformation->model_matrix,
        &bottom_left, &world_bottom_left);
    graphene_matrix_transform_point3d (&transformation->model_matrix,
        &bottom_right, &world_bottom_right);
    graphene_matrix_transform_point3d (&transformation->model_matrix,
        &top_left, &world_top_left);
    graphene_matrix_transform_point3d (&transformation->model_matrix,
        &top_right, &world_top_right);
  
    graphene_plane_init_from_points (video_plane, &world_bottom_left,
        &world_top_right, &world_top_left);
  }
  
  static gboolean
  _screen_coord_to_model_coord (GstGLTransformation * transformation,
      double x, double y, double *res_x, double *res_y)
  {
    GstGLFilter *filter = GST_GL_FILTER (transformation);
    double w = (double) GST_VIDEO_INFO_WIDTH (&filter->in_info);
    double h = (double) GST_VIDEO_INFO_HEIGHT (&filter->in_info);
    graphene_point3d_t world_point, model_coord;
    graphene_plane_t video_plane;
    graphene_ray_t ray;
    double new_x, new_y;
  
    _init_world_video_plane (transformation, &video_plane);
    _screen_coord_to_world_ray (transformation, x, y, &ray);
    _intersect_plane_and_ray (&video_plane, &ray, &world_point);
    graphene_matrix_transform_point3d (&transformation->inv_model_matrix,
        &world_point, &model_coord);
  
    /* ndc to pixels.  We render the frame Y-flipped so need to unflip the
     * y coordinate */
    new_x = (model_coord.x + 1.) * w / 2;
    new_y = (1. - model_coord.y) * h / 2;
  
    if (new_x < 0. || new_x > w || new_y < 0. || new_y > h)
      /* coords off video surface */
      return FALSE;
  
    GST_DEBUG_OBJECT (transformation, "converted %f,%f to %f,%f", x, y, new_x,
        new_y);
  
    if (res_x)
      *res_x = new_x;
    if (res_y)
      *res_y = new_y;
  
    return TRUE;
  }
  
  #if 0
  /* debugging facilities for transforming vertices from model space to screen
   * space */
  static void
  _ndc_to_viewport (GstGLTransformation * transformation, graphene_vec3_t * ndc,
      int x, int y, int w, int h, float near, float far, graphene_vec3_t * result)
  {
    GstGLFilter *filter = GST_GL_FILTER (transformation);
    /* center of the viewport */
    int o_x = x + w / 2;
    int o_y = y + h / 2;
  
    graphene_vec3_init (result, graphene_vec3_get_x (ndc) * w / 2 + o_x,
        graphene_vec3_get_y (ndc) * h / 2 + o_y,
        (far - near) * graphene_vec3_get_z (ndc) / 2 + (far + near) / 2);
  }
  
  static void
  _perspective_division (graphene_vec4_t * clip, graphene_vec3_t * result)
  {
    float w = graphene_vec4_get_w (clip);
  
    graphene_vec3_init (result, graphene_vec4_get_x (clip) / w,
        graphene_vec4_get_y (clip) / w, graphene_vec4_get_z (clip) / w);
  }
  
  static void
  _vertex_to_screen_coord (GstGLTransformation * transformation,
      graphene_vec4_t * vertex, graphene_vec3_t * view)
  {
    GstGLFilter *filter = GST_GL_FILTER (transformation);
    gint w = GST_VIDEO_INFO_WIDTH (&filter->in_info);
    gint h = GST_VIDEO_INFO_HEIGHT (&filter->in_info);
    graphene_vec4_t clip;
    graphene_vec3_t ndc;
  
    graphene_matrix_transform_vec4 (&transformation->mvp_matrix, vertex, &clip);
    _perspective_division (&clip, &ndc);
    _ndc_to_viewport (transformation, &ndc, 0, 0, w, h, 0., 1., view);
  }
  #endif
  
  static gboolean
  gst_gl_transformation_src_event (GstBaseTransform * trans, GstEvent * event)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (trans);
    GstStructure *structure;
    gboolean ret;
  
