src/gl/compiler.cpp

/*
 *  LDForge: LDraw parts authoring CAD
 *  Copyright (C) 2013 - 2018 Teemu Piippo
 *
 *  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 3 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, see <http://www.gnu.org/licenses/>.
 */

#define GL_GLEXT_PROTOTYPES
#include <GL/glu.h>
#include <GL/glext.h>
#include <QMessageBox>
#include "gl/compiler.h"
#include "documentmanager.h"
#include "invert.h"
#include "ring.h"

constexpr char VERTEX_SHADER_SOURCE[] = R"(
#version 330 core

layout(location=0) in vec3 position;
layout(location=1) in vec4 color;
layout(location=2) in vec3 normal;
layout(location=3) in int id;
layout(location=4) in int selected;
out vec4 vColor;
out vec3 vFragPos;
out vec3 vNormal;
uniform mat4 modelMatrix;
uniform mat4 viewMatrix;
uniform mat4 projectionMatrix;
uniform int fragmentStyle;
uniform vec3 selectedColor;
uniform int highlighted;

const int FRAGSTYLE_Normal = 0;
const int FRAGSTYLE_BfcGreen = 1;
const int FRAGSTYLE_BfcRed = 2;
const int FRAGSTYLE_Random = 3;
const int FRAGSTYLE_Id = 4;
const int FRAGSTYLE_Black = 5;

void main()
{
	mat3 normalMatrix = transpose(inverse(mat3(modelMatrix)));
	vNormal = normalize(normalMatrix * normal);
	if (fragmentStyle == FRAGSTYLE_Id)
	{
		/* Calculate a color based from this index. This method caters for
		 * 16777216 objects. I don't think that will be exceeded anytime soon.
		 */
		int r = (id / 0x10000) % 0x100;
		int g = (id / 0x100) % 0x100;
		int b = id % 0x100;
		vColor = vec4(r / 255.0, g / 255.0, b / 255.0, 1.0);
	}
	else if (selected == 1)
	{
		vColor = vec4(selectedColor, 1.0);
	}
	else
	{
		if (fragmentStyle == FRAGSTYLE_BfcGreen)
		{
			vColor = vec4(0.2, 0.9, 0.2, 1.0);
		}
		else if (fragmentStyle == FRAGSTYLE_BfcRed)
		{
			vColor = vec4(0.9, 0.2, 0.2, 1.0);
		}
		else if (fragmentStyle == FRAGSTYLE_Black)
		{
			vColor = vec4(0.0, 0.0, 0.0, 1.0);
		}
		else
		{
			vColor = color;
		}
		if (highlighted == id)
		{
			vColor = (vColor + vec4(selectedColor, 1.0) * 0.6) / 1.6;
		}
	}

	vFragPos = vec3(modelMatrix * vec4(position, 1.0));
	gl_Position = projectionMatrix * viewMatrix * vec4(vFragPos, 1.0);
}
)";

constexpr char FRAGMENT_SHADER_SOURCE[] = R"(
#version 330 core

in vec4 vColor;
in vec3 vFragPos;
in vec3 vNormal;
out vec4 fColor;
const vec3 lightPos = vec3(0.5, 0.5, 0.5);
const vec4 lightColor = vec4(1.0, 1.0, 1.0, 1.0);
const float ambientStrength = 0.7;
uniform bool useLighting;

void main()
{
	if (useLighting)
	{
		vec4 ambient = ambientStrength * lightColor;
		vec3 lightDirection = normalize(lightPos - vFragPos);
		vec4 diffuse = max(dot(vNormal, lightDirection), 0.0) * lightColor;
		fColor = (ambient + diffuse) * vColor;
	}
	else
	{
		fColor = vColor;
	}
}
)";

template<typename Fn>
constexpr void pointsToRender(const PolygonElement& element, Fn func)
{
	visitPolygon<void>(
		[&func](const LineSegment& edge)
		{
			func(edge.p1, glm::vec3{});
			func(edge.p2, glm::vec3{});
		},
		[&func](const Triangle& tri)
		{
			func(tri.p1, normalVector({tri.p3, tri.p1, tri.p2}));
			func(tri.p2, normalVector({tri.p1, tri.p2, tri.p3}));
			func(tri.p3, normalVector({tri.p2, tri.p3, tri.p1}));
		},
		[&func](const Quadrilateral& quad)
		{
			func(quad.p1, normalVector({quad.p4, quad.p1, quad.p2}));
			func(quad.p2, normalVector({quad.p1, quad.p2, quad.p3}));
			func(quad.p3, normalVector({quad.p2, quad.p3, quad.p4}));
			func(quad.p4, normalVector({quad.p3, quad.p4, quad.p1}));
		},
		[&func](const ConditionalEdge& cedge)
		{
			func(cedge.p1, glm::vec3{});
			func(cedge.p2, glm::vec3{});
		},
		element);
}

