blender-archive/source/blender/gpu/intern/gpu_select_pick.c

/*
 * ***** 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) 2017 Blender Foundation.
 * All rights reserved.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/gpu/intern/gpu_select_pick.c
 *  \ingroup gpu
 *
 * Custom select code for picking small regions (not efficient for large regions).
 * `gpu_select_pick_*` API.
 */
#include <string.h>
#include <stdlib.h>
#include <float.h>

#include "GPU_immediate.h"
#include "GPU_draw.h"
#include "GPU_select.h"
#include "GPU_extensions.h"
#include "GPU_glew.h"
 
#include "MEM_guardedalloc.h"

#include "BLI_rect.h"
#include "BLI_listbase.h"
#include "BLI_math_vector.h"
#include "BLI_utildefines.h"

#include "gpu_select_private.h"

#include "BLI_strict_flags.h"

/* #define DEBUG_PRINT */

/* Alloc number for depths */
#define ALLOC_DEPTHS 200

/* Z-depth of cleared depth buffer */
#define DEPTH_MAX 0xffffffff

/* ----------------------------------------------------------------------------
 * SubRectStride
 */

/* For looping over a sub-region of a rect, could be moved into 'rct.c'*/
typedef struct SubRectStride {
	uint start;     /* start here */
	uint span;      /* read these */
	uint span_len;  /* len times (read span 'len' times). */
	uint skip;      /* skip those */
} SubRectStride;

/* we may want to change back to float if uint isn't well supported */
typedef uint depth_t;

/**
 * Calculate values needed for looping over a sub-region (smaller buffer within a larger buffer).
 *
 * 'src' must be bigger than 'dst'.
 */
static void rect_subregion_stride_calc(const rcti *src, const rcti *dst, SubRectStride *r_sub)
{
	const int src_x = BLI_rcti_size_x(src);
	// const int src_y = BLI_rcti_size_y(src);
	const int dst_x = BLI_rcti_size_x(dst);
	const int dst_y = BLI_rcti_size_y(dst);
	const int x = dst->xmin - src->xmin;
	const int y = dst->ymin - src->ymin;

	BLI_assert(src->xmin <= dst->xmin && src->ymin <= dst->ymin &&
	           src->ymax >= dst->ymax && src->ymax >= dst->ymax);
	BLI_assert(x >= 0 && y >= 0);

	r_sub->start    = (uint)((src_x * y) + x);
	r_sub->span     = (uint)dst_x;
	r_sub->span_len = (uint)dst_y;
	r_sub->skip     = (uint)(src_x - dst_x);
}

/**
 * Ignore depth clearing as a change,
 * only check if its been changed _and_ filled in (ignore clearing since XRAY does this).
 */
BLI_INLINE bool depth_is_filled(const depth_t *prev, const depth_t *curr)
{
	return (*prev != *curr) && (*curr != DEPTH_MAX);
}

/* ----------------------------------------------------------------------------
 * DepthBufCache
 *
 * Result of reading glReadPixels,
 * use for both cache and non-cached storage.
 */

/* store result of glReadPixels */
typedef struct DepthBufCache {
	struct DepthBufCache *next, *prev;
	uint id;
	depth_t buf[0];
} DepthBufCache;

static DepthBufCache *depth_buf_malloc(uint rect_len)
{
	DepthBufCache *rect = MEM_mallocN(sizeof(DepthBufCache) + sizeof(depth_t) * rect_len, __func__);
	rect->id = SELECT_ID_NONE;
	return rect;
}

static bool depth_buf_rect_depth_any(
        const DepthBufCache *rect_depth,
        uint rect_len)
{
	const depth_t *curr = rect_depth->buf;
	for (uint i = 0; i < rect_len; i++, curr++) {
		if (*curr != DEPTH_MAX) {
			return true;
		}
	}
	return false;
}

static bool depth_buf_subrect_depth_any(
        const DepthBufCache *rect_depth,
        const SubRectStride *sub_rect)
{
	const depth_t *curr = rect_depth->buf + sub_rect->start;
	for (uint i = 0; i < sub_rect->span_len; i++) {
		const depth_t *curr_end = curr + sub_rect->span;
		for (; curr < curr_end; curr++, curr++) {
			if (*curr != DEPTH_MAX) {
				return true;
			}
		}
		curr += sub_rect->skip;
	}
	return false;
}