    GST_DEBUG_OBJECT (trans, "handling %s event", GST_EVENT_TYPE_NAME (event));
  
    switch (GST_EVENT_TYPE (event)) {
      case GST_EVENT_NAVIGATION:{
        gdouble x, y;
        event =
            GST_EVENT (gst_mini_object_make_writable (GST_MINI_OBJECT (event)));
  
        structure = (GstStructure *) gst_event_get_structure (event);
        if (gst_structure_get_double (structure, "pointer_x", &x) &&
            gst_structure_get_double (structure, "pointer_y", &y)) {
          gdouble new_x, new_y;
  
          if (!_screen_coord_to_model_coord (transformation, x, y, &new_x,
                  &new_y)) {
            gst_event_unref (event);
            return TRUE;
          }
  
          gst_structure_set (structure, "pointer_x", G_TYPE_DOUBLE, new_x,
              "pointer_y", G_TYPE_DOUBLE, new_y, NULL);
        }
        break;
      }
      default:
        break;
    }
  
    ret = GST_BASE_TRANSFORM_CLASS (parent_class)->src_event (trans, event);
  
    return ret;
  }
  
  static gboolean
  gst_gl_transformation_filter_meta (GstBaseTransform * trans, GstQuery * query,
      GType api, const GstStructure * params)
  {
    if (api == GST_VIDEO_AFFINE_TRANSFORMATION_META_API_TYPE)
      return TRUE;
  
    if (api == GST_GL_SYNC_META_API_TYPE)
      return TRUE;
  
    return FALSE;
  }
  
  static gboolean
  gst_gl_transformation_decide_allocation (GstBaseTransform * trans,
      GstQuery * query)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (trans);
  
    if (!GST_BASE_TRANSFORM_CLASS (parent_class)->decide_allocation (trans,
            query))
      return FALSE;
  
    if (gst_query_find_allocation_meta (query,
            GST_VIDEO_AFFINE_TRANSFORMATION_META_API_TYPE, NULL)) {
      transformation->downstream_supports_affine_meta = TRUE;
    } else {
      transformation->downstream_supports_affine_meta = FALSE;
    }
  
    return TRUE;
  }
  
  static void
  gst_gl_transformation_gl_stop (GstGLBaseFilter * base_filter)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (base_filter);
    const GstGLFuncs *gl = base_filter->context->gl_vtable;
  
    if (transformation->vao) {
      gl->DeleteVertexArrays (1, &transformation->vao);
      transformation->vao = 0;
    }
  
    if (transformation->vertex_buffer) {
      gl->DeleteBuffers (1, &transformation->vertex_buffer);
      transformation->vertex_buffer = 0;
    }
  
    if (transformation->vbo_indices) {
      gl->DeleteBuffers (1, &transformation->vbo_indices);
      transformation->vbo_indices = 0;
    }
  
    if (transformation->shader) {
      gst_object_unref (transformation->shader);
      transformation->shader = NULL;
    }
  
    GST_GL_BASE_FILTER_CLASS (parent_class)->gl_stop (base_filter);
  }
  
  static gboolean
  gst_gl_transformation_gl_start (GstGLBaseFilter * base_filter)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (base_filter);
  
    if (!GST_GL_BASE_FILTER_CLASS (parent_class)->gl_start (base_filter))
      return FALSE;
  
    if (gst_gl_context_get_gl_api (base_filter->context)) {
      gchar *frag_str;
      gboolean ret;
  
      frag_str =
          gst_gl_shader_string_fragment_get_default (base_filter->context,
          GST_GLSL_VERSION_NONE,
          GST_GLSL_PROFILE_ES | GST_GLSL_PROFILE_COMPATIBILITY);
  
