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/* OpenGL example code - Instancing with texture buffer
*
* create 8 instances of the cube from the perspective example
* the difference to the instancing1 example is that we are
* using a texture buffer for the per instance data instead of a
* vertex buffer with divisor.
*
* Autor: Jakob Progsch
*/
#include <GLXW/glxw.h>
#include <GLFW/glfw3.h>
//glm is used to create perspective and transform matrices
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <iostream>
#include <string>
#include <vector>
// helper to check and display for shader compiler errors
bool check_shader_compile_status(GLuint obj) {
GLint status;
glGetShaderiv(obj, GL_COMPILE_STATUS, &status);
if(status == GL_FALSE) {
GLint length;
glGetShaderiv(obj, GL_INFO_LOG_LENGTH, &length);
std::vector<char> log(length);
glGetShaderInfoLog(obj, length, &length, &log[0]);
std::cerr << &log[0];
return false;
}
return true;
}
// helper to check and display for shader linker error
bool check_program_link_status(GLuint obj) {
GLint status;
glGetProgramiv(obj, GL_LINK_STATUS, &status);
if(status == GL_FALSE) {
GLint length;
glGetProgramiv(obj, GL_INFO_LOG_LENGTH, &length);
std::vector<char> log(length);
glGetProgramInfoLog(obj, length, &length, &log[0]);
std::cerr << &log[0];
return false;
}
return true;
}
int main() {
int width = 640;
int height = 480;
if(glfwInit() == GL_FALSE) {
std::cerr << "failed to init GLFW" << std::endl;
return 1;
}
// select opengl version
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
// create a window
GLFWwindow *window;
if((window = glfwCreateWindow(width, height, "06instancing2_buffer_texture", 0, 0)) == 0) {
std::cerr << "failed to open window" << std::endl;
glfwTerminate();
return 1;
}
glfwMakeContextCurrent(window);
if(glxwInit()) {
std::cerr << "failed to init GL3W" << std::endl;
glfwDestroyWindow(window);
glfwTerminate();
return 1;
}
// shader source code
std::string vertex_source =
"#version 330\n"
"uniform mat4 ViewProjection;\n" // the projection matrix uniform
"uniform samplerBuffer offset_texture;\n" // the buffer_texture sampler
"layout(location = 0) in vec4 vposition;\n"
"layout(location = 1) in vec4 vcolor;\n"
"out vec4 fcolor;\n"
"void main() {\n"
// access the buffer texture with the InstanceID (tbo[InstanceID])
" vec4 offset = texelFetch(offset_texture, gl_InstanceID);\n"
" fcolor = vcolor;\n"
" gl_Position = ViewProjection*(vposition + offset);\n"
"}\n";
std::string fragment_source =
"#version 330\n"
"in vec4 fcolor;\n"
"layout(location = 0) out vec4 FragColor;\n"
"void main() {\n"
" FragColor = fcolor;\n"
"}\n";
// program and shader handles
GLuint shader_program, vertex_shader, fragment_shader;
// we need these to properly pass the strings
const char *source;
int length;
// create and compiler vertex shader
vertex_shader = glCreateShader(GL_VERTEX_SHADER);
source = vertex_source.c_str();
length = vertex_source.size();
glShaderSource(vertex_shader, 1, &source, &length);
glCompileShader(vertex_shader);
if(!check_shader_compile_status(vertex_shader)) {
glfwDestroyWindow(window);
glfwTerminate();
return 1;
}
// create and compiler fragment 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);
if(!check_shader_compile_status(fragment_shader)) {
glfwDestroyWindow(window);
glfwTerminate();
return 1;
}
// create program
shader_program = glCreateProgram();
// attach shaders
glAttachShader(shader_program, vertex_shader);
glAttachShader(shader_program, fragment_shader);
// link the program and check for errors
glLinkProgram(shader_program);
check_program_link_status(shader_program);
// obtain location of projection uniform
GLint ViewProjection_location = glGetUniformLocation(shader_program, "ViewProjection");
GLint offset_texture_location = glGetUniformLocation(shader_program, "offset_texture");
// vao and vbo handles
GLuint vao, vbo, tbo, ibo;
// generate and bind the vao
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// generate and bind the vertex buffer object
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
// data for a cube
GLfloat vertexData[] = {
// X Y Z R G B
// face 0:
1.0f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f, // vertex 0
-1.0f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f, // vertex 1
