2.2 Uniforms
https://www.khronos.org/opengl/wiki/Uniform_(GLSL)
Complete Source Code:
Graphics.cpp
#include "Graphics.h"
#include <glm/glm.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <iostream>
#include <vector>
#include "Shader.h"
using namespace std;
using namespace glm;
struct Vertex {
vec3 Position;
vec4 Color;
Vertex(const vec3& position, const vec4& color)
: Position(position), Color(color)
{}
};
uvec2 framebuffersize(0, 0);
GLuint program = 0;
GLuint vertexshader = 0;
GLuint fragmentshader = 0;
GLuint vertexarray = 0;
GLuint vertexbuffer = 0;
bool Graphics::Initialize(unsigned int width, unsigned int height)
{
/* set view port */
Resize(width, height);
/* general settings */
glClearColor(0.3f, 0.3f, 0.3f, 0.0f); /* background gray */
/* create all objects */
program = glCreateProgram();
vertexshader = glCreateShader(GL_VERTEX_SHADER);
fragmentshader = glCreateShader(GL_FRAGMENT_SHADER);
glGenVertexArrays(1, &vertexarray);
glGenBuffers(1, &vertexbuffer);
/* shader source */
string vertexshader_source(
"#version 450 core\n"
"in layout (location = 0) vec3 in_position;"
"in layout (location = 1) vec4 in_color;"
"uniform layout (location = 2) vec3 position_offset = vec3(0, 0, 0);"
"smooth out vec4 color;"
"void main() {"
"gl_Position = vec4(position_offset + in_position, 1);"
"color = in_color;"
"}"
);
string fragmentshader_source(
"#version 450 core\n"
"smooth in vec4 color;"
"out layout (location = 0) vec4 out_color;"
"void main() {"
"out_color = color;"
"}"
);
/* compile shaders */
if (!CompileShader(vertexshader, vertexshader_source))
return false;
if (!CompileShader(fragmentshader, fragmentshader_source))
return false;
/* link program */
list<GLuint> shaderlist;
shaderlist.push_back(vertexshader);
shaderlist.push_back(fragmentshader);
if (!LinkProgram(program, shaderlist))
return false;
/* setup vertexarray */
glBindVertexArray(vertexarray);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, Position)));
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, Color)));
glBindBuffer(GL_ARRAY_BUFFER, 0);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glBindVertexArray(0);
/* setup vertexbuffer */
vector<Vertex> vertices;
vertices.push_back(Vertex(vec3(0, 0, 0), vec4(1, 0, 0, 1)));
vertices.push_back(Vertex(vec3(1, 0, 0), vec4(0, 1, 0, 1)));
vertices.push_back(Vertex(vec3(0, 1, 0), vec4(0, 0, 1, 1)));
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * vertices.size(), vertices.data(), GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
/* successfully initialized */
return true;
}
void Graphics::CleanUp()
{
/* destroy all objects */
glDeleteProgram(program);
glDeleteShader(vertexshader);
glDeleteShader(fragmentshader);
glDeleteVertexArrays(1, &vertexarray);
glDeleteBuffers(1, &vertexbuffer);
}
void Graphics::Render()
{
/* set value for "vec4 position_offset" in vertex shader */
GLint location = 2;
static float x = 0.0f; x += 0.05f;
vec3 position_offset = vec3(sin(x), 0, 0);
glProgramUniform3fv(program, location, 1, value_ptr(position_offset));
/* clear framebuffer */
glClear(GL_COLOR_BUFFER_BIT);
/* draw triangle */
glUseProgram(program);
glBindVertexArray(vertexarray);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(0);
glUseProgram(0);
CheckForGLError();
}
void Graphics::Resize(unsigned int width, unsigned int height)
{
framebuffersize = uvec2(width, height);
glViewport(0, 0, width, height);
}
GLContextInfo Graphics::GetContextInfos()
{
GLContextInfo infos;
glGetIntegerv(GL_MAJOR_VERSION, &infos.Version.Major);
glGetIntegerv(GL_MINOR_VERSION, &infos.Version.Minor);
infos.Version.Driver = (const char*)glGetString(GL_VERSION);
infos.Vendor = (const char*)glGetString(GL_VENDOR);
infos.Renderer = (const char*)glGetString(GL_RENDERER);
infos.Version.ShadingLanguage = (const char*)glGetString(GL_SHADING_LANGUAGE_VERSION);
GLint numberofextensions = 0;
glGetIntegerv(GL_NUM_EXTENSIONS, &numberofextensions);
for (int i = 0; i < numberofextensions; i++)
infos.SupportedExtensions.push_back((const char*)glGetStringi(GL_EXTENSIONS, i));
GLint numberofsupportedglslversions = 0;
glGetIntegerv(GL_NUM_SHADING_LANGUAGE_VERSIONS, &numberofsupportedglslversions);
for (int i = 0; i < numberofsupportedglslversions; i++)
infos.SupportedGLSLVersions.push_back((const char*)glGetStringi(GL_SHADING_LANGUAGE_VERSION, i));
return infos;
}
void Graphics::CheckForGLError()
{
for (GLenum error; (error = glGetError()) != GL_NO_ERROR;)
{
cout << "OpenGL Error: \t";
if (error == GL_INVALID_ENUM)
cout << "GL_INVALID_ENUM";
if (error == GL_INVALID_VALUE)
cout << "GL_INVALID_VALUE";
if (error == GL_INVALID_OPERATION)
cout << "GL_INVALID_OPERATION";
if (error == GL_STACK_OVERFLOW)
cout << "GL_STACK_OVERFLOW";
if (error == GL_STACK_UNDERFLOW)
cout << "GL_STACK_UNDERFLOW";
if (error == GL_OUT_OF_MEMORY)
cout << "GL_OUT_OF_MEMORY";
if (error == GL_INVALID_FRAMEBUFFER_OPERATION)
cout << "GL_INVALID_FRAMEBUFFER_OPERATION";
if (error == GL_CONTEXT_LOST)
cout << "GL_CONTEXT_LOST";
cout << (char)7 << endl; /*play sound*/
cin.get();
}
}