      /* blocking call, wait until the opengl thread has compiled the shader */
      ret = gst_gl_context_gen_shader (base_filter->context,
          gst_gl_shader_string_vertex_mat4_vertex_transform,
          frag_str, &transformation->shader);
  
      g_free (frag_str);
  
      return ret;
    }
    return TRUE;
  }
  
  static GstFlowReturn
  gst_gl_transformation_prepare_output_buffer (GstBaseTransform * trans,
      GstBuffer * inbuf, GstBuffer ** outbuf)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (trans);
    GstGLFilter *filter = GST_GL_FILTER (trans);
  
    if (transformation->downstream_supports_affine_meta &&
        gst_video_info_is_equal (&filter->in_info, &filter->out_info)) {
      GstVideoAffineTransformationMeta *af_meta;
      graphene_matrix_t upstream_matrix, tmp, tmp2, inv_aspect, yflip;
      float upstream[16], downstream[16];
  
      *outbuf = gst_buffer_make_writable (inbuf);
  
      af_meta = gst_buffer_get_video_affine_transformation_meta (inbuf);
      if (!af_meta)
        af_meta = gst_buffer_add_video_affine_transformation_meta (*outbuf);
  
      GST_LOG_OBJECT (trans, "applying transformation to existing affine "
          "transformation meta");
  
      gst_gl_get_affine_transformation_meta_as_ndc_ext (af_meta, upstream);
  
      /* apply the transformation to the existing affine meta */
      graphene_matrix_init_from_float (&upstream_matrix, upstream);
      graphene_matrix_init_scale (&inv_aspect, transformation->aspect, -1., 1.);
      graphene_matrix_init_scale (&yflip, 1., -1., 1.);
  
      /* invert the aspect effects */
      graphene_matrix_multiply (&upstream_matrix, &inv_aspect, &tmp2);
      /* apply the transformation */
      graphene_matrix_multiply (&tmp2, &transformation->mvp_matrix, &tmp);
      /* and undo yflip */
      graphene_matrix_multiply (&tmp, &yflip, &tmp2);
  
      graphene_matrix_to_float (&tmp2, downstream);
      gst_gl_set_affine_transformation_meta_from_ndc_ext (af_meta, downstream);
  
      return GST_FLOW_OK;
    }
  
    return GST_BASE_TRANSFORM_CLASS (parent_class)->prepare_output_buffer (trans,
        inbuf, outbuf);
  }
  
  static gboolean
  gst_gl_transformation_filter (GstGLFilter * filter,
      GstBuffer * inbuf, GstBuffer * outbuf)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (filter);
  
    if (transformation->downstream_supports_affine_meta &&
        gst_video_info_is_equal (&filter->in_info, &filter->out_info)) {
      return TRUE;
    } else {
      return gst_gl_filter_filter_texture (filter, inbuf, outbuf);
    }
  }
  
  static gboolean
  gst_gl_transformation_filter_texture (GstGLFilter * filter,
      GstGLMemory * in_tex, GstGLMemory * out_tex)
  {
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (filter);
  
    transformation->in_tex = in_tex;
  
    gst_gl_framebuffer_draw_to_texture (filter->fbo, out_tex,
        (GstGLFramebufferFunc) gst_gl_transformation_callback, transformation);
  
    return TRUE;
  }
  
  static const GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
  
  static void
  _upload_vertices (GstGLTransformation * transformation)
  {
    const GstGLFuncs *gl =
        GST_GL_BASE_FILTER (transformation)->context->gl_vtable;
  
  /* *INDENT-OFF* */
    GLfloat vertices[] = {
       -transformation->aspect, -1.0,  0.0, 1.0, 0.0, 0.0,
        transformation->aspect, -1.0,  0.0, 1.0, 1.0, 0.0,
        transformation->aspect,  1.0,  0.0, 1.0, 1.0, 1.0,
       -transformation->aspect,  1.0,  0.0, 1.0, 0.0, 1.0,
    };
    /* *INDENT-ON* */
  
    gl->BindBuffer (GL_ARRAY_BUFFER, transformation->vertex_buffer);
  
    gl->BufferData (GL_ARRAY_BUFFER, 4 * 6 * sizeof (GLfloat), vertices,
        GL_STATIC_DRAW);
  }
  
  static void
  _bind_buffer (GstGLTransformation * transformation)
  {
    const GstGLFuncs *gl =
        GST_GL_BASE_FILTER (transformation)->context->gl_vtable;
  
    gl->BindBuffer (GL_ELEMENT_ARRAY_BUFFER, transformation->vbo_indices);
    gl->BindBuffer (GL_ARRAY_BUFFER, transformation->vertex_buffer);
  
