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March 6, 2022 17:16
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// to keep my sanity heres a simplified version of a texture demo for my future self | |
// original from: github.com/progschj/OpenGL-Examples/blob/master/03texture.cpp | |
#define GL_GLEXT_PROTOTYPES | |
#include <GLFW/glfw3.h> | |
#include <iostream> | |
#include <string> | |
#include <vector> | |
int screenwidth = 640; | |
int screenheight = 480; | |
int texwidth = screenwidth * 0.15; | |
int texheight = screenheight * 0.15; | |
GLuint shader_program, vertex_shader, fragment_shader; | |
GLuint texture; | |
std::string vertex_source = | |
"#version 330\n" | |
"layout(location = 0) in vec4 vposition;\n" | |
"layout(location = 1) in vec2 vtexcoord;\n" | |
"out vec2 ftexcoord;\n" | |
"void main() {\n" | |
" ftexcoord = vtexcoord;\n" | |
" gl_Position = vposition;\n" | |
"}\n"; | |
std::string fragment_source = | |
"#version 330\n" | |
"uniform sampler2D tex;\n" | |
"in vec2 ftexcoord;\n" | |
"layout(location = 0) out vec4 FragColor;\n" | |
"void main() {\n" | |
" FragColor = texture(tex, ftexcoord);\n" | |
"}\n"; | |
GLfloat vertexData[] = { | |
1.0f, 1.0f, 0.0f, 1.0f, 1.0f, | |
-1.0f, 1.0f, 0.0f, 0.0f, 1.0f, | |
1.0f,-1.0f, 0.0f, 1.0f, 0.0f, | |
-1.0f,-1.0f, 0.0f, 0.0f, 0.0f, | |
}; | |
GLuint indexData[] = { | |
0,1,2, | |
2,1,3, | |
}; | |
int main(){ | |
glfwInit(); | |
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); | |
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); | |
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); | |
GLFWwindow *window = glfwCreateWindow(screenwidth, screenheight, "Textures with OpenGL", 0, 0); | |
glfwMakeContextCurrent(window); | |
const char *source; | |
int length; | |
vertex_shader = glCreateShader(GL_VERTEX_SHADER); | |
source = vertex_source.c_str(); | |
length = vertex_source.size(); | |
glShaderSource(vertex_shader, 1, &source, &length); | |
glCompileShader(vertex_shader); | |
fragment_shader = glCreateShader(GL_FRAGMENT_SHADER); | |
source = fragment_source.c_str(); | |
length = fragment_source.size(); | |
glShaderSource(fragment_shader, 1, &source, &length); | |
glCompileShader(fragment_shader); | |
shader_program = glCreateProgram(); | |
glAttachShader(shader_program, vertex_shader); | |
glAttachShader(shader_program, fragment_shader); | |
glLinkProgram(shader_program); | |
GLint texture_location = glGetUniformLocation(shader_program, "tex"); | |
GLuint vao, vbo, ibo; | |
// vao and vbo | |
glGenVertexArrays(1, &vao); | |
glBindVertexArray(vao); | |
glGenBuffers(1, &vbo); | |
glBindBuffer(GL_ARRAY_BUFFER, vbo); | |
glBufferData(GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW); | |
glEnableVertexAttribArray(0); | |
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), (char*)0 + 0*sizeof(GLfloat)); | |
glEnableVertexAttribArray(1); | |
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), (char*)0 + 3*sizeof(GLfloat)); | |
// ibo | |
glGenBuffers(1, &ibo); | |
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo); | |
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indexData), indexData, GL_STATIC_DRAW); | |
glBindVertexArray(0); | |
// texture | |
glGenTextures(1, &texture); | |
glBindTexture(GL_TEXTURE_2D, texture); | |
std::vector<GLubyte> image(4*texwidth*texheight); | |
for(int j = 0;j<texheight;++j) { | |
for(int i = 0;i<texwidth;++i) { | |
size_t index = j*texwidth + i; | |
image[4*index + 0] = 0xFF*(rand()/(float)RAND_MAX); | |
image[4*index + 1] = 0xFF*(rand()/(float)RAND_MAX); | |
image[4*index + 2] = 0xFF*(rand()/(float)RAND_MAX); | |
image[4*index + 3] = 0xFF; | |
} | |
} | |
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); | |
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); | |
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); | |
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); | |
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, texwidth, texheight, 0, GL_RGBA, GL_UNSIGNED_BYTE, &image[0]); | |
while(!glfwWindowShouldClose(window)) { | |
glfwPollEvents(); | |
glClear(GL_COLOR_BUFFER_BIT); | |
glUseProgram(shader_program); | |
glActiveTexture(GL_TEXTURE0); | |
glBindTexture(GL_TEXTURE_2D, texture); | |
glUniform1i(texture_location, 0); | |
glBindVertexArray(vao); | |
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0); | |
glfwSwapBuffers(window); | |
} | |
glfwTerminate(); | |
return 0; | |
} | |
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