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4_shader_uniform.h
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4_shader_uniform.h
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#pragma once
#include "../common.h"
// use uniform to change color per loop
static int tutorial4(){
// config opengl
GLFWwindow* window = nullptr;
if (commonInit(&window) < 0) {
return -1;
}
const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n{"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n{"
" FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\0";
const char* fragmentShaderSource2 = "#version 330 core\n"
"out vec4 FragColor;\n"
"uniform vec4 u_color;\n"
"void main()\n{"
" FragColor = u_color;\n"
"}\0";
// create two shader program
unsigned int shaderProgram = createShaderProgram(vertexShaderSource, fragmentShaderSource);
unsigned int shaderProgram2 = createShaderProgram(vertexShaderSource, fragmentShaderSource2);
// vertex data
float firstTriangleVer[] = {
-1.0f, -0.5f, 0.0f, // left
0.0f, -0.5f, 0.0f, // right
-0.5f, 0.5f, 0.0f // top
};
float secondTriangleVer[] = {
0.0f, -0.5f, 0.0f,
1.0f, -0.5f, 0.0f,
0.5f, 0.5f, 0.0f
};
// gen
unsigned int VBOs[2], VAOs[2];
glGenVertexArrays(2, VAOs);
glGenBuffers(2, VBOs);
// bind first triangle info
glBindVertexArray(VAOs[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(firstTriangleVer), firstTriangleVer, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// bind second triangle info
glBindVertexArray(VAOs[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(secondTriangleVer), secondTriangleVer, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// render loop
while (!glfwWindowShouldClose(window)) {
// handle input event
processInput(window);
// render
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// draw triangle
glUseProgram(shaderProgram);
glBindVertexArray(VAOs[0]);
glDrawArrays(GL_TRIANGLES, 0, 3);
// draw second triangle
float timeValue = glfwGetTime();
float greenValue = sin(timeValue) / 2.0f + 0.5f;
int uniformLocation = glGetUniformLocation(shaderProgram2, "u_color");
if (uniformLocation != -1){
glUseProgram(shaderProgram2);
glUniform4f(uniformLocation, 0.0f, greenValue, 0.0f, 1.0f);
glBindVertexArray(VAOs[1]);
glDrawArrays(GL_TRIANGLES, 0, 3);
}
glfwSwapBuffers(window);
glfwPollEvents();
}
glDeleteVertexArrays(2, VAOs);
glDeleteBuffers(2, VBOs);
glfwTerminate();
return 0;
}