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#include <GL/glew.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <SDL2/SDL.h>
#include <stdio.h>
bool loadFromMemory (const char* vertexShaderCode, const char* fragmentShaderCode, unsigned int& shaderProgram) {
//Program.
shaderProgram = glCreateProgram();
//Vertex shader.
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource (vertexShader, 1, &vertexShaderCode, NULL);
glCompileShaderARB(vertexShader);
GLint success;
glGetObjectParameterivARB(vertexShader, GL_OBJECT_COMPILE_STATUS_ARB, &success);
if (success == GL_FALSE)
{
char log[1024];
glGetInfoLogARB(vertexShader, sizeof(log), 0, log);
printf("Failed to compile vertex shader code : %s\n", log);
glDeleteShader(vertexShader);
glDeleteProgram(shaderProgram);
shaderProgram = 0;
return false;
}
glAttachShader(shaderProgram, vertexShader);
glDeleteShader(vertexShader);
//Fragment shader.
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSourceARB(fragmentShader, 1, &fragmentShaderCode, NULL);
glCompileShaderARB(fragmentShader);
glGetObjectParameterivARB(fragmentShader, GL_OBJECT_COMPILE_STATUS_ARB, &success);
if (success == GL_FALSE)
{
char log[1024];
glGetInfoLogARB(fragmentShader, sizeof(log), 0, log);
printf("Failed to compile fragment shader code : %s\n", log);
glDeleteShader(fragmentShader);
glDeleteShader(shaderProgram);
shaderProgram = 0;
return false;
}
glAttachShader(shaderProgram, fragmentShader);
glDeleteShader(fragmentShader);
//Linkage.
glLinkProgram(shaderProgram);
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (success == GL_FALSE)
{
char log[1024];
glGetInfoLogARB(fragmentShader, sizeof(log), 0, log);
printf("Failed to link shader program : %s\n", log);
glDeleteShader(shaderProgram);
shaderProgram = 0;
return false;
}
glFlush();
return true;
}
void setParameter (unsigned int shaderProgram, const char* name, float x, float y) {
glUseProgram(shaderProgram);
GLint location = glGetUniformLocation(shaderProgram, name);
glUniform2f(location, x, y);
}
bool createTexture (unsigned int width, unsigned int height, const char* pixels, unsigned int& texture) {
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
if (texture)
return true;
return false;
}
int main(int argc, char** argv) {
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
fprintf(stdout,"Échec de l'initialisation de la SDL (%s)\n",SDL_GetError());
return -1;
}
SDL_Init(SDL_INIT_VIDEO);
SDL_Window* window = SDL_CreateWindow("test SDL2/Opengl", 0, 0, 800, 600,
SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
SDL_GLContext glcontext = SDL_GL_CreateContext(window);
GLenum err = glewInit();
if (err == GL_TRUE) {
printf("Failed to initialize glew!");
}
bool terminated = false;
glMatrixMode(GL_PROJECTION);
gluPerspective(80, 800/600, 1, 1000);
glMatrixMode(GL_MODELVIEW);
gluLookAt(0, 0, 0, 0, 1, 0, 0, 0, 1);
int texSize = 5;
glPointSize(texSize);
const char* vertexShaderCode =
"#version 130 \n"
"void main() {"
" gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;"
" gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;"
" gl_FrontColor = gl_Color;"
"}";
const char* fragmentShaderCode =
"#version 130 \n"
"const ivec2 resolution = ivec2 (800, 600);"
"uniform sampler2D tex;"
"void main() {"
" vec4 texel = texture(tex, gl_TexCoord[0].xy);"
" gl_FragColor = gl_Color * texel;"
"}";
GLuint shaderProgram = 0;
if(!loadFromMemory(vertexShaderCode, fragmentShaderCode, shaderProgram)) {
printf("failed to load shader program!");
exit(-1);
}
char pixels[800*600*4];
float halfTexSize = texSize * 0.5f;
for (unsigned int j = 0; j < 600; j++) {
for (unsigned int i = 0; i < 800; i++) {
if (i < texSize && j < texSize) {
pixels[(j*800+i)*4] = 255;
pixels[(j*800+i)*4+1] = 255;
pixels[(j*800+i)*4+2] = 0;
float attenuation = sqrt((i-halfTexSize)*(i-halfTexSize)+(j-halfTexSize)*(j-halfTexSize)) / texSize;
pixels[(j*800+i)*4+2] = 255 * attenuation;
} else {
pixels[(j*800+i)*4] = 0;
pixels[(j*800+i)*4+1] = 0;
pixels[(j*800+i)*4+2] = 0;
pixels[(j*800+i)*4+3] = 0;
}
}
}
unsigned int texture;
createTexture(800, 600, pixels, texture);
glEnable (GL_BLEND);
glBlendFunc (GL_SRC_ALPHA, GL_ONE);
glUseProgram(shaderProgram);
while (!terminated) {
glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_POINTS);
glColor3f(1, 1, 0);
for (int x = -10; x <= 10; ++x) {
for (int y = -10; y <= 10; ++y) {
glTexCoord2f(0, 0);
glVertex3i(x, y, 1);
}
}
glEnd();
SDL_GL_SwapWindow(window);
SDL_Event event;
while (SDL_PollEvent(&event)) {
if (event.window.event == SDL_WINDOWEVENT_CLOSE)
terminated = true;
}
}
SDL_GL_DeleteContext(glcontext);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
} |
