Welcome to mirror list, hosted at ThFree Co, Russian Federation.

gpu_framebuffer.c « intern « gpu « blender « source - git.blender.org/blender.git - Unnamed repository; edit this file 'description' to name the repository.
summaryrefslogtreecommitdiff
blob: eabd501f1d5d0a7590a2532c564c426149aa7cb2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2005 Blender Foundation.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): Brecht Van Lommel.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include "MEM_guardedalloc.h"

#include "BLI_blenlib.h"
#include "BLI_threads.h"
#include "BLI_utildefines.h"
#include "BLI_math_base.h"

#include "BKE_global.h"

#include "GPU_batch.h"
#include "GPU_draw.h"
#include "GPU_extensions.h"
#include "GPU_framebuffer.h"
#include "GPU_matrix.h"
#include "GPU_shader.h"
#include "GPU_texture.h"

#include "intern/gpu_private.h"

static ThreadLocal(void *) g_currentfb;

typedef enum {
	GPU_FB_DEPTH_ATTACHMENT = 0,
	GPU_FB_DEPTH_STENCIL_ATTACHMENT,
	GPU_FB_COLOR_ATTACHMENT0,
	GPU_FB_COLOR_ATTACHMENT1,
	GPU_FB_COLOR_ATTACHMENT2,
	GPU_FB_COLOR_ATTACHMENT3,
	GPU_FB_COLOR_ATTACHMENT4,
	/* Number of maximum output slots.
	 * We support 5 outputs for now (usually we wouldn't need more to preserve fill rate). */
	/* Keep in mind that GL max is GL_MAX_DRAW_BUFFERS and is at least 8, corresponding to
	 * the maximum number of COLOR attachments specified by glDrawBuffers. */
	GPU_FB_MAX_ATTACHEMENT
} GPUAttachmentType;

#define GPU_FB_MAX_COLOR_ATTACHMENT (GPU_FB_MAX_ATTACHEMENT - GPU_FB_COLOR_ATTACHMENT0)

#define GPU_FB_DIRTY_DRAWBUFFER (1 << 15)

#define GPU_FB_ATTACHEMENT_IS_DIRTY(flag, type) ((flag & (1 << type)) != 0)
#define GPU_FB_ATTACHEMENT_SET_DIRTY(flag, type) (flag |= (1 << type))

struct GPUFrameBuffer {
	GLuint object;
	GPUAttachment attachments[GPU_FB_MAX_ATTACHEMENT];
	uint16_t dirty_flag;
	int width, height;
	bool multisample;
	/* TODO Check that we always use the right context when binding
	 * (FBOs are not shared accross ogl contexts). */
	// void *ctx;
};

static GLenum convert_attachment_type_to_gl(GPUAttachmentType type)
{
	static const GLenum table[] = {
		[GPU_FB_DEPTH_ATTACHMENT] = GL_DEPTH_ATTACHMENT,
		[GPU_FB_DEPTH_STENCIL_ATTACHMENT] = GL_DEPTH_STENCIL_ATTACHMENT,
		[GPU_FB_COLOR_ATTACHMENT0] = GL_COLOR_ATTACHMENT0,
		[GPU_FB_COLOR_ATTACHMENT1] = GL_COLOR_ATTACHMENT1,
		[GPU_FB_COLOR_ATTACHMENT2] = GL_COLOR_ATTACHMENT2,
		[GPU_FB_COLOR_ATTACHMENT3] = GL_COLOR_ATTACHMENT3,
		[GPU_FB_COLOR_ATTACHMENT4] = GL_COLOR_ATTACHMENT4
	};
	return table[type];
}

static GPUAttachmentType attachment_type_from_tex(GPUTexture *tex, int slot)
{
	switch (GPU_texture_format(tex)) {
		case GPU_DEPTH_COMPONENT32F:
		case GPU_DEPTH_COMPONENT24:
		case GPU_DEPTH_COMPONENT16:
			return GPU_FB_DEPTH_ATTACHMENT;
		case GPU_DEPTH24_STENCIL8:
			return GPU_FB_DEPTH_STENCIL_ATTACHMENT;
		default:
			return GPU_FB_COLOR_ATTACHMENT0 + slot;
	}
}