void gl::buildShaders(
	QOpenGLShaderProgram* shaderProgram,
	const char* vertexShaderSource,
	const char* fragmentShaderSource)
{
	shaderProgram->create();
	const bool vertexShaderCompiled = shaderProgram->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
	QString log;
	if (not vertexShaderCompiled)
	{
		log += "\n" + QObject::tr("Vertex shader:") + "\n" + shaderProgram->log();
	}
	const bool fragmentShaderCompiled = shaderProgram->addShaderFromSourceCode(
		QOpenGLShader::Fragment,
		fragmentShaderSource);
	if (not fragmentShaderCompiled)
	{
		log += "\n" + QObject::tr("Fragment shader:") + "\n" + shaderProgram->log();
	}
	if (not vertexShaderCompiled or not fragmentShaderCompiled)
	{
		QMessageBox::critical(
			nullptr,
			QObject::tr("Shader compile error"),
			QObject::tr("Could not compile shaders.") + "\n" + log);
		std::exit(-1);
	}
	const bool linkSuccessful = shaderProgram->link();
	if (not linkSuccessful)
	{
		QMessageBox::critical(
			nullptr,
			QObject::tr("Shader link error"),
			QObject::tr("Could not link shaders: %1").arg(shaderProgram->log())
		);
	}
}

void gl::initializeModelShaders(gl::ModelShaders *modelShaders)
{
	if (not modelShaders->initialized) {
		for (auto& shader : modelShaders->shaderObjects) {
			shader.program = std::make_unique<QOpenGLShaderProgram>();
			gl::buildShaders(shader.program.get(), VERTEX_SHADER_SOURCE, FRAGMENT_SHADER_SOURCE);
			shader.program->bind();
			shader.buffer.create();
			shader.buffer.bind();
			shader.buffer.setUsagePattern(QOpenGLBuffer::DynamicDraw);
			shader.vertexArray.create();
			shader.vertexArray.bind();
			for (int k : {0, 1, 2, 3, 4}) {
				shader.program->enableAttributeArray(k);
			}
			using Vertex = ModelShaders::Vertex;
			constexpr int stride = sizeof(Vertex);
			shader.program->setAttributeBuffer(0, GL_FLOAT, offsetof(Vertex, position), 3, stride);
			shader.program->setAttributeBuffer(1, GL_FLOAT, offsetof(Vertex, color), 4, stride);
			shader.program->setAttributeBuffer(2, GL_FLOAT, offsetof(Vertex, normal), 3, stride);
			glVertexAttribIPointer(3, 1, GL_INT, stride, reinterpret_cast<void*>(offsetof(Vertex, id)));
			glVertexAttribIPointer(4, 1, GL_INT, stride, reinterpret_cast<void*>(offsetof(Vertex, selected)));
			shader.vertexArray.release();
			shader.buffer.release();
			shader.program->release();
		}
		modelShaders->initialized = true;
	}
}

static constexpr gl::ArrayClass classifyPolygon(const PolygonElement& element)
{
	return visitPolygon<gl::ArrayClass>(
		[](const LineSegment&) { return gl::ArrayClass::Lines; },
		[](const Triangle&) { return gl::ArrayClass::Triangles; },
		[](const Quadrilateral&) { return gl::ArrayClass::Quads; },
		[](const ConditionalEdge&) { return gl::ArrayClass::ConditionalLines; },
		element);
}

template<typename Fn>
void iterateModelPolygons(Model* model, DocumentManager* context, Fn&& fn)
{
	PolygonCache* cache = findPolygonCacheForModel(model, context);
	if (cache != nullptr) {
		const PolygonCache::vector_type* polygons = getCachedPolygons(cache, model, context);
		for (const WithId<PolygonElement>& polygon : *polygons) {
			fn(polygon);
		}
	}
}

static QColor getColorForPolygon(
	const PolygonElement& polygon,
	const gl::RenderPreferences& preferences,
	const ColorTable& colorTable)
{
	QColor color;
	// For normal colors, use the polygon's color.
	if (polygon.color == MAIN_COLOR)
	{
		color = preferences.mainColor;
	}
	else if (polygon.color == EDGE_COLOR)
	{
		// Edge color is black, unless we have a dark background, in which case lines need to be bright.
		color = luma(preferences.backgroundColor) > (40.0 / 256.0) ? Qt::black : Qt::white;
	}
	else
	{
		// Not main or edge color, use the polygon's color as is.
		color = colorFace(polygon.color, colorTable).value_or(Qt::black);
	}
	return color;
}

