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 <GL/glut.h>
#include <glm/ext/matrix_transform.hpp>
#include <glm/ext/matrix_clip_space.hpp>
#include <QMouseEvent>
#include <QMessageBox>
#include "partrenderer.h"

PartRenderer::PartRenderer(
	Model* model,
	DocumentManager* documents,
	const ldraw::ColorTable& colorTable,
	QWidget* parent) :
	QOpenGLWidget{parent},
	model{model},
	documents{documents},
	colorTable{colorTable},
	compiler{new gl::Compiler{this->colorTable, this}}
{
	this->setMouseTracking(true);
}

PartRenderer::~PartRenderer()
{
}

void PartRenderer::initializeGL()
{
	this->initializeOpenGLFunctions();
	if (glGetError() != GL_NO_ERROR)
	{
		abort();
	}
	this->compiler->initialize();
	this->compiler->build(this->model, this->documents);
	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->updateViewMatrix();
	glLineWidth(2.0);
	this->update();
}

void PartRenderer::resizeGL(int width, int 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);
	this->compiler->setUniformMatrix("projectionMatrix", this->projectionMatrix);
}

static 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 vbo class passed to getGlTypeForVboClass"};
}

void PartRenderer::paintGL()
{
	/*
	glEnable (GL_BLEND);
	glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	*/
	glEnable (GL_DEPTH_TEST);
	glShadeModel (GL_SMOOTH);
	glEnable (GL_MULTISAMPLE);
	glEnable (GL_LINE_SMOOTH);
	glHint (GL_LINE_SMOOTH_HINT, GL_NICEST);
	this->renderScene();
}

void PartRenderer::renderScene()
{
	glClearColor(0.8f, 0.8f, 0.8f, 1.0f);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_POLYGON_OFFSET_FILL);
	glPolygonOffset(1.0f, 1.0f);
	switch (this->renderStyle)
	{
	case gl::RenderStyle::Normal:
		this->setFragmentStyle(gl::FragmentStyle::Normal);
		this->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);
	case gl::RenderStyle::RandomColors:
		this->setFragmentStyle(gl::FragmentStyle::RandomColors);
		this->renderAllArrays();
		break;
	case gl::RenderStyle::Wireframe:
		glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
		this->setFragmentStyle(gl::FragmentStyle::Normal);
		this->renderAllArrays();
		break;
	}
	glDisable(GL_POLYGON_OFFSET_FILL);
}

void PartRenderer::renderAllArrays()
{
	// Lines need to be rendered last so that anti-aliasing does not interfere with polygon rendering.
	renderVao(gl::ArrayClass::Triangles);
	renderVao(gl::ArrayClass::Quads);
	renderVao(gl::ArrayClass::Lines);
}


void PartRenderer::updateViewMatrix()
{
	// I'm not quite sure why using the exponent function on the zoom factor causes linear zoom behavior
	const double z  = 2 * std::exp(this->zoom) * (1 + this->compiler->modelDistance());
	this->viewMatrix = glm::lookAt(glm::vec3{0, 0, z}, {0, 0, 0}, {0, -1, 0});
	this->compiler->setUniformMatrix("viewMatrix", this->viewMatrix);
}

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

void PartRenderer::checkForGLErrors()
{
	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::critical(
			this,
			tr("Rendering error"),
			QString{"Failed to render.\n%1"}.arg(errors.join("\n")));
	}
}

void PartRenderer::mouseMoveEvent(QMouseEvent* event)
{
	const bool left = event->buttons() & Qt::LeftButton;
	const QPointF move = pointToPointF(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->compiler->setUniformMatrix("modelMatrix", glm::mat4_cast(this->modelQuaternion));
		this->update();
	}
	this->lastMousePosition = pointToPointF(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 Changes the color of rendered fragments
 * @param newFragmentStyle new fragment style to use
 */
void PartRenderer::setFragmentStyle(gl::FragmentStyle newFragmentStyle)
{
	this->compiler->setUniform("fragmentStyle", static_cast<int>(newFragmentStyle));
}

/**
 * @brief Changes the way the scene is rendered
 * @param newStyle new render style to use
 */
void PartRenderer::setRenderStyle(const gl::RenderStyle newStyle)
{
	this->renderStyle = newStyle;
	this->update();
}