src/gl/partrenderer.cpp

/*
 *  LDForge: LDraw parts authoring CAD
 *  Copyright (C) 2013 - 2020 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/>.
 */

#include <glm/ext/matrix_transform.hpp>
#include <glm/ext/matrix_clip_space.hpp>
#include <GL/glu.h>
#include <QMouseEvent>
#include <QMessageBox>
#include <QAbstractButton>
#include "geometry.h"
#include "partrenderer.h"
#include "model.h"

static constexpr double MIN_ZOOM = -3.0;
static constexpr double MAX_ZOOM = 3.0;
QOpenGLFunctions glfunc;

PartRenderer::PartRenderer(
	Model* model,
	DocumentManager* documents,
	const ldraw::ColorTable& colorTable,
	QWidget* parent) :
	QOpenGLWidget{parent},
	model{model},
	documents{documents},
	colorTable{colorTable}
{
	this->setMouseTracking(true);
	connect(model, &Model::rowsInserted, [&]{
		this->needBuild = true;
	});
	connect(model, &Model::rowsRemoved, [&]{ this->needBuild = true; });
}

PartRenderer::~PartRenderer()
{
}

static QVector3D calcQVector3DFromQColor(const QColor& color)
{
	return {
		toFloat(color.redF()),
		toFloat(color.greenF()),
		toFloat(color.blueF()),
	};
}

void PartRenderer::initializeGL()
{
	::glfunc.initializeOpenGLFunctions();
	if (glGetError() != GL_NO_ERROR)
	{
		abort();
	}
	gl::initializeModelShaders(&this->shaders);
	connect(this->model, &Model::dataChanged, this, &PartRenderer::build);
	this->initialized = true;
	this->modelQuaternion = glm::angleAxis(glm::radians(30.0f), glm::vec3{-1, 0, 0});
	this->modelQuaternion *= glm::angleAxis(glm::radians(225.0f), glm::vec3{-0, 1, 0});
	this->updateModelMatrix();
	this->updateViewMatrix();
	this->update();
}

void PartRenderer::resizeGL(int width, int height)
{
	this->viewportVector = {0, 0, width, height};
	glViewport(0, 0, width, height);
	this->projectionMatrix = glm::perspective(
		glm::radians(45.0f),
		static_cast<float>(width) / static_cast<float>(height),
		0.1f,
		10000.f);
	gl::setShaderUniformMatrix(&this->shaders, "projectionMatrix", this->projectionMatrix);
	Q_EMIT projectionMatrixChanged(this->projectionMatrix);
}

static constexpr GLenum getGlTypeForArrayClass(const gl::ArrayClass vboClass)
{
	switch (vboClass)
	{
	case gl::ArrayClass::Lines:
	case gl::ArrayClass::ConditionalLines:
		return GL_LINES;
	case gl::ArrayClass::Triangles:
		return GL_TRIANGLES;
	case gl::ArrayClass::Quads:
		return GL_QUADS;
	}
	throw std::runtime_error{"bad value for vboClass"};
}

void PartRenderer::paintGL()
{
	glEnable(GL_DEPTH_TEST);
	glShadeModel(GL_SMOOTH);
	this->renderScene();
}

void PartRenderer::renderScene()
{
	if (this->needBuild)
	{
		gl::build(&this->shaders, this->model, this->colorTable, this->documents, this->renderPreferences);
		this->boundingBox = gl::boundingBoxForModel(this->model, this->documents);
		this->needBuild = false;
	}
	this->checkForGLErrors();
	if (true
		and this->renderPreferences.lineAntiAliasing
		and this->renderPreferences.style != gl::RenderStyle::PickScene
	) {
		glEnable(GL_LINE_SMOOTH);
		glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
	}
	else {
		glDisable(GL_LINE_SMOOTH);
	}
	if (this->renderPreferences.style != gl::RenderStyle::PickScene)
	{
		const QColor& backgroundColor = this->renderPreferences.backgroundColor;
		glClearColor(
			static_cast<float>(backgroundColor.redF()),
			static_cast<float>(backgroundColor.greenF()),
			static_cast<float>(backgroundColor.blueF()),
			1.0f);
		gl::setShaderUniform(&this->shaders, "useLighting", GL_TRUE);
	}
	else
	{
		glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
		gl::setShaderUniform(&this->shaders, "useLighting", GL_FALSE);
	}
	this->checkForGLErrors();
	const QVector3D color = calcQVector3DFromQColor(this->renderPreferences.selectedColor);
	gl::setShaderUniform(&this->shaders, "selectedColor", color);
	gl::setShaderUniform(&this->shaders, "highlighted", this->highlighted.value);
	this->checkForGLErrors();
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_POLYGON_OFFSET_FILL);
	glPolygonOffset(1.0f, 1.0f);
	glLineWidth(this->renderPreferences.lineThickness);
	const auto renderAllArrays = [this](){
		// Lines need to be rendered last so that anti-aliasing does not interfere with polygon rendering.
		this->renderVao(gl::ArrayClass::Triangles);
		this->renderVao(gl::ArrayClass::Quads);
		this->renderVao(gl::ArrayClass::Lines);
	};
	switch (this->renderPreferences.style)
	{
	case gl::RenderStyle::Normal:
		this->setFragmentStyle(gl::FragmentStyle::Normal);
		renderAllArrays();
		break;
	case gl::RenderStyle::BfcRedGreen:
		glEnable(GL_CULL_FACE);
		glCullFace(GL_BACK);
		this->setFragmentStyle(gl::FragmentStyle::BfcGreen);
		renderVao(gl::ArrayClass::Triangles);
		renderVao(gl::ArrayClass::Quads);
		glCullFace(GL_FRONT);
		this->setFragmentStyle(gl::FragmentStyle::BfcRed);
		renderVao(gl::ArrayClass::Triangles);
		renderVao(gl::ArrayClass::Quads);
		glDisable(GL_CULL_FACE);
		this->setFragmentStyle(gl::FragmentStyle::Normal);
		renderVao(gl::ArrayClass::Lines);
		break;
	case gl::RenderStyle::RandomColors:
		this->setFragmentStyle(gl::FragmentStyle::RandomColors);
		renderAllArrays();
		break;
	case gl::RenderStyle::PickScene:
		glLineWidth(3.0f);
		this->setFragmentStyle(gl::FragmentStyle::Id);
		renderAllArrays();
		break;
	case gl::RenderStyle::VertexPickScene:
		glLineWidth(1.0f);
		this->setFragmentStyle(gl::FragmentStyle::Black);
		renderAllArrays();
		break;
	case gl::RenderStyle::Wireframe:
		glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
		this->setFragmentStyle(gl::FragmentStyle::Normal);
		renderAllArrays();
		break;
	}
	glDisable(GL_POLYGON_OFFSET_FILL);
}


void PartRenderer::updateViewMatrix()
{
	// I'm not quite sure why using the exponent function on the zoom factor causes linear zoom behavior
	const float modelDistance = longestMeasure(this->boundingBox);
	const double z  = 2.0 * std::exp(this->zoom) * (1 + static_cast<double>(modelDistance));
	this->viewMatrix = glm::lookAt(glm::vec3{0, 0, z}, {0, 0, 0}, {0, -1, 0});
	gl::setShaderUniformMatrix(&this->shaders, "viewMatrix", this->viewMatrix);
	Q_EMIT this->viewMatrixChanged(this->viewMatrix);
}

void PartRenderer::updateModelMatrix()
{
	this->modelMatrix = glm::mat4_cast(this->modelQuaternion);
	gl::setShaderUniformMatrix(&this->shaders, "modelMatrix", modelMatrix);
	Q_EMIT this->modelMatrixChanged(this->modelMatrix);
	this->update();
}

void PartRenderer::build()
{
	this->needBuild = true;
}

void PartRenderer::renderVao(const gl::ArrayClass arrayClass)
{
	gl::bindModelShaderVertexArray(&this->shaders, arrayClass);
	const std::size_t vertexCount = gl::vertexCount(&this->shaders, arrayClass);
	this->checkForGLErrors();
	glDrawArrays(getGlTypeForArrayClass(arrayClass), 0, static_cast<GLsizei>(vertexCount));
	this->checkForGLErrors();
	gl::releaseModelShaderVertexArray(&this->shaders, arrayClass);
	this->checkForGLErrors();
}

void PartRenderer::checkForGLErrors()
{
	gl::checkForGLErrors(this);
}

void gl::checkForGLErrors(QWidget* parent)
{
	GLenum glError;
	QStringList errors;
	while ((glError = glGetError()) != GL_NO_ERROR)
	{
		const QString glErrorString = QString::fromLatin1(reinterpret_cast<const char*>(gluErrorString(glError)));
		errors.append(glErrorString);
	}
	if (not errors.isEmpty())
	{
		QMessageBox box{parent};
		box.setIcon(QMessageBox::Critical);
		box.setText(QObject::tr("OpenGL error: %1").arg(errors.join("\n")));
		box.setWindowTitle(QObject::tr("OpenGL error"));
		box.setStandardButtons(QMessageBox::Close);
		box.button(QMessageBox::Close)->setText(QObject::tr("Damn it"));
		box.exec();
	}
}

void PartRenderer::mouseMoveEvent(QMouseEvent* event)
{
	const bool left = event->buttons() & Qt::LeftButton;
	const QPoint move = event->pos() - this->lastMousePosition;
	if (left and not move.isNull())
	{
		// q_x is the rotation of the brick along the vertical y-axis, because turning the
		// vertical axis causes horizontal (=x) rotation. Likewise q_y is the rotation of the
		// brick along the horizontal x-axis, which causes vertical rotation.
		const auto scalar = 0.006f;
		const float move_x = static_cast<float>(move.x());
		const float move_y = static_cast<float>(move.y());
		const glm::quat q_x = glm::angleAxis(scalar * move_x, glm::vec3{0, -1, 0});
		const glm::quat q_y = glm::angleAxis(scalar * move_y, glm::vec3{-1, 0, 0});
		this->modelQuaternion = q_x * q_y * this->modelQuaternion;
		this->updateModelMatrix();
	}
	this->lastMousePosition = event->pos();
}

void PartRenderer::wheelEvent(QWheelEvent* event)
{
	static constexpr double WHEEL_STEP = 1 / 1000.0;
	const double move = (-event->angleDelta().y()) * WHEEL_STEP;
	this->zoom = std::clamp(this->zoom + move, MIN_ZOOM, MAX_ZOOM);
	this->updateViewMatrix();
	this->update();
}

/**
 * @brief Converts the specified on the screen into the 3D world. The point is unprojected twice into 3D and the
 * intersection of the resulting line with the specified plane is returned. If the intersection point lies behind
 * the camera, no value is returned.
 * @param point 2D window co-ordinates to convert.
 * @param plane Plane to raycast against
 * @return world co-ordinates, or no value if the point is behind the camera.
 */
std::optional<glm::vec3> PartRenderer::screenToModelCoordinates(const QPoint& point, const geom::Plane& plane) const
{
	const geom::Line line = this->cameraLine(point);
	std::optional<glm::vec3> result;
	result = geom::linePlaneIntersection(line, plane, 0.01f);
	// If the point lies behind the camera, do not return a result.
	if (result.has_value() and glm::dot(line.direction, *result - line.anchor) < 0)
	{
		result.reset();
	}
	return result;
}

/**
 * @brief Converts the specified point to 2D window coordinates, with Y-coordinate inverted for Qt
 * @param point Point to unproject
 * @return screen coordinates
 */
QPointF PartRenderer::modelToScreenCoordinates(const glm::vec3& point) const
{
	const glm::vec3 projected = glm::project(
		point,
		this->viewMatrix * glm::mat4_cast(this->modelQuaternion),
		this->projectionMatrix,
		this->viewportVector);
	return toQPointF(glm::vec2{projected.x, this->height() - projected.y});
}

geom::Line<3> PartRenderer::cameraLine(const QPoint& point) const
{
	const glm::vec3 p1 = this->unproject({point.x(), point.y(), 0});
	const glm::vec3 p2 = this->unproject({point.x(), point.y(), 1});
	return geom::lineFromPoints(p1, p2);
}

/**
 * @brief Unprojects the specified window coordinates to model coordinates
 * @param win Window coordinates to project. Z-coordinate indicates depth
 * @return model coordinates
 */
glm::vec3 PartRenderer::unproject(const glm::vec3& win) const
{
	return glm::unProject(
		glm::vec3{win.x, this->height() - win.y, win.z},
		this->viewMatrix * glm::mat4_cast(this->modelQuaternion),
		this->projectionMatrix,
		viewportVector);
}

ldraw::id_t PartRenderer::pick(const QPoint& where)
{
	const gl::RenderStyle oldRenderStyle = this->renderPreferences.style;
	this->renderPreferences.style = gl::RenderStyle::PickScene;
	this->makeCurrent();
	this->renderScene();
	std::array<GLubyte, 3> data;
	this->checkForGLErrors();
	glReadPixels(where.x(), this->height() - where.y(), 1, 1, GL_RGB, GL_UNSIGNED_BYTE, &data[0]);
	this->checkForGLErrors();
	this->renderPreferences.style = oldRenderStyle;
	this->update();
	return gl::idFromColor(data);
}

/**
 * @brief Changes the color of rendered fragments
 * @param newFragmentStyle new fragment style to use
 */
void PartRenderer::setFragmentStyle(gl::FragmentStyle newFragmentStyle)
{
	gl::setShaderUniform(&this->shaders, "fragmentStyle", static_cast<int>(newFragmentStyle));
}

/**
 * @brief Changes the way the scene is rendered
 * @param newStyle new render style to use
 */
void PartRenderer::setRenderPreferences(const gl::RenderPreferences& newPreferences)
{
	bool mainColorChanged = this->renderPreferences.mainColor != newPreferences.mainColor;
	bool backgroundColorChanged = this->renderPreferences.backgroundColor != newPreferences.backgroundColor;
	this->renderPreferences = newPreferences;
	if (mainColorChanged or backgroundColorChanged)
	{
		this->build();
	}
	Q_EMIT this->renderPreferencesChanged();
	this->update();
}

/**
 * @return the currently highlighted object
 */
ldraw::id_t PartRenderer::getHighlightedObject() const
{
	return this->highlighted;
}