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#define GL_GLEXT_PROTOTYPES
#define EGL_EGLEXT_PROTOTYPES
#include <cmath>
#include <iostream>
#include <vector>
extern "C" {
#include <GL/gl.h>
#include <GL/glut.h>
}
static const char vertex_shader[] =
"#ifdef GL_ES\n"
"precision lowp float;\n"
"#endif\n"
"attribute float indices;\n"
"uniform sampler2D nodeInfo;\n"
"varying vec4 color;"
"\n"
"void main(void)\n"
"{\n"
" float s = (indices + 0.5) / 512.; \n"
" vec4 v = texture2D(nodeInfo, vec2( s, 0.5));\n"
" gl_Position = vec4(v.x, v.y, 0.5, 1.);\n"
" gl_PointSize = v.z;\n"
" color = vec4(0.5 + v.w/2., 0.5 + 0.5 * v.w/2., 0.5, 1);\n"
"}\n";
static const char fragment_shader[] =
"#ifdef GL_ES\n"
"precision lowp float;\n"
"#endif\n"
"\n"
"varying vec4 color;\n"
"void main(void)\n"
"{\n"
" float dst = distance(vec2(0.5, 0.5), gl_PointCoord); \n"
" gl_FragColor = color;\n"
" if ( dst > 0.3) {"
" gl_FragColor = vec4(0., 0., 0.5, 0.2);\n"
"}\n"
"if ( dst > 0.5) discard;\n"
"}";
struct NodeInfo { //structure that we want to transmit to our shaders
float x;
float y;
float s;
float c;
};
GLuint nodeTexture; //texture id used to bind
GLuint nodeSamplerLocation; //shader sampler address
GLuint indicesAttributeLocation; //shader attribute address
GLuint indicesVBO; //Vertex Buffer Object Id;
const int nbNodes = 512;
NodeInfo data[nbNodes]; //our data that will be transmitted using float texture.
double alpha = 0; //use to make a simple funny effect;
static void updateFloatTexture() {
int count = 0;
for (float x=0; x < nbNodes; ++x ) {
data[count].x = 0.2*pow(cos(alpha), 3) + (sin(alpha)*3. + 3.5) * x/nbNodes * cos(alpha + x/nbNodes * 16. * M_PI);
data[count].y = 0.2*pow(sin(alpha), 3) + (sin(alpha)*3. + 3.5) * x/nbNodes * sin(alpha + x/nbNodes * 16. * M_PI);
data[count].s = (16. + 16. * cos(alpha + x/nbNodes * 32. * M_PI)) + 8.;// * fmod(x/nbNodes + alpha, 1.) + 5.;
data[count].c = 0.5 + 0.5 * sin(alpha + x/nbNodes * 32. * M_PI);
++count;
}
glBindTexture(GL_TEXTURE_2D, nodeTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, nbNodes, 1, 0, GL_RGBA, GL_FLOAT, data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glBindTexture(GL_TEXTURE_2D, NULL);
alpha -= 0.001;
}
static void glut_draw_callback(void) {
glDisable(GL_CULL_FACE);
glDisable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glClearColor(1., 1., 1., 0.);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glActiveTexture(GL_TEXTURE0);
updateFloatTexture(); //we change the texture each time to create the effect (it is just for the test)
glBindTexture(GL_TEXTURE_2D, nodeTexture);
glUniform1i(nodeSamplerLocation, GL_TEXTURE0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, indicesVBO);
glVertexAttribPointer(0, 1, GL_FLOAT, GL_FALSE, 0, NULL);
glDrawArrays(GL_POINTS, 0, nbNodes);
glutSwapBuffers();
}
GLuint createShader(const char source[], int type) {
char msg[512];
GLuint shader = glCreateShader(type);
glShaderSource(shader, 1, (const GLchar**)(&source), NULL);
glCompileShader(shader);
glGetShaderInfoLog(shader, sizeof msg, NULL, msg);
std::cout << "Shader info: " << msg << std::endl;
return shader;
}
static void gl_init(void) {
GLuint program = glCreateProgram();
glAttachShader(program, createShader(vertex_shader , GL_VERTEX_SHADER));
glAttachShader(program, createShader(fragment_shader, GL_FRAGMENT_SHADER));
glLinkProgram(program);
char msg[512];
glGetProgramInfoLog(program, sizeof msg, NULL, msg);
std::cout << "info: " << msg << std::endl;
glUseProgram(program);
std::vector<float> elements(nbNodes);
int count = 0;
for (float x=0; x < nbNodes; ++x ) {
elements[count] = count;
++count;
}
/*Create one texture to store all the needed information */
glGenTextures(1, &nodeTexture);
/* Store the vertices in a vertex buffer object (VBO) */
glGenBuffers(1, &indicesVBO);
glBindBuffer(GL_ARRAY_BUFFER, indicesVBO);
float zeroes[nbNodes];
memset(zeroes, 0, sizeof(zeroes));
glBufferData(GL_ARRAY_BUFFER, elements.size() * sizeof(float), zeroes, GL_STATIC_DRAW);
for (int x = 0; x < nbNodes; x++) {
glBufferSubData(GL_ARRAY_BUFFER, x * sizeof(float), elements.size() * sizeof(float), &elements[x]);
}
/* Get the locations of the uniforms so we can access them */
nodeSamplerLocation = glGetUniformLocation(program, "nodeInfo");
glBindAttribLocation(program, 0, "indices");
//Enable glPoint size in shader, always enable in Open Gl ES 2.
glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
glEnable(GL_POINT_SPRITE);
}
int main(int argc, char *argv[]) {
glutInit(&argc, argv);
glutInitWindowSize(640, 480);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutCreateWindow("Simple FLOAT Texture Test");
/* Set up glut callback functions */
glutDisplayFunc(glut_draw_callback );
gl_init();
glutMainLoop();
return 0;
}
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