static bool depth_buf_rect_depth_any_filled(
        const DepthBufCache *rect_prev, const DepthBufCache *rect_curr,
        uint rect_len)
{
#if 0
	return memcmp(rect_depth_a->buf, rect_depth_b->buf, rect_len * sizeof(depth_t)) != 0;
#else
	const depth_t *prev = rect_prev->buf;
	const depth_t *curr = rect_curr->buf;
	for (uint i = 0; i < rect_len; i++, curr++, prev++) {
		if (depth_is_filled(prev, curr)) {
			return true;
		}
	}
	return false;
#endif
}

/**
 * Both buffers are the same size, just check if the sub-rect contains any differences.
 */
static bool depth_buf_subrect_depth_any_filled(
        const DepthBufCache *rect_src, const DepthBufCache *rect_dst,
        const SubRectStride *sub_rect)
{
	/* same as above but different rect sizes */
	const depth_t *prev = rect_src->buf + sub_rect->start;
	const depth_t *curr = rect_dst->buf + sub_rect->start;
	for (uint i = 0; i < sub_rect->span_len; i++) {
		const depth_t *curr_end = curr + sub_rect->span;
		for (; curr < curr_end; prev++, curr++) {
			if (depth_is_filled(prev, curr)) {
				return true;
			}
		}
		prev += sub_rect->skip;
		curr += sub_rect->skip;
	}
	return false;
}

/* ----------------------------------------------------------------------------
 * DepthID
 *
 * Internal structure for storing hits.
 */

typedef struct DepthID {
	uint id;
	depth_t depth;
} DepthID;

static int depth_id_cmp(const void *v1, const void *v2)
{
	const DepthID *d1 = v1, *d2 = v2;
	if (d1->id < d2->id) {
		return -1;
	}
	else if (d1->id > d2->id) {
		return 1;
	}
	else {
		return 0;
	}
}

static int depth_cmp(const void *v1, const void *v2)
{
	const DepthID *d1 = v1, *d2 = v2;
	if (d1->depth < d2->depth) {
		return -1;
	}
	else if (d1->depth > d2->depth) {
		return 1;
	}
	else {
		return 0;
	}
}

/* depth sorting */
typedef struct GPUPickState {
	/* cache on initialization */
	uint (*buffer)[4];

	/* buffer size (stores number of integers, for actual size multiply by sizeof integer)*/
	uint bufsize;
	/* mode of operation */
	char mode;

	/* OpenGL drawing, never use when (is_cached == true). */
	struct {
		/* The current depth, accumulated as we draw */
		DepthBufCache *rect_depth;
		/* Scratch buffer, avoid allocs every time (when not caching) */
		DepthBufCache *rect_depth_test;

		/* Pass to glReadPixels (x, y, w, h) */
		int clip_readpixels[4];

		/* Set after first draw */
		bool is_init;
		uint prev_id;
	} gl;

	/* src: data stored in 'cache' and 'gl',
	 * dst: use when cached region is smaller (where src -> dst isn't 1:1) */
	struct {
		rcti clip_rect;
		uint rect_len;
	} src, dst;

	/* Store cache between `GPU_select_cache_begin/end` */
	bool use_cache;
	bool is_cached;
	struct {
		/* Cleanup used for iterating over both source and destination buffers:
		 * src.clip_rect -> dst.clip_rect */
		SubRectStride sub_rect;

		/* List of DepthBufCache, sized of 'src.clip_rect' */
		ListBase bufs;
	} cache;

	/* Pickign methods */
	union {
		/* GPU_SELECT_PICK_ALL */
		struct {
			DepthID *hits;
			uint hits_len;
			uint hits_len_alloc;
		} all;