    /* Load the vertex position */
    gl->VertexAttribPointer (transformation->attr_position, 4, GL_FLOAT,
        GL_FALSE, 6 * sizeof (GLfloat), (void *) 0);
  
    /* Load the texture coordinate */
    gl->VertexAttribPointer (transformation->attr_texture, 2, GL_FLOAT, GL_FALSE,
        6 * sizeof (GLfloat), (void *) (4 * sizeof (GLfloat)));
  
    gl->EnableVertexAttribArray (transformation->attr_position);
    gl->EnableVertexAttribArray (transformation->attr_texture);
  }
  
  static void
  _unbind_buffer (GstGLTransformation * transformation)
  {
    const GstGLFuncs *gl =
        GST_GL_BASE_FILTER (transformation)->context->gl_vtable;
  
    gl->BindBuffer (GL_ELEMENT_ARRAY_BUFFER, 0);
    gl->BindBuffer (GL_ARRAY_BUFFER, 0);
  
    gl->DisableVertexAttribArray (transformation->attr_position);
    gl->DisableVertexAttribArray (transformation->attr_texture);
  }
  
  static gboolean
  gst_gl_transformation_callback (gpointer stuff)
  {
    GstGLFilter *filter = GST_GL_FILTER (stuff);
    GstGLTransformation *transformation = GST_GL_TRANSFORMATION (filter);
    GstGLFuncs *gl = GST_GL_BASE_FILTER (filter)->context->gl_vtable;
  
    GLfloat temp_matrix[16];
  
    gst_gl_context_clear_shader (GST_GL_BASE_FILTER (filter)->context);
    gl->BindTexture (GL_TEXTURE_2D, 0);
  
    gl->ClearColor (0.f, 0.f, 0.f, 0.f);
    gl->Clear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  
    gst_gl_shader_use (transformation->shader);
  
    gl->ActiveTexture (GL_TEXTURE0);
    gl->BindTexture (GL_TEXTURE_2D, transformation->in_tex->tex_id);
    gst_gl_shader_set_uniform_1i (transformation->shader, "texture", 0);
  
    graphene_matrix_to_float (&transformation->mvp_matrix, temp_matrix);
    gst_gl_shader_set_uniform_matrix_4fv (transformation->shader,
        "u_transformation", 1, GL_FALSE, temp_matrix);
  
    if (!transformation->vertex_buffer) {
      transformation->attr_position =
          gst_gl_shader_get_attribute_location (transformation->shader,
          "a_position");
  
      transformation->attr_texture =
          gst_gl_shader_get_attribute_location (transformation->shader,
          "a_texcoord");
  
      if (gl->GenVertexArrays) {
        gl->GenVertexArrays (1, &transformation->vao);
        gl->BindVertexArray (transformation->vao);
      }
  
      gl->GenBuffers (1, &transformation->vertex_buffer);
  
      gl->GenBuffers (1, &transformation->vbo_indices);
      gl->BindBuffer (GL_ELEMENT_ARRAY_BUFFER, transformation->vbo_indices);
      gl->BufferData (GL_ELEMENT_ARRAY_BUFFER, sizeof (indices), indices,
          GL_STATIC_DRAW);
  
      transformation->caps_change = TRUE;
    }
  
    if (gl->GenVertexArrays)
      gl->BindVertexArray (transformation->vao);
  
    if (transformation->caps_change)
      _upload_vertices (transformation);
    _bind_buffer (transformation);
  
    gl->DrawElements (GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0);
  
    if (gl->GenVertexArrays)
      gl->BindVertexArray (0);
    else
      _unbind_buffer (transformation);
  
    gst_gl_context_clear_shader (GST_GL_BASE_FILTER (filter)->context);
    transformation->caps_change = FALSE;
  
    return TRUE;
  }
  