static GLenum convert_buffer_bits_to_gl(GPUFrameBufferBits bits)
{
	GLbitfield mask = 0;
	mask |= (bits & GPU_DEPTH_BIT) ? GL_DEPTH_BUFFER_BIT : 0;
	mask |= (bits & GPU_STENCIL_BIT) ? GL_STENCIL_BUFFER_BIT : 0;
	mask |= (bits & GPU_COLOR_BIT) ? GL_COLOR_BUFFER_BIT : 0;
	return mask;
}

static GPUTexture *framebuffer_get_depth_tex(GPUFrameBuffer *fb)
{
	if (fb->attachments[GPU_FB_DEPTH_ATTACHMENT].tex)
		return fb->attachments[GPU_FB_DEPTH_ATTACHMENT].tex;
	else
		return fb->attachments[GPU_FB_DEPTH_STENCIL_ATTACHMENT].tex;;
}

static GPUTexture *framebuffer_get_color_tex(GPUFrameBuffer *fb, int slot)
{
	return fb->attachments[GPU_FB_COLOR_ATTACHMENT0 + slot].tex;
}

static void gpu_print_framebuffer_error(GLenum status, char err_out[256])
{
	const char *format = "GPUFrameBuffer: framebuffer status %s\n";
	const char *err = "unknown";

#define format_status(X) \
	case GL_FRAMEBUFFER_##X: err = "GL_FRAMEBUFFER_"#X; \
		break;

	switch (status) {
		/* success */
		format_status(COMPLETE)
		/* errors shared by OpenGL desktop & ES */
		format_status(INCOMPLETE_ATTACHMENT)
		format_status(INCOMPLETE_MISSING_ATTACHMENT)
		format_status(UNSUPPORTED)
#if 0 /* for OpenGL ES only */
		format_status(INCOMPLETE_DIMENSIONS)
#else /* for desktop GL only */
		format_status(INCOMPLETE_DRAW_BUFFER)
		format_status(INCOMPLETE_READ_BUFFER)
		format_status(INCOMPLETE_MULTISAMPLE)
		format_status(UNDEFINED)
#endif
	}

#undef format_status

	if (err_out) {
		BLI_snprintf(err_out, 256, format, err);
	}
	else {
		fprintf(stderr, format, err);
	}
}

void gpu_framebuffer_module_init(void)
{
    BLI_thread_local_create(g_currentfb);
}

void gpu_framebuffer_module_exit(void)
{
    BLI_thread_local_delete(g_currentfb);
}

static uint gpu_framebuffer_current_get(void)
{
	return GET_UINT_FROM_POINTER(BLI_thread_local_get(g_currentfb));
}

static void gpu_framebuffer_current_set(uint object)
{
	BLI_thread_local_set(g_currentfb, SET_UINT_IN_POINTER(object));
}

/* GPUFrameBuffer */

GPUFrameBuffer *GPU_framebuffer_create(void)
{
	/* We generate the FB object later at first use in order to
	 * create the framebuffer in the right opengl context. */
	return MEM_callocN(sizeof(GPUFrameBuffer), "GPUFrameBuffer");;
}

static void gpu_framebuffer_init(GPUFrameBuffer *fb)
{
	glGenFramebuffers(1, &fb->object);
}

void GPU_framebuffer_free(GPUFrameBuffer *fb)
{
	for (GPUAttachmentType type = 0; type < GPU_FB_MAX_ATTACHEMENT; type++) {
		if (fb->attachments[type].tex != NULL) {
			GPU_framebuffer_texture_detach(fb, fb->attachments[type].tex);
		}
	}

	/* This restores the framebuffer if it was bound */
	glDeleteFramebuffers(1, &fb->object);

	if (gpu_framebuffer_current_get() == fb->object) {
		gpu_framebuffer_current_set(0);
	}

