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/* LineShader.cpp
Copyright (c) 2014 by Michael Zahniser
Endless Sky 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.
Endless Sky 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 <https://www.gnu.org/licenses/>.
*/
#include "LineShader.h"
#include "../Color.h"
#include "../GameData.h"
#include "../Point.h"
#include "../Screen.h"
#include "Shader.h"
#include <stdexcept>
using namespace std;
namespace {
const Shader *shader;
GLint scaleI;
GLint startI;
GLint endI;
GLint widthI;
GLint fromColorI;
GLint toColorI;
GLint capI;
GLuint vao;
GLuint vbo;
}
void LineShader::Init()
{
shader = GameData::Shaders().Get("line");
if(!shader->Object())
throw std::runtime_error("Could not find line shader!");
scaleI = shader->Uniform("scale");
startI = shader->Uniform("start");
endI = shader->Uniform("end");
widthI = shader->Uniform("width");
fromColorI = shader->Uniform("startColor");
toColorI = shader->Uniform("endColor");
capI = shader->Uniform("cap");
// Generate the vertex data for drawing sprites.
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
GLfloat vertexData[] = {
-1.f, -1.f,
1.f, -1.f,
-1.f, 1.f,
1.f, 1.f
};
glBufferData(GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW);
glEnableVertexAttribArray(shader->Attrib("vert"));
glVertexAttribPointer(shader->Attrib("vert"), 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), nullptr);
// unbind the VBO and VAO
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}
void LineShader::Draw(const Point &from, const Point &to, float width, const Color &color, bool roundCap)
{
DrawGradient(from, to, width, color, color, roundCap);
}
void LineShader::DrawDashed(const Point &from, const Point &to, const Point &unit, const float width,
const Color &color, const double dashLength, double spaceLength, bool roundCap)
{
const double length = (to - from).Length();
const double patternLength = dashLength + spaceLength;
int segments = length / patternLength;
// If needed, scale pattern down so we can draw at least two of them over length.
if(segments < 2)
{
segments = 2;
spaceLength *= length / (segments * patternLength);
}
spaceLength /= 2.;
float capOffset = roundCap ? width : 0.;
for(int i = 0; i < segments; ++i)
Draw(from + unit * (i * length / segments + spaceLength + capOffset),
from + unit * ((i + 1) * length / segments - spaceLength - capOffset),
width, color, roundCap);
}
void LineShader::DrawGradient(const Point &from, const Point &to, float width,
const Color &fromColor, const Color &toColor, bool roundCap)
{
if(!shader->Object())
throw runtime_error("LineShader: Draw() called before Init().");
glUseProgram(shader->Object());
glBindVertexArray(vao);
GLfloat scale[2] = {static_cast<GLfloat>(Screen::Width()), static_cast<GLfloat>(Screen::Height())};
glUniform2fv(scaleI, 1, scale);
GLfloat start[2] = {static_cast<float>(from.X()), static_cast<float>(from.Y())};
glUniform2fv(startI, 1, start);
GLfloat end[2] = {static_cast<float>(to.X()), static_cast<float>(to.Y())};
glUniform2fv(endI, 1, end);
glUniform1f(widthI, width);
glUniform4fv(fromColorI, 1, fromColor.Get());
glUniform4fv(toColorI, 1, toColor.Get());
glUniform1i(capI, static_cast<GLint>(roundCap));
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glBindVertexArray(0);
glUseProgram(0);
}
void LineShader::DrawGradientDashed(const Point &from, const Point &to, const Point &unit, const float width,
const Color &fromColor, const Color &toColor, const double dashLength, double spaceLength, bool roundCap)
{
const double length = (to - from).Length();
const double patternLength = dashLength + spaceLength;
int segments = length / patternLength;
// If needed, scale pattern down so we can draw at least two of them over length.
if(segments < 2)
{
segments = 2;
spaceLength *= length / (segments * patternLength);
}
spaceLength /= 2.;
float capOffset = roundCap ? width : 0.;
for(int i = 0; i < segments; ++i)
{
float p = static_cast<float>(i) / segments;
Color mixed = Color::Combine(1. - p, fromColor, p, toColor);
float pv = static_cast<float>(i + 1) / segments;
Color mixed2 = Color::Combine(1. - pv, fromColor, pv, toColor);
DrawGradient(from + unit * (i * length / segments + spaceLength + capOffset),
from + unit * ((i + 1) * length / segments - spaceLength - capOffset),
width, mixed, mixed2, roundCap);
}
}
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