		/* GPU_SELECT_PICK_NEAREST */
		struct {
			uint *rect_id;
		} nearest;
	};
} GPUPickState;


static GPUPickState g_pick_state = {0};

void gpu_select_pick_begin(
        uint (*buffer)[4], uint bufsize,
        const rcti *input, char mode)
{
	GPUPickState *ps = &g_pick_state;

#ifdef DEBUG_PRINT
	printf("%s: mode=%d, use_cache=%d, is_cache=%d\n", __func__, mode, ps->use_cache, ps->is_cached);
#endif

	ps->bufsize = bufsize;
	ps->buffer = buffer;
	ps->mode = mode;

	const uint rect_len = (uint)(BLI_rcti_size_x(input) * BLI_rcti_size_y(input));
	ps->dst.clip_rect = *input;
	ps->dst.rect_len = rect_len;

	/* Restrict OpenGL operations for when we don't have cache */
	if (ps->is_cached == false) {
		gpuPushAttrib(GPU_DEPTH_BUFFER_BIT | GPU_VIEWPORT_BIT);

		/* disable writing to the framebuffer */
		glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);

		glEnable(GL_DEPTH_TEST);
		glDepthMask(GL_TRUE);

		if (mode == GPU_SELECT_PICK_ALL) {
			/* Note that other depth settings (such as #GL_LEQUAL) work too,
			 * since the depth is always cleared.
			 * Noting this for cases when depth picking is used where drawing calls change depth settings. */
			glDepthFunc(GL_ALWAYS);
		}
		else {
			glDepthFunc(GL_LEQUAL);
		}

		float viewport[4];
		glGetFloatv(GL_SCISSOR_BOX, viewport);

		ps->src.clip_rect = *input;
		ps->src.rect_len = rect_len;

		ps->gl.clip_readpixels[0] = (int)viewport[0];
		ps->gl.clip_readpixels[1] = (int)viewport[1];
		ps->gl.clip_readpixels[2] = BLI_rcti_size_x(&ps->src.clip_rect);
		ps->gl.clip_readpixels[3] = BLI_rcti_size_y(&ps->src.clip_rect);

		glViewport(UNPACK4(ps->gl.clip_readpixels));

		/* It's possible we don't want to clear depth buffer,
		 * so existing elements are masked by current z-buffer. */
		glClear(GL_DEPTH_BUFFER_BIT);

		/* scratch buffer (read new values here) */
		ps->gl.rect_depth_test = depth_buf_malloc(rect_len);
		ps->gl.rect_depth = depth_buf_malloc(rect_len);

		/* set initial 'far' value */
#if 0
		glReadPixels(UNPACK4(ps->gl.clip_readpixels), GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, ps->gl.rect_depth->buf);
#else
		for (uint i = 0; i < rect_len; i++) {
			ps->gl.rect_depth->buf[i] = DEPTH_MAX;
		}
#endif

		ps->gl.is_init = false;
		ps->gl.prev_id = 0;
	}
	else {
		/* Using cache (ps->is_cached == true) */
		/* src.clip_rect -> dst.clip_rect */
		rect_subregion_stride_calc(&ps->src.clip_rect, &ps->dst.clip_rect, &ps->cache.sub_rect);
		BLI_assert(ps->gl.rect_depth == NULL);
		BLI_assert(ps->gl.rect_depth_test == NULL);
	}

	if (mode == GPU_SELECT_PICK_ALL) {
		ps->all.hits = MEM_mallocN(sizeof(*ps->all.hits) * ALLOC_DEPTHS, __func__);
		ps->all.hits_len = 0;
		ps->all.hits_len_alloc = ALLOC_DEPTHS;
	}
	else {
		/* Set to 0xff for SELECT_ID_NONE */
		ps->nearest.rect_id = MEM_mallocN(sizeof(uint) * ps->dst.rect_len, __func__);
		memset(ps->nearest.rect_id, 0xff, sizeof(uint) * ps->dst.rect_len);
	}
}

/**
 * Given 2x depths, we know are different - update the depth information
 * use for both cached/uncached depth buffers.
 */
static void gpu_select_load_id_pass_all(const DepthBufCache *rect_curr)
{
	GPUPickState *ps = &g_pick_state;
	const uint id = rect_curr->id;
	/* find the best depth for this pass and store in 'all.hits' */
	depth_t depth_best = DEPTH_MAX;