	MEM_freeN(fb);
}

/* ---------- Attach ----------- */

static void gpu_framebuffer_texture_attach_ex(GPUFrameBuffer *fb, GPUTexture *tex, int slot, int layer, int mip)
{
	if (slot >= GPU_FB_MAX_COLOR_ATTACHMENT) {
		fprintf(stderr,
		        "Attaching to index %d framebuffer slot unsupported. "
		        "Use at most %d\n", slot, GPU_FB_MAX_COLOR_ATTACHMENT);
		return;
	}

	GPUAttachmentType type = attachment_type_from_tex(tex, slot);
	GPUAttachment *attachment = &fb->attachments[type];

	if ((attachment->tex == tex) &&
	    (attachment->mip == mip) &&
	    (attachment->layer == layer))
	{
		return; /* Exact same texture already bound here. */
	}
	else if (attachment->tex != NULL) {
		GPU_framebuffer_texture_detach(fb, attachment->tex);
	}

	if (attachment->tex == NULL) {
		GPU_texture_attach_framebuffer(tex, fb, type);
	}

	attachment->tex = tex;
	attachment->mip = mip;
	attachment->layer = layer;
	GPU_FB_ATTACHEMENT_SET_DIRTY(fb->dirty_flag, type);
}

void GPU_framebuffer_texture_attach(GPUFrameBuffer *fb, GPUTexture *tex, int slot, int mip)
{
	gpu_framebuffer_texture_attach_ex(fb, tex, slot, -1, mip);
}

void GPU_framebuffer_texture_layer_attach(GPUFrameBuffer *fb, GPUTexture *tex, int slot, int layer, int mip)
{
	/* NOTE: We could support 1D ARRAY texture. */
	BLI_assert(GPU_texture_target(tex) == GL_TEXTURE_2D_ARRAY);
	gpu_framebuffer_texture_attach_ex(fb, tex, slot, layer, mip);
}

void GPU_framebuffer_texture_cubeface_attach(GPUFrameBuffer *fb, GPUTexture *tex, int slot, int face, int mip)
{
	BLI_assert(GPU_texture_cube(tex));
	gpu_framebuffer_texture_attach_ex(fb, tex, slot, face, mip);
}

/* ---------- Detach ----------- */

void GPU_framebuffer_texture_detach_slot(GPUFrameBuffer *fb, GPUTexture *tex, int type)
{
	GPUAttachment *attachment = &fb->attachments[type];

	if (attachment->tex != tex) {
		fprintf(stderr,
		        "Warning, attempting to detach Texture %p from framebuffer %p "
		        "but texture is not attached.\n", tex, fb);
		return;
	}

	attachment->tex = NULL;
	GPU_FB_ATTACHEMENT_SET_DIRTY(fb->dirty_flag, type);
}

void GPU_framebuffer_texture_detach(GPUFrameBuffer *fb, GPUTexture *tex)
{
	GPUAttachmentType type = GPU_texture_detach_framebuffer(tex, fb);
	GPU_framebuffer_texture_detach_slot(fb, tex, type);
}

/* ---------- Config (Attach & Detach) ----------- */

/**
 * First GPUAttachment in *config is always the depth/depth_stencil buffer.
 * Following GPUAttachments are color buffers.
 * Setting GPUAttachment.mip to -1 will leave the texture in this slot.
 * Setting GPUAttachment.tex to NULL will detach the texture in this slot.
 **/
void GPU_framebuffer_config_array(GPUFrameBuffer *fb, const GPUAttachment *config, int config_ct)
{
	if (config[0].tex) {
		BLI_assert(GPU_texture_depth(config[0].tex));
		gpu_framebuffer_texture_attach_ex(fb, config[0].tex, 0, config[0].layer, config[0].mip);
	}
	else if (config[0].mip == -1) {
		/* Leave texture attached */
	}
	else if (fb->attachments[GPU_FB_DEPTH_ATTACHMENT].tex != NULL) {
		GPU_framebuffer_texture_detach(fb, fb->attachments[GPU_FB_DEPTH_ATTACHMENT].tex);
	}
	else if (fb->attachments[GPU_FB_DEPTH_STENCIL_ATTACHMENT].tex != NULL) {
		GPU_framebuffer_texture_detach(fb, fb->attachments[GPU_FB_DEPTH_STENCIL_ATTACHMENT].tex);
	}

	int slot = 0;
	for (int i = 1; i < config_ct; ++i, ++slot) {
		if (config[i].tex != NULL) {
			BLI_assert(GPU_texture_depth(config[i].tex) == false);
			gpu_framebuffer_texture_attach_ex(fb, config[i].tex, slot, config[i].layer, config[i].mip);
		}
		else if (config[i].mip != -1) {
			GPUTexture *tex = framebuffer_get_color_tex(fb, slot);
			if (tex != NULL) {
				GPU_framebuffer_texture_detach(fb, tex);
			}
		}
	}
}

/* ---------- Bind / Restore ----------- */

static void gpu_framebuffer_attachment_attach(GPUAttachment *attach, GPUAttachmentType attach_type)
{
	int tex_bind = GPU_texture_opengl_bindcode(attach->tex);
	GLenum gl_attachment = convert_attachment_type_to_gl(attach_type);

	if (attach->layer > -1) {
		if (GPU_texture_cube(attach->tex)) {
			glFramebufferTexture2D(GL_FRAMEBUFFER, gl_attachment, GL_TEXTURE_CUBE_MAP_POSITIVE_X + attach->layer,
			                       tex_bind, attach->mip);
		}
		else {
			glFramebufferTextureLayer(GL_FRAMEBUFFER, gl_attachment, tex_bind, attach->mip, attach->layer);
		}
	}
	else {
		glFramebufferTexture(GL_FRAMEBUFFER, gl_attachment, tex_bind, attach->mip);
	}
}

static void gpu_framebuffer_attachment_detach(GPUAttachment *UNUSED(attachment), GPUAttachmentType attach_type)
{
	GLenum gl_attachment = convert_attachment_type_to_gl(attach_type);
	glFramebufferTexture(GL_FRAMEBUFFER, gl_attachment, 0, 0);
}

static void gpu_framebuffer_update_attachments(GPUFrameBuffer *fb)
{
	GLenum gl_attachments[GPU_FB_MAX_COLOR_ATTACHMENT];
	int numslots = 0;

	BLI_assert(gpu_framebuffer_current_get() == fb->object);

	/* Update attachments */
	for (GPUAttachmentType type = 0; type < GPU_FB_MAX_ATTACHEMENT; ++type) {

		if (type >= GPU_FB_COLOR_ATTACHMENT0) {
			if (fb->attachments[type].tex) {
				gl_attachments[numslots] = convert_attachment_type_to_gl(type);
			}
			else {
				gl_attachments[numslots] = GL_NONE;
			}
			numslots++;
		}

		if (GPU_FB_ATTACHEMENT_IS_DIRTY(fb->dirty_flag, type) == false) {
			continue;
		}
		else if (fb->attachments[type].tex != NULL) {
			gpu_framebuffer_attachment_attach(&fb->attachments[type], type);

			fb->multisample = (GPU_texture_samples(fb->attachments[type].tex) > 0);
			fb->width = GPU_texture_width(fb->attachments[type].tex);
			fb->height = GPU_texture_height(fb->attachments[type].tex);
		}
		else {
			gpu_framebuffer_attachment_detach(&fb->attachments[type], type);
		}
	}
	fb->dirty_flag = 0;

	/* Update draw buffers (color targets)
	 * This state is saved in the FBO */
	if (numslots)
		glDrawBuffers(numslots, gl_attachments);
	else
		glDrawBuffer(GL_NONE);
}

void GPU_framebuffer_bind(GPUFrameBuffer *fb)
{
	if (fb->object == 0)
		gpu_framebuffer_init(fb);

	if (gpu_framebuffer_current_get() != fb->object)
		glBindFramebuffer(GL_FRAMEBUFFER, fb->object);

	gpu_framebuffer_current_set(fb->object);

	if (fb->dirty_flag != 0)
		gpu_framebuffer_update_attachments(fb);

	/* TODO manually check for errors? */
#if 0
	char err_out[256];
	if (!GPU_framebuffer_check_valid(fb, err_out)) {
		printf("Invalid %s\n", err_out);
	}
#endif

	if (fb->multisample)
		glEnable(GL_MULTISAMPLE);

	glViewport(0, 0, fb->width, fb->height);
}

void GPU_framebuffer_restore(void)
{
	if (gpu_framebuffer_current_get() != 0) {
		glBindFramebuffer(GL_FRAMEBUFFER, 0);
		gpu_framebuffer_current_set(0);
	}
}

bool GPU_framebuffer_bound(GPUFrameBuffer *fb)
{
	return (fb->object == gpu_framebuffer_current_get()) && (fb->object != 0);
}

unsigned int GPU_framebuffer_current_get(void)
{
	return gpu_framebuffer_current_get();
}

bool GPU_framebuffer_check_valid(GPUFrameBuffer *fb, char err_out[256])
{
	if (!GPU_framebuffer_bound(fb))
		GPU_framebuffer_bind(fb);

	GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);

	if (status != GL_FRAMEBUFFER_COMPLETE) {
		GPU_framebuffer_restore();
		gpu_print_framebuffer_error(status, err_out);
		return false;
	}

	return true;
}

/* ---------- Framebuffer Operations ----------- */

#define CHECK_FRAMEBUFFER_IS_BOUND(_fb) \
	BLI_assert(GPU_framebuffer_bound(_fb)); \
	UNUSED_VARS_NDEBUG(_fb);

/* Needs to be done after binding. */
void GPU_framebuffer_viewport_set(GPUFrameBuffer *fb, int x, int y, int w, int h)
{
	CHECK_FRAMEBUFFER_IS_BOUND(fb);

	glViewport(x, y, w, h);
}

void GPU_framebuffer_clear(
        GPUFrameBuffer *fb, GPUFrameBufferBits buffers,
        const float clear_col[4], float clear_depth, unsigned int clear_stencil)
{
	CHECK_FRAMEBUFFER_IS_BOUND(fb);

	if (buffers & GPU_COLOR_BIT) {
		glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
		glClearColor(clear_col[0], clear_col[1], clear_col[2], clear_col[3]);
	}
	if (buffers & GPU_DEPTH_BIT) {
		glDepthMask(GL_TRUE);
		glClearDepth(clear_depth);
	}
	if (buffers & GPU_STENCIL_BIT) {
		glStencilMask(clear_stencil);
	}

	GLbitfield mask = convert_buffer_bits_to_gl(buffers);
	glClear(mask);
}

void GPU_framebuffer_read_depth(GPUFrameBuffer *fb, int x, int y, int w, int h, float *data)
{
	CHECK_FRAMEBUFFER_IS_BOUND(fb);

	GLenum type = GL_DEPTH_COMPONENT;
	glReadBuffer(GL_COLOR_ATTACHMENT0); /* This is OK! */
	glReadPixels(x, y, w, h, type, GL_FLOAT, data);
}

void GPU_framebuffer_read_color(
        GPUFrameBuffer *fb, int x, int y, int w, int h, int channels, int slot, float *data)
{
	CHECK_FRAMEBUFFER_IS_BOUND(fb);

	GLenum type;
	switch (channels) {
		case 1: type = GL_RED; break;
		case 2: type = GL_RG; break;
		case 3: type = GL_RGB; break;
		case 4: type = GL_RGBA;	break;
		default:
			BLI_assert(false && "wrong number of read channels");
			return;
	}
	glReadBuffer(GL_COLOR_ATTACHMENT0 + slot);
	glReadPixels(x, y, w, h, type, GL_FLOAT, data);
}

/* read_slot and write_slot are only used for color buffers. */
void GPU_framebuffer_blit(
        GPUFrameBuffer *fb_read, int read_slot,
        GPUFrameBuffer *fb_write, int write_slot,
        GPUFrameBufferBits blit_buffers)
{
	BLI_assert(blit_buffers != 0);

	GLuint prev_fb = gpu_framebuffer_current_get();

	/* Framebuffers must be up to date. This simplify this function. */
	if (fb_read->dirty_flag != 0 || fb_read->object == 0) {
		GPU_framebuffer_bind(fb_read);
	}
	if (fb_write->dirty_flag != 0 || fb_write->object == 0) {
		GPU_framebuffer_bind(fb_write);
	}

	const bool do_color = (blit_buffers & GPU_COLOR_BIT);
	const bool do_depth = (blit_buffers & GPU_DEPTH_BIT);
	const bool do_stencil = (blit_buffers & GPU_STENCIL_BIT);

	GPUTexture *read_tex = (do_depth || do_stencil)
	                       ? framebuffer_get_depth_tex(fb_read)
	                       : framebuffer_get_color_tex(fb_read, read_slot);
	GPUTexture *write_tex = (do_depth || do_stencil)
	                        ? framebuffer_get_depth_tex(fb_write)
	                        : framebuffer_get_color_tex(fb_write, read_slot);

	if (do_depth) {
		BLI_assert(GPU_texture_depth(read_tex) && GPU_texture_depth(write_tex));
		BLI_assert(GPU_texture_format(read_tex) == GPU_texture_format(write_tex));
	}
	if (do_stencil) {
		BLI_assert(GPU_texture_stencil(read_tex) && GPU_texture_stencil(write_tex));
		BLI_assert(GPU_texture_format(read_tex) == GPU_texture_format(write_tex));
	}
	if (GPU_texture_samples(write_tex) != 0 ||
	    GPU_texture_samples(read_tex) != 0)
	{
		/* Can only blit multisample textures to another texture of the same size. */
		BLI_assert((fb_read->width == fb_write->width) &&
		           (fb_read->height == fb_write->height));
	}

	glBindFramebuffer(GL_READ_FRAMEBUFFER, fb_read->object);
	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fb_write->object);

	if (do_color) {
		glReadBuffer(GL_COLOR_ATTACHMENT0 + read_slot);
		glDrawBuffer(GL_COLOR_ATTACHMENT0 + write_slot);
		/* XXX we messed with the glDrawBuffer, this will reset the
		 * glDrawBuffers the next time we bind fb_write. */
		fb_write->dirty_flag = GPU_FB_DIRTY_DRAWBUFFER;
	}

	GLbitfield mask = convert_buffer_bits_to_gl(blit_buffers);

	glBlitFramebuffer(0, 0, fb_read->width, fb_read->height,
	                  0, 0, fb_write->width, fb_write->height,
	                  mask, GL_NEAREST);

	/* Restore previous framebuffer */
	if (fb_write->object == prev_fb) {
		GPU_framebuffer_bind(fb_write); /* To update drawbuffers */
	}
	else {
		glBindFramebuffer(GL_FRAMEBUFFER, prev_fb);
		gpu_framebuffer_current_set(prev_fb);
	}
}

/**
 * Use this if you need to custom downsample your texture and use the previous mip level as input.
 * This function only takes care of the correct texture handling. It execute the callback for each texture level.
 **/
void GPU_framebuffer_recursive_downsample(
        GPUFrameBuffer *fb, int max_lvl,
        void (*callback)(void *userData, int level), void *userData)
{
	/* Framebuffer must be up to date and bound. This simplify this function. */
	if (gpu_framebuffer_current_get() != fb->object || fb->dirty_flag != 0 || fb->object == 0) {
		GPU_framebuffer_bind(fb);
	}
	/* HACK: We make the framebuffer appear not bound in order to
	 * not trigger any error in GPU_texture_bind().  */
	GLuint prev_fb = gpu_framebuffer_current_get();
	gpu_framebuffer_current_set(0);

	int i;
	int current_dim[2] = {fb->width, fb->height};
	for (i = 1; i < max_lvl + 1; i++) {
		/* calculate next viewport size */
		current_dim[0] = max_ii(current_dim[0] / 2, 1);
		current_dim[1] = max_ii(current_dim[1] / 2, 1);