/**
 * @brief Computes the minimum bounding box for a model
 */
BoundingBox gl::boundingBoxForModel(Model* model, DocumentManager* context)
{
	BoundingBox result = emptyBoundingBox;
	iterateModelPolygons(model, context, [&](const PolygonElement& polygon)
	{
		visitPoints([&result](const glm::vec3& p) {
			addPointToBox(result, p);
		}, polygon);
	});
	return result;
}

/**
 * @brief gl::build Creates GL vertices for objects in the model and buffers them to shaders.
 */
void gl::build(
	gl::ModelShaders* shaders,
	Model* model,
	const ColorTable& colorTable,
	DocumentManager* context,
	const gl::RenderPreferences& preferences)
{
	for (gl::ModelShaders::ShaderObject& shader : shaders->shaderObjects) {
		shader.cachedData.clear();
	}
	iterateModelPolygons(model, context, [&](const WithId<PolygonElement>& polygon)
	{
		const int index = static_cast<int>(classifyPolygon(polygon));
		std::vector<gl::ModelShaders::Vertex>& vertexBuffer = shaders->shaderObjects[index].cachedData;
		const QColor color = getColorForPolygon(polygon, preferences, colorTable);
		pointsToRender(polygon, [&](const glm::vec3& point, const glm::vec3& normal){
			gl::ModelShaders::Vertex& vertex = vertexBuffer.emplace_back();
			vertex.position = point;
			vertex.normal = normal;
			vertex.color = glm::vec4{color.redF(), color.greenF(), color.blueF(), color.alphaF()};
			vertex.id = polygon.id.value;
		});
	});
	for (gl::ModelShaders::ShaderObject& shader : shaders->shaderObjects)
	{
		shader.vertexCount = shader.cachedData.size();
		shader.buffer.bind();
		const int bytes = static_cast<int>(shader.cachedData.size() * sizeof shader.cachedData[0]);
		shader.buffer.allocate(shader.cachedData.data(), bytes);
		shader.buffer.release();
	}
}

ModelId gl::idFromColor(const std::array<GLubyte, 3>& data)
{
	return {data[0] * std::int32_t{0x10000} + data[1] * std::int32_t{0x100} + data[2]};
}

void gl::bindModelShaderVertexArray(gl::ModelShaders* shaders, gl::ArrayClass arrayClass)
{
	ModelShaders::ShaderObject& shaderObject = shaders->shaderObjects[static_cast<int>(arrayClass)];
	shaderObject.vertexArray.bind();
	shaderObject.program->bind();
}

void gl::releaseModelShaderVertexArray(gl::ModelShaders* shaders, gl::ArrayClass arrayClass)
{
	ModelShaders::ShaderObject& shaderObject = shaders->shaderObjects[static_cast<int>(arrayClass)];
	shaderObject.program->release();
	shaderObject.vertexArray.release();
}

void gl::setModelShaderSelectedObjects(gl::ModelShaders* shaders, const QSet<ModelId> &ids)
{
	for (ModelShaders::ShaderObject& object : shaders->shaderObjects)
	{
		std::vector<ModelShaders::Vertex>& vector = object.cachedData;
		for (ModelShaders::Vertex& vertex : vector)
		{
			vertex.selected = (ids.contains({vertex.id})) ? 1 : 0;
		}
		const GLsizeiptr size = static_cast<int>(vector.size() * sizeof vector[0]);
		object.buffer.bind();
		glBufferSubData(GL_ARRAY_BUFFER, 0, size, vector.data());
		object.buffer.release();
	}
}

std::size_t gl::vertexCount(const gl::ModelShaders* shaders, const gl::ArrayClass arrayClass)
{
	return shaders->shaderObjects[static_cast<int>(arrayClass)].vertexCount;
}