#define EVAL_TEST() \
	if (depth_best > *curr) { \
		depth_best = *curr; \
	} ((void)0)

	if (ps->is_cached == false) {
		const depth_t *curr = rect_curr->buf;
		BLI_assert(ps->src.rect_len == ps->dst.rect_len);
		const uint rect_len = ps->src.rect_len;
		for (uint i = 0; i < rect_len; i++, curr++) {
			EVAL_TEST();
		}
	}
	else {
		/* same as above but different rect sizes */
		const depth_t *curr = rect_curr->buf + ps->cache.sub_rect.start;
		for (uint i = 0; i < ps->cache.sub_rect.span_len; i++) {
			const depth_t *curr_end = curr + ps->cache.sub_rect.span;
			for (; curr < curr_end; curr++) {
				EVAL_TEST();
			}
			curr += ps->cache.sub_rect.skip;
		}
	}

#undef EVAL_TEST

	/* ensure enough space */
	if (UNLIKELY(ps->all.hits_len == ps->all.hits_len_alloc)) {
		ps->all.hits_len_alloc += ALLOC_DEPTHS;
		ps->all.hits = MEM_reallocN(ps->all.hits, ps->all.hits_len_alloc * sizeof(*ps->all.hits));
	}
	DepthID *d = &ps->all.hits[ps->all.hits_len++];
	d->id = id;
	d->depth = depth_best;
}

static void gpu_select_load_id_pass_nearest(const DepthBufCache *rect_prev, const DepthBufCache *rect_curr)
{
	GPUPickState *ps = &g_pick_state;
	const uint id = rect_curr->id;
	/* keep track each pixels ID in 'nearest.rect_id' */
	if (id != SELECT_ID_NONE) {
		uint *id_ptr = ps->nearest.rect_id;

		/* Check against DEPTH_MAX because XRAY will clear the buffer,
		 * so previously set values will become unset.
		 * In this case just leave those id's left as-is. */
#define EVAL_TEST() \
		if (depth_is_filled(prev, curr)) { \
			*id_ptr = id; \
		} ((void)0)

		if (ps->is_cached == false) {
			const depth_t *prev = rect_prev->buf;
			const depth_t *curr = rect_curr->buf;
			BLI_assert(ps->src.rect_len == ps->dst.rect_len);
			const uint rect_len = ps->src.rect_len;
			for (uint i = 0; i < rect_len; i++, curr++, prev++, id_ptr++) {
				EVAL_TEST();
			}
		}
		else {
			/* same as above but different rect sizes */
			const depth_t *prev = rect_prev->buf + ps->cache.sub_rect.start;
			const depth_t *curr = rect_curr->buf + ps->cache.sub_rect.start;
			for (uint i = 0; i < ps->cache.sub_rect.span_len; i++) {
				const depth_t *curr_end = curr + ps->cache.sub_rect.span;
				for (; curr < curr_end; prev++, curr++, id_ptr++) {
					EVAL_TEST();
				}
				prev += ps->cache.sub_rect.skip;
				curr += ps->cache.sub_rect.skip;
			}
		}

#undef EVAL_TEST
	}
}


bool gpu_select_pick_load_id(uint id)
{
	GPUPickState *ps = &g_pick_state;
	if (ps->gl.is_init) {
		const uint rect_len = ps->src.rect_len;
		glReadPixels(UNPACK4(ps->gl.clip_readpixels), GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, ps->gl.rect_depth_test->buf);
		/* perform initial check since most cases the array remains unchanged  */

		bool do_pass = false;
		if (g_pick_state.mode == GPU_SELECT_PICK_ALL) {
			if (depth_buf_rect_depth_any(ps->gl.rect_depth_test, rect_len)) {
				ps->gl.rect_depth_test->id = ps->gl.prev_id;
				gpu_select_load_id_pass_all(ps->gl.rect_depth_test);
				do_pass = true;
			}
		}
		else {
			if (depth_buf_rect_depth_any_filled(ps->gl.rect_depth, ps->gl.rect_depth_test, rect_len)) {
				ps->gl.rect_depth_test->id = ps->gl.prev_id;
				gpu_select_load_id_pass_nearest(ps->gl.rect_depth, ps->gl.rect_depth_test);
				do_pass = true;
			}
		}

		if (do_pass) {
			/* Store depth in cache */
			if (ps->use_cache) {
				BLI_addtail(&ps->cache.bufs, ps->gl.rect_depth);
				ps->gl.rect_depth = depth_buf_malloc(ps->src.rect_len);
			}

			SWAP(DepthBufCache *, ps->gl.rect_depth, ps->gl.rect_depth_test);

			if (g_pick_state.mode == GPU_SELECT_PICK_ALL) {
				/* we want new depths every time */
				glClear(GL_DEPTH_BUFFER_BIT);
			}
		}
	}

	ps->gl.is_init = true;
	ps->gl.prev_id = id;

	return true;
}

uint gpu_select_pick_end(void)
{
	GPUPickState *ps = &g_pick_state;

#ifdef DEBUG_PRINT
	printf("%s\n", __func__);
#endif

	if (ps->is_cached == false) {
		if (ps->gl.is_init) {
			/* force finishing last pass */
			gpu_select_pick_load_id(ps->gl.prev_id);
		}
		gpuPopAttrib();
		glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
	}

	/* assign but never free directly since it may be in cache */
	DepthBufCache *rect_depth_final;

	/* Store depth in cache */
	if (ps->use_cache && !ps->is_cached) {
		BLI_addtail(&ps->cache.bufs, ps->gl.rect_depth);
		ps->gl.rect_depth = NULL;
		rect_depth_final = ps->cache.bufs.last;
	}
	else if (ps->is_cached) {
		rect_depth_final = ps->cache.bufs.last;
	}
	else {
		/* common case, no cache */
		rect_depth_final = ps->gl.rect_depth;
	}

	uint maxhits = g_pick_state.bufsize;
	DepthID *depth_data;
	uint depth_data_len = 0;

	if (g_pick_state.mode == GPU_SELECT_PICK_ALL) {
		depth_data = ps->all.hits;
		depth_data_len = ps->all.hits_len;
		/* move ownership */
		ps->all.hits = NULL;
		ps->all.hits_len = 0;
		ps->all.hits_len_alloc = 0;
	}
	else {
		/* GPU_SELECT_PICK_NEAREST */

		/* Over alloc (unlikely we have as many depths as pixels) */
		uint depth_data_len_first_pass = 0;
		depth_data = MEM_mallocN(ps->dst.rect_len * sizeof(*depth_data), __func__);

		/* Partially de-duplicating copy,
		 * when contiguous ID's are found - update their closest depth.
		 * This isn't essential but means there is less data to sort. */

#define EVAL_TEST(i_src, i_dst) \
		{ \
			const uint id = ps->nearest.rect_id[i_dst]; \
			if (id != SELECT_ID_NONE) { \
				const depth_t depth = rect_depth_final->buf[i_src]; \
				if (depth_last == NULL || depth_last->id != id) { \
					DepthID *d = &depth_data[depth_data_len_first_pass++]; \
					d->id = id; \
					d->depth = depth; \
				} \
				else if (depth_last->depth > depth) { \
					depth_last->depth = depth; \
				} \
			} \
		} ((void)0)

		{
			DepthID *depth_last = NULL;
			if (ps->is_cached == false) {
				for (uint i = 0; i < ps->src.rect_len; i++) {
					EVAL_TEST(i, i);
				}
			}
			else {
				/* same as above but different rect sizes */
				uint i_src = ps->cache.sub_rect.start, i_dst = 0;
				for (uint j = 0; j < ps->cache.sub_rect.span_len; j++) {
					const uint i_src_end = i_src + ps->cache.sub_rect.span;
					for (; i_src < i_src_end; i_src++, i_dst++) {
						EVAL_TEST(i_src, i_dst);
					}
					i_src += ps->cache.sub_rect.skip;
				}
			}
		}

#undef EVAL_TEST

		qsort(depth_data, depth_data_len_first_pass, sizeof(DepthID), depth_id_cmp);

		/* Sort by ID's then keep the best depth for each ID */
		depth_data_len = 0;
		{
			DepthID *depth_last = NULL;
			for (uint i = 0; i < depth_data_len_first_pass; i++) {
				if (depth_last == NULL || depth_last->id != depth_data[i].id) {
					depth_last = &depth_data[depth_data_len++];
					*depth_last = depth_data[i];
				}
				else if (depth_last->depth > depth_data[i].depth) {
					depth_last->depth = depth_data[i].depth;
				}
			}
		}
	}

	/* Finally sort each unique (id, depth) pair by depth
	 * so the final hit-list is sorted by depth (nearest first) */
	uint hits = 0;

	if (depth_data_len > maxhits) {
		hits = (uint)-1;
	}
	else {
		/* leave sorting up to the caller */
		qsort(depth_data, depth_data_len, sizeof(DepthID), depth_cmp);

		for (uint i = 0; i < depth_data_len; i++) {
#ifdef DEBUG_PRINT
			printf("  hit: %u: depth %u\n", depth_data[i].id,  depth_data[i].depth);
#endif
			/* first 3 are dummy values */
			g_pick_state.buffer[hits][0] = 1;
			g_pick_state.buffer[hits][1] = 0x0;  /* depth_data[i].depth; */ /* unused */
			g_pick_state.buffer[hits][2] = 0x0;  /* z-far is currently never used. */
			g_pick_state.buffer[hits][3] = depth_data[i].id;
			hits++;
		}
		BLI_assert(hits < maxhits);
	}

	MEM_freeN(depth_data);

	MEM_SAFE_FREE(ps->gl.rect_depth);
	MEM_SAFE_FREE(ps->gl.rect_depth_test);

	if (g_pick_state.mode == GPU_SELECT_PICK_ALL) {
		/* 'hits' already freed as 'depth_data' */
	}
	else {
		MEM_freeN(ps->nearest.rect_id);
		ps->nearest.rect_id = NULL;
	}

	if (ps->use_cache) {
		ps->is_cached = true;
	}

	return hits;
}

/* ----------------------------------------------------------------------------
 * Caching
 *
 * Support multiple begin/end's reusing depth buffers.
 */

void gpu_select_pick_cache_begin(void)
{
	BLI_assert(g_pick_state.use_cache == false);
#ifdef DEBUG_PRINT
	printf("%s\n", __func__);
#endif
	g_pick_state.use_cache = true;
	g_pick_state.is_cached = false;
}

void gpu_select_pick_cache_end(void)
{
#ifdef DEBUG_PRINT
	printf("%s: with %d buffers\n", __func__, BLI_listbase_count(&g_pick_state.cache.bufs));
#endif
	g_pick_state.use_cache = false;
	g_pick_state.is_cached = false;

	BLI_freelistN(&g_pick_state.cache.bufs);
}

/* is drawing needed? */
bool gpu_select_pick_is_cached(void)
{
	return g_pick_state.is_cached;
}

void gpu_select_pick_cache_load_id(void)
{
	BLI_assert(g_pick_state.is_cached == true);
	GPUPickState *ps = &g_pick_state;
#ifdef DEBUG_PRINT
	printf("%s (building depth from cache)\n", __func__);
#endif
	for (DepthBufCache *rect_depth = ps->cache.bufs.first; rect_depth; rect_depth = rect_depth->next) {
		if (rect_depth->next != NULL) {
			/* we know the buffers differ, but this sub-region may not.
			 * double check before adding an id-pass */
			if (g_pick_state.mode == GPU_SELECT_PICK_ALL) {
				if (depth_buf_subrect_depth_any(rect_depth->next, &ps->cache.sub_rect)) {
					gpu_select_load_id_pass_all(rect_depth->next);
				}
			}
			else {
				if (depth_buf_subrect_depth_any_filled(rect_depth, rect_depth->next, &ps->cache.sub_rect)) {
					gpu_select_load_id_pass_nearest(rect_depth, rect_depth->next);
				}
			}
		}
	}
}