From d311a65e0c86aaec94f6d9a61d5f9b374f90aa5c Mon Sep 17 00:00:00 2001
From: LaG1924 <12997935+LaG1924@users.noreply.github.com>
Date: Sat, 4 Aug 2018 19:57:19 +0500
Subject: Implemented texture atlas

---
 src/TextureAtlas.cpp | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 src/TextureAtlas.cpp

(limited to 'src/TextureAtlas.cpp')

diff --git a/src/TextureAtlas.cpp b/src/TextureAtlas.cpp
new file mode 100644
index 0000000..23ab92d
--- /dev/null
+++ b/src/TextureAtlas.cpp
@@ -0,0 +1,104 @@
+#include "TextureAtlas.hpp"
+
+#define STB_RECT_PACK_IMPLEMENTATION
+
+#include <stb_rect_pack.h>
+#include <easylogging++.h>
+
+#include "Utility.hpp"
+
+TextureAtlas::TextureAtlas(std::vector<TextureData> &textures) {
+	LOG(INFO) << "Initializing texture atlas...";
+	LOG(INFO) << "Textures count: " << textures.size();
+
+	//Texture packing
+	const int textureSize = 1024;
+
+	std::vector<stbrp_rect> totalRects;
+	for (int i = 0; i < textures.size(); i++) {
+		stbrp_rect rect;
+		rect.id = i;
+		rect.x = 0;
+		rect.y = 0;
+		rect.w = textures[i].width;
+		rect.h = textures[i].height;
+		rect.was_packed = 0;
+		totalRects.push_back(rect);
+	}
+
+	textureCoords.resize(textures.size());
+
+	int layer = 0;
+	for (;;layer++) {
+		stbrp_context context;
+		std::vector<stbrp_node> nodes;
+		int nodesCount = textureSize * 2;
+		nodes.resize(nodesCount);
+		stbrp_init_target(&context, textureSize, textureSize, nodes.data(), nodesCount);
+
+		std::vector<stbrp_rect> rects;
+		for (const auto &it : totalRects) {
+			if (it.was_packed != 0)
+				continue;
+
+			rects.push_back(it);
+		}
+		stbrp_pack_rects(&context, rects.data(), rects.size());
+
+		int unpackedTextures = 0;
+		for (auto &it : rects) {
+			if (!it.was_packed) {
+				unpackedTextures++;
+				continue;
+			}
+			textureCoords[it.id].pixelX = it.x;
+			textureCoords[it.id].pixelY = it.y;
+			textureCoords[it.id].pixelW = it.w;
+			textureCoords[it.id].pixelH = it.h;
+			textureCoords[it.id].layer = layer;
+			textureCoords[it.id].x = (double)it.x / textureSize;
+			textureCoords[it.id].y = (double)it.y / textureSize;
+			textureCoords[it.id].w = (double)it.w / textureSize;
+			textureCoords[it.id].h = (double)it.h / textureSize;
+			totalRects[it.id].was_packed = 1;
+		}
+		if (unpackedTextures == 0)
+			break;
+	}
+	LOG(INFO) << "Texture atlas size is " << textureSize << "x" << textureSize << "x" << layer;
+
+	//OpenGL
+	int mipLevelCount = 1;
+
+	glGenTextures(1, &texture);
+	glBindTexture(GL_TEXTURE_2D_ARRAY, texture);
+	glTexStorage3D(GL_TEXTURE_2D_ARRAY, mipLevelCount, GL_RGBA8, textureSize, textureSize, layer+1);
+	glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+	glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+	glCheckError();
+
+	//Uploading texture data
+	for (int i = 0; i < textureCoords.size(); i++) {
+		size_t bytesPerLine = textureCoords[i].pixelW * 4;
+		for (int y = 0; y < textureCoords[i].pixelH / 2; y++) {
+			int invY = textureCoords[i].pixelH - y - 1;
+			unsigned char *src = textures[i].data.data() + y * bytesPerLine;
+			unsigned char *dst = textures[i].data.data() + invY * bytesPerLine;
+			for (int j = 0; j < bytesPerLine; j++) {
+				std::swap(*(src + j), *(dst + j));
+			}
+		}
+		glTexSubImage3D(GL_TEXTURE_2D_ARRAY, 0, textureCoords[i].pixelX, textureSize - textureCoords[i].pixelY - textureCoords[i].pixelH, textureCoords[i].layer,
+			textureCoords[i].pixelW, textureCoords[i].pixelH, 1, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8, textures[i].data.data());
+		glCheckError();
+	}
+
+	LOG(INFO) << "Texture atlas initialized";
+}
+
+TextureAtlas::~TextureAtlas() {
+	glDeleteTextures(1, &texture);
+}
-- 
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