/*************************************************************************/
/*  renderer_scene_occlusion_cull.cpp                                    */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
/*                      https://godotengine.org                          */
/*************************************************************************/
/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
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/*************************************************************************/

#include "renderer_scene_occlusion_cull.h"

RendererSceneOcclusionCull *RendererSceneOcclusionCull::singleton = nullptr;

const Vector3 RendererSceneOcclusionCull::HZBuffer::corners[8] = {
	Vector3(0, 0, 0),
	Vector3(0, 0, 1),
	Vector3(0, 1, 0),
	Vector3(0, 1, 1),
	Vector3(1, 0, 0),
	Vector3(1, 0, 1),
	Vector3(1, 1, 0),
	Vector3(1, 1, 1)
};

bool RendererSceneOcclusionCull::HZBuffer::is_empty() const {
	return sizes.is_empty();
}

void RendererSceneOcclusionCull::HZBuffer::clear() {
	if (sizes.is_empty()) {
		return; // Already cleared
	}

	data.clear();
	sizes.clear();
	mips.clear();

	debug_data.clear();
	if (debug_image.is_valid()) {
		debug_image.unref();
	}
	RS::get_singleton()->free(debug_texture);
}

void RendererSceneOcclusionCull::HZBuffer::resize(const Size2i &p_size) {
	if (p_size == Size2i()) {
		clear();
		return;
	}

	if (!sizes.is_empty() && p_size == sizes[0]) {
		return; // Size didn't change
	}

	int mip_count = 0;
	int data_size = 0;
	int w = p_size.x;
	int h = p_size.y;

	while (true) {
		data_size += h * w;

		w = MAX(1, w >> 1);
		h = MAX(1, h >> 1);

		mip_count++;

		if (w == 1U && h == 1U) {
			data_size += 1U;
			mip_count++;
			break;
		}
	}

	data.resize(data_size);
	mips.resize(mip_count);
	sizes.resize(mip_count);

	w = p_size.x;
	h = p_size.y;
	float *ptr = data.ptr();

	for (int i = 0; i < mip_count; i++) {
		sizes[i] = Size2i(w, h);
		mips[i] = ptr;

		ptr = &ptr[w * h];
		w = MAX(1, w >> 1);
		h = MAX(1, h >> 1);
	}

	for (int i = 0; i < data_size; i++) {
		data[i] = FLT_MAX;
	}

	debug_data.resize(sizes[0].x * sizes[0].y);
	if (debug_texture.is_valid()) {
		RS::get_singleton()->free(debug_texture);
		debug_texture = RID();
	}
}

void RendererSceneOcclusionCull::HZBuffer::update_mips() {
	if (sizes.is_empty()) {
		return;
	}

	for (uint32_t mip = 1; mip < mips.size(); mip++) {
		for (int y = 0; y < sizes[mip].y; y++) {
			for (int x = 0; x < sizes[mip].x; x++) {
				int prev_x = x * 2;
				int prev_y = y * 2;

				int prev_w = sizes[mip - 1].width;
				int prev_h = sizes[mip - 1].height;

				bool odd_w = (prev_w % 2) != 0;
				bool odd_h = (prev_h % 2) != 0;

#define CHECK_OFFSET(xx, yy) max_depth = MAX(max_depth, mips[mip - 1][MIN(prev_h - 1, prev_y + (yy)) * prev_w + MIN(prev_w - 1, prev_x + (xx))])

				float max_depth = mips[mip - 1][prev_y * sizes[mip - 1].x + prev_x];
				CHECK_OFFSET(0, 1);
				CHECK_OFFSET(1, 0);
				CHECK_OFFSET(1, 1);

				if (odd_w) {
					CHECK_OFFSET(2, 0);
					CHECK_OFFSET(2, 1);
				}

				if (odd_h) {
					CHECK_OFFSET(0, 2);
					CHECK_OFFSET(1, 2);
				}

				if (odd_w && odd_h) {
					CHECK_OFFSET(2, 2);
				}

				mips[mip][y * sizes[mip].x + x] = max_depth;
#undef CHECK_OFFSET
			}
		}
	}
}

RID RendererSceneOcclusionCull::HZBuffer::get_debug_texture() {
	if (sizes.is_empty() || sizes[0] == Size2i()) {
		return RID();
	}

	if (debug_image.is_null()) {
		debug_image.instantiate();
	}

	unsigned char *ptrw = debug_data.ptrw();
	for (int i = 0; i < debug_data.size(); i++) {
		ptrw[i] = MIN(mips[0][i] / debug_tex_range, 1.0) * 255;
	}

	debug_image->set_data(sizes[0].x, sizes[0].y, false, Image::FORMAT_L8, debug_data);

	if (debug_texture.is_null()) {
		debug_texture = RS::get_singleton()->texture_2d_create(debug_image);
	} else {
		RenderingServer::get_singleton()->texture_2d_update(debug_texture, debug_image);
	}

	return debug_texture;
}