		for (GPUAttachmentType type = 0; type < GPU_FB_MAX_ATTACHEMENT; ++type) {
			if (fb->attachments[type].tex != NULL) {
				/* bind next level for rendering but first restrict fetches only to previous level */
				GPUTexture *tex = fb->attachments[type].tex;
				GPU_texture_bind(tex, 0);
				glTexParameteri(GPU_texture_target(tex), GL_TEXTURE_BASE_LEVEL, i - 1);
				glTexParameteri(GPU_texture_target(tex), GL_TEXTURE_MAX_LEVEL, i - 1);
				GPU_texture_unbind(tex);
				/* copy attachment and replace miplevel. */
				GPUAttachment attachment = fb->attachments[type];
				attachment.mip = i;
				gpu_framebuffer_attachment_attach(&attachment, type);
			}
		}

		BLI_assert(GL_FRAMEBUFFER_COMPLETE == glCheckFramebufferStatus(GL_FRAMEBUFFER));

		glViewport(0, 0, current_dim[0], current_dim[1]);
		callback(userData, i);

		if (current_dim[0] == 1 && current_dim[1] == 1)
			break;
	}

	for (GPUAttachmentType type = 0; type < GPU_FB_MAX_ATTACHEMENT; ++type) {
		if (fb->attachments[type].tex != NULL) {
			/* reset mipmap level range */
			GPUTexture *tex = fb->attachments[type].tex;
			GPU_texture_bind(tex, 0);
			glTexParameteri(GPU_texture_target(tex), GL_TEXTURE_BASE_LEVEL, 0);
			glTexParameteri(GPU_texture_target(tex), GL_TEXTURE_MAX_LEVEL, i - 1);
			GPU_texture_unbind(tex);
			/* Reattach original level */
			/* NOTE: This is not necessary but this makes the FBO config
			 *       remain in sync with the GPUFrameBuffer config. */
			gpu_framebuffer_attachment_attach(&fb->attachments[type], type);
		}
	}

	gpu_framebuffer_current_set(prev_fb);
}

/* GPUOffScreen */

struct GPUOffScreen {
	GPUFrameBuffer *fb;
	GPUTexture *color;
	GPUTexture *depth;
};

GPUOffScreen *GPU_offscreen_create(int width, int height, int samples, bool depth, bool high_bitdepth, char err_out[256])
{
	GPUOffScreen *ofs;

	ofs = MEM_callocN(sizeof(GPUOffScreen), "GPUOffScreen");

	ofs->color = GPU_texture_create_2D_multisample(width, height,
	        (high_bitdepth) ? GPU_RGBA16F : GPU_RGBA8, NULL, samples, err_out);

	if (depth) {
		ofs->depth = GPU_texture_create_2D_multisample(width, height, GPU_DEPTH24_STENCIL8, NULL, samples, err_out);
	}

	if ((depth && !ofs->depth) || !ofs->color) {
		GPU_offscreen_free(ofs);
		return NULL;
	}

	gpuPushAttrib(GPU_VIEWPORT_BIT);

	GPU_framebuffer_ensure_config(&ofs->fb, {
		GPU_ATTACHMENT_TEXTURE(ofs->depth),
		GPU_ATTACHMENT_TEXTURE(ofs->color)
	});

	/* check validity at the very end! */
	if (!GPU_framebuffer_check_valid(ofs->fb, err_out)) {
		GPU_offscreen_free(ofs);
		gpuPopAttrib();
		return NULL;
	}

	GPU_framebuffer_restore();

	gpuPopAttrib();

	return ofs;
}

void GPU_offscreen_free(GPUOffScreen *ofs)
{
	if (ofs->fb)
		GPU_framebuffer_free(ofs->fb);
	if (ofs->color)
		GPU_texture_free(ofs->color);
	if (ofs->depth)
		GPU_texture_free(ofs->depth);