1.0f,-1.0f, 1.0f, 1.0f, 0.0f, 0.0f, // vertex 2
-1.0f,-1.0f, 1.0f, 1.0f, 0.0f, 0.0f, // vertex 3
// face 1:
1.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.0f, // vertex 0
1.0f,-1.0f, 1.0f, 0.0f, 1.0f, 0.0f, // vertex 1
1.0f, 1.0f,-1.0f, 0.0f, 1.0f, 0.0f, // vertex 2
1.0f,-1.0f,-1.0f, 0.0f, 1.0f, 0.0f, // vertex 3
// face 2:
1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, // vertex 0
1.0f, 1.0f,-1.0f, 0.0f, 0.0f, 1.0f, // vertex 1
-1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, // vertex 2
-1.0f, 1.0f,-1.0f, 0.0f, 0.0f, 1.0f, // vertex 3
// face 3:
1.0f, 1.0f,-1.0f, 1.0f, 1.0f, 0.0f, // vertex 0
1.0f,-1.0f,-1.0f, 1.0f, 1.0f, 0.0f, // vertex 1
-1.0f, 1.0f,-1.0f, 1.0f, 1.0f, 0.0f, // vertex 2
-1.0f,-1.0f,-1.0f, 1.0f, 1.0f, 0.0f, // vertex 3
// face 4:
-1.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, // vertex 0
-1.0f, 1.0f,-1.0f, 0.0f, 1.0f, 1.0f, // vertex 1
-1.0f,-1.0f, 1.0f, 0.0f, 1.0f, 1.0f, // vertex 2
-1.0f,-1.0f,-1.0f, 0.0f, 1.0f, 1.0f, // vertex 3
// face 5:
1.0f,-1.0f, 1.0f, 1.0f, 0.0f, 1.0f, // vertex 0
-1.0f,-1.0f, 1.0f, 1.0f, 0.0f, 1.0f, // vertex 1
1.0f,-1.0f,-1.0f, 1.0f, 0.0f, 1.0f, // vertex 2
-1.0f,-1.0f,-1.0f, 1.0f, 0.0f, 1.0f, // vertex 3
}; // 6 faces with 4 vertices with 6 components (floats)
// fill with data
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat)*6*4*6, vertexData, GL_STATIC_DRAW);
// set up generic attrib pointers
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6*sizeof(GLfloat), (char*)0 + 0*sizeof(GLfloat));
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6*sizeof(GLfloat), (char*)0 + 3*sizeof(GLfloat));
// generate and bind the index buffer object
glGenBuffers(1, &ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
GLuint indexData[] = {
// face 0:
0,1,2, // first triangle
2,1,3, // second triangle
// face 1:
4,5,6, // first triangle
6,5,7, // second triangle
// face 2:
8,9,10, // first triangle
10,9,11, // second triangle
// face 3:
12,13,14, // first triangle
14,13,15, // second triangle
// face 4:
16,17,18, // first triangle
18,17,19, // second triangle
// face 5:
20,21,22, // first triangle
22,21,23, // second triangle
};
// fill with data
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint)*6*2*3, indexData, GL_STATIC_DRAW);
// generate and bind the buffer object containing the
// instance offsets
glGenBuffers(1, &tbo);
glBindBuffer(GL_TEXTURE_BUFFER, tbo);
// the offsets
GLfloat translationData[] = {
2.0f, 2.0f, 2.0f, 0.0f, // cube 0
2.0f, 2.0f,-2.0f, 0.0f, // cube 1
2.0f,-2.0f, 2.0f, 0.0f, // cube 2
2.0f,-2.0f,-2.0f, 0.0f, // cube 3
-2.0f, 2.0f, 2.0f, 0.0f, // cube 4
-2.0f, 2.0f,-2.0f, 0.0f, // cube 5
-2.0f,-2.0f, 2.0f, 0.0f, // cube 6
-2.0f,-2.0f,-2.0f, 0.0f, // cube 7
}; // 8 offsets with 3 components each
// fill with data
glBufferData(GL_TEXTURE_BUFFER, sizeof(GLfloat)*4*8, translationData, GL_STATIC_DRAW);
// texture handle
GLuint buffer_texture;
// generate and bind the buffer texture
glGenTextures(1, &buffer_texture);
glBindTexture(GL_TEXTURE_BUFFER, buffer_texture);
// tell the buffer texture to use
glTexBuffer(GL_TEXTURE_BUFFER, GL_RGBA32F, tbo);
// we are drawing 3d objects so we want depth testing
glEnable(GL_DEPTH_TEST);
while(!glfwWindowShouldClose(window)) {
glfwPollEvents();
// get the time in seconds
float t = glfwGetTime();
// clear first
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// use the shader program
glUseProgram(shader_program);
// calculate ViewProjection matrix
glm::mat4 Projection = glm::perspective(90.0f, 4.0f / 3.0f, 0.1f, 100.f);
// translate the world/view position
glm::mat4 View = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, 0.0f, -5.0f));
// make the camera rotate around the origin
View = glm::rotate(View, 90.0f*t, glm::vec3(1.0f, 1.0f, 1.0f));
glm::mat4 ViewProjection = Projection*View;
// bind texture to texture unit 0
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_BUFFER, buffer_texture);
// set the matrix uniform
glUniformMatrix4fv(ViewProjection_location, 1, GL_FALSE, glm::value_ptr(ViewProjection));
// set texture uniform
glUniform1i(offset_texture_location, 0);
// bind the vao
glBindVertexArray(vao);
// draw
// the additional parameter indicates how many instances to render
glDrawElementsInstanced(GL_TