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# Draws an off-screen buffer and display it in the corner of the view.
import bpy
import bgl
import gpu
import numpy as np
g_imageVertSrc = '''
in vec2 texCoord;
in vec2 pos;
out vec2 texCoord_interp;
void main()
{
gl_Position = vec4(pos.xy, 0.0f, 1.0);
gl_Position.z = 1.0f;
texCoord_interp = texCoord;
}
'''
g_imageFragSrc = '''
in vec2 texCoord_interp;
out vec4 fragColor;
uniform sampler2D image;
void main()
{
fragColor = texture(image, texCoord_interp);
}
'''
g_plane_vertices = np.array([
([-1.0, -1.0], [0.0, 0.0]),
([1.0, -1.0], [1.0, 0.0]),
([1.0, 1.0], [1.0, 1.0]),
([1.0, 1.0], [1.0, 1.0]),
([-1.0, 1.0], [0.0, 1.0]),
([-1.0, -1.0], [0.0, 0.0]),
], [('pos', 'f4', 2), ('uv', 'f4', 2)])
class VIEW3D_OT_draw_offscreen(bpy.types.Operator):
bl_idname = "view3d.offscreen_draw"
bl_label = "Viewport Offscreen Draw"
_handle_calc = None
_handle_draw = None
is_enabled = False
global_shader = None
batch_plane = None
uniform_image = -1
shader = None
# manage draw handler
@staticmethod
def draw_callback_px(self, context):
scene = context.scene
aspect_ratio = scene.render.resolution_x / scene.render.resolution_y
self._update_offscreen(context, self._offscreen)
self._opengl_draw(context, self._texture, aspect_ratio, 0.2)
@staticmethod
def handle_add(self, context):
VIEW3D_OT_draw_offscreen._handle_draw = bpy.types.SpaceView3D.draw_handler_add(
self.draw_callback_px, (self, context),
'WINDOW', 'POST_PIXEL',
)
@staticmethod
def handle_remove():
if VIEW3D_OT_draw_offscreen._handle_draw is not None:
bpy.types.SpaceView3D.draw_handler_remove(VIEW3D_OT_draw_offscreen._handle_draw, 'WINDOW')
VIEW3D_OT_draw_offscreen._handle_draw = None
# off-screen buffer
@staticmethod
def _setup_offscreen(context):
scene = context.scene
aspect_ratio = scene.render.resolution_x / scene.render.resolution_y
try:
offscreen = gpu.types.GPUOffScreen(512, int(512 / aspect_ratio))
except Exception as e:
print(e)
offscreen = None
return offscreen
@staticmethod
def _update_offscreen(context, offscreen):
scene = context.scene
view_layer = context.view_layer
render = scene.render
camera = scene.camera
modelview_matrix = camera.matrix_world.inverted()
projection_matrix = camera.calc_matrix_camera(
context.depsgraph,
x=render.resolution_x,
y=render.resolution_y,
scale_x=render.pixel_aspect_x,
scale_y=render.pixel_aspect_y,
)
offscreen.draw_view3d(
scene,
view_layer,
context.space_data,
context.region,
projection_matrix,
modelview_matrix,
)
def _opengl_draw(self, context, texture, aspect_ratio, scale):
"""
OpenGL code to draw a rectangle in the viewport
"""
# view setup
bgl.glDisable(bgl.GL_DEPTH_TEST)
viewport = bgl.Buffer(bgl.GL_INT, 4)
bgl.glGetIntegerv(bgl.GL_VIEWPORT, viewport)
active_texture = bgl.Buffer(bgl.GL_INT, 1)
bgl.glGetIntegerv(bgl.GL_TEXTURE_2D, active_texture)
width = int(scale * viewport[2])
height = int(width / aspect_ratio)
bgl.glViewport(viewport[0], viewport[1], width, height)
bgl.glScissor(viewport[0], viewport[1], width, height)
# draw routine
batch_plane = self.get_batch_plane()