	MEM_freeN(ofs);
}

void GPU_offscreen_bind(GPUOffScreen *ofs, bool save)
{
	if (save) {
		gpuPushAttrib(GPU_SCISSOR_BIT | GPU_VIEWPORT_BIT);
	}
	glDisable(GL_SCISSOR_TEST);
	GPU_framebuffer_bind(ofs->fb);
}

void GPU_offscreen_unbind(GPUOffScreen *UNUSED(ofs), bool restore)
{
	GPU_framebuffer_restore();
	if (restore) {
		gpuPopAttrib();
	}
}

void GPU_offscreen_draw_to_screen(GPUOffScreen *ofs, int x, int y)
{
	const int w = GPU_texture_width(ofs->color);
	const int h = GPU_texture_height(ofs->color);

	glBindFramebuffer(GL_READ_FRAMEBUFFER, ofs->fb->object);
	GLenum status = glCheckFramebufferStatus(GL_READ_FRAMEBUFFER);

	if (status == GL_FRAMEBUFFER_COMPLETE) {
		glBlitFramebuffer(0, 0, w, h, x, y, x + w, y + h, GL_COLOR_BUFFER_BIT, GL_NEAREST);
	}
	else {
		gpu_print_framebuffer_error(status, NULL);
	}

	glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
}

void GPU_offscreen_read_pixels(GPUOffScreen *ofs, int type, void *pixels)
{
	const int w = GPU_texture_width(ofs->color);
	const int h = GPU_texture_height(ofs->color);

	BLI_assert(type == GL_UNSIGNED_BYTE || type == GL_FLOAT);

	if (GPU_texture_target(ofs->color) == GL_TEXTURE_2D_MULTISAMPLE) {
		/* For a multi-sample texture,
		 * we need to create an intermediate buffer to blit to,
		 * before its copied using 'glReadPixels' */
		GLuint fbo_blit = 0;
		GLuint tex_blit = 0;

		/* create texture for new 'fbo_blit' */
		glGenTextures(1, &tex_blit);
		glBindTexture(GL_TEXTURE_2D, tex_blit);
		glTexImage2D(GL_TEXTURE_2D, 0, (type == GL_FLOAT) ? GL_RGBA16F : GL_RGBA8,
		             w, h, 0, GL_RGBA, type, 0);

		/* write into new single-sample buffer */
		glGenFramebuffers(1, &fbo_blit);
		glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo_blit);
		glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
		                       GL_TEXTURE_2D, tex_blit, 0);

		GLenum status = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER);
		if (status != GL_FRAMEBUFFER_COMPLETE) {
			goto finally;
		}

		/* perform the copy */
		glBlitFramebuffer(0, 0, w, h, 0, 0, w, h, GL_COLOR_BUFFER_BIT, GL_NEAREST);

		/* read the results */
		glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo_blit);
		glReadPixels(0, 0, w, h, GL_RGBA, type, pixels);

		/* restore the original frame-bufer */
		glBindFramebuffer(GL_FRAMEBUFFER, ofs->fb->object);

finally:
		/* cleanup */
		glDeleteTextures(1, &tex_blit);
		glDeleteFramebuffers(1, &fbo_blit);
	}
	else {
		glReadPixels(0, 0, w, h, GL_RGBA, type, pixels);
	}
}

int GPU_offscreen_width(const GPUOffScreen *ofs)
{
	return GPU_texture_width(ofs->color);
}

int GPU_offscreen_height(const GPUOffScreen *ofs)
{
	return GPU_texture_height(ofs->color);
}

GPUTexture *GPU_offscreen_color_texture(const GPUOffScreen *ofs)
{
	return ofs->color;
}

/* only to be used by viewport code! */
void GPU_offscreen_viewport_data_get(
        GPUOffScreen *ofs,
        GPUFrameBuffer **r_fb, GPUTexture **r_color, GPUTexture **r_depth)
{
	*r_fb = ofs->fb;
	*r_color = ofs->color;
	*r_depth = ofs->depth;
}

void GPU_clear_color(float red, float green, float blue, float alpha)
{
	glClearColor(red, green, blue, alpha);
}

void GPU_clear(GPUFrameBufferBits flags)
{
	glClear(convert_buffer_bits_to_gl(flags));
}