src/gl/gridprogram.cpp

/*
 *  LDForge: LDraw parts authoring CAD
 *  Copyright (C) 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 "gridprogram.h"

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

layout (location = 0) in vec2 in_position;
uniform mat4 mvp;
smooth out vec2 ex_uv;
uniform mat4 grid;

void main()
{
	gl_Position = mvp * grid * vec4(in_position, 0.0, 1.0);
	ex_uv = in_position;
}
)";

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

out vec4 color;
smooth in vec2 ex_uv;
uniform vec4 gridColor;

void main(void)
{
	float dx = fract(ex_uv.y);
	float dy = fract(ex_uv.x);
	/* fade the grid towards extreme co-ordinates */
	float d = (1.0f - 0.015 * max(abs(ex_uv.x), abs(ex_uv.y)));
	color = vec4(gridColor.xyz, gridColor.w * d);
}
)";

template<int extent>
constexpr auto calcGridData()
{
	std::array<glm::vec2, 8 * extent + 4> result;
	int ix = 0;
	for (int i = -extent; i <= extent; i += 1) {
		result[ix++] = {i, -extent};
		result[ix++] = {i, extent};
	}
	for (int i = -extent; i <= extent; i += 1) {
		result[ix++] = {-extent, i};
		result[ix++] = {extent, i};
	}
	return result;
}

void GridLayer::setGridMatrix(const glm::mat4& newGridMatrix)
{
	this->gridMatrix = newGridMatrix;
	if (this->isInitialized) {
		this->shader.setUniformMatrix("grid", newGridMatrix);
	}
}

void GridLayer::setGridColor(const QColor& newGridColor)
{
	this->gridColor = gl::colorToVector4(newGridColor);
	if (this->isInitialized) {
		this->shader.setUniformVector("gridColor", this->gridColor);
	}
}

void GridLayer::initializeGL()
{
	this->shader.initialize(
		::vertexShaderSource,
		::fragmentShaderSource,
		QOpenGLBuffer::StaticDraw,
		{
			GLAttributeSpec{
				.type = GL_FLOAT,
				.offset = 0,
				.tuplesize = 2,
				.stride = 0,
			},
		}
	);
	this->isInitialized = true;
	constexpr auto data = calcGridData<50>();
	this->shader.setUniformVector("gridColor", this->gridColor);
	this->setGridMatrix(this->gridMatrix);
	this->shader.bufferData(data.data(), data.size(), sizeof data[0]);
}

void GridLayer::paintGL()
{
	glLineWidth(1);
	glEnable(GL_BLEND);
	glLineStipple(1, 0x8888);
	glEnable(GL_LINE_STIPPLE);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	this->shader.draw(GL_LINES);
	glDisable(GL_BLEND);
	glDisable(GL_LINE_STIPPLE);
}

void GridLayer::mvpMatrixChanged(const glm::mat4& mvpMatrix)
{
	this->shader.setMvpMatrix(mvpMatrix);
}