shader = VIEW3D_OT_draw_offscreen.shader
# bind it so we can pass the new uniform values
shader.bind()
bgl.glEnable(bgl.GL_TEXTURE_2D)
bgl.glActiveTexture(bgl.GL_TEXTURE0)
bgl.glBindTexture(bgl.GL_TEXTURE_2D, texture)
shader.uniform_int(VIEW3D_OT_draw_offscreen.uniform_image, 0)
batch_plane.draw()
# restoring settings
bgl.glBindTexture(bgl.GL_TEXTURE_2D, active_texture[0])
bgl.glDisable(bgl.GL_TEXTURE_2D)
# reset view
bgl.glViewport(viewport[0], viewport[1], viewport[2], viewport[3])
bgl.glScissor(viewport[0], viewport[1], viewport[2], viewport[3])
def get_batch_plane(self):
if self.batch_plane is None:
global g_plane_vertices
format = gpu.types.GPUVertFormat()
pos_id = format.attr_add(
id="pos",
comp_type="F32",
len=2,
fetch_mode="FLOAT")
uv_id = format.attr_add(
id="texCoord",
comp_type="F32",
len=2,
fetch_mode="FLOAT")
vbo = gpu.types.GPUVertBuf(
len=len(g_plane_vertices),
format=format)
vbo.fill(id=pos_id, data=g_plane_vertices["pos"])
vbo.fill(id=uv_id, data=g_plane_vertices["uv"])
batch_plane = gpu.types.GPUBatch(type="TRIS", buf=vbo)
shader = self.global_shader
VIEW3D_OT_draw_offscreen.shader = shader
VIEW3D_OT_draw_offscreen.uniform_image = shader.uniform_from_name("image")
batch_plane.program_set(shader)
VIEW3D_OT_draw_offscreen.batch_plane = batch_plane
return VIEW3D_OT_draw_offscreen.batch_plane
# operator functions
@classmethod
def poll(cls, context):
return context.area.type == 'VIEW_3D'
def modal(self, context, event):
if context.area:
context.area.tag_redraw()
if event.type in {'RIGHTMOUSE', 'ESC'}:
self.cancel(context)
return {'CANCELLED'}
return {'PASS_THROUGH'}
def invoke(self, context, event):
if VIEW3D_OT_draw_offscreen.is_enabled:
self.cancel(context)
return {'FINISHED'}
else:
self._offscreen = VIEW3D_OT_draw_offscreen._setup_offscreen(context)
if self._offscreen:
self._texture = self._offscreen.color_texture
else:
self.report({'ERROR'}, "Error initializing offscreen buffer. More details in the console")
return {'CANCELLED'}
VIEW3D_OT_draw_offscreen.handle_add(self, context)
VIEW3D_OT_draw_offscreen.is_enabled = True
if context.area:
context.area.tag_redraw()
context.window_manager.modal_handler_add(self)
return {'RUNNING_MODAL'}
def cancel(self, context):
VIEW3D_OT_draw_offscreen.handle_remove()
VIEW3D_OT_draw_offscreen.is_enabled = False
if VIEW3D_OT_draw_offscreen.batch_plane is not None:
del VIEW3D_OT_draw_offscreen.batch_plane
VIEW3D_OT_draw_offscreen.batch_plane = None
VIEW3D_OT_draw_offscreen.shader = None
if context.area:
context.area.tag_redraw()
def register():
shader = gpu.types.GPUShader(g_imageVertSrc, g_imageFragSrc)
VIEW3D_OT_draw_offscreen.global_shader = shader
bpy.utils.register_class(VIEW3D_OT_draw_offscreen)
def unregister():
bpy.utils.unregister_class(VIEW3D_OT_draw_offscreen)
VIEW3D_OT_draw_offscreen.global_shader = None
if __name__ == "__main__":
try:
unregister()
except RuntimeError:
pass
else:
if hasattr(bpy.types, "VIEW3D_OT_draw_offscreen"):
del bpy.types.VIEW3D_OT_draw_offscreen.global_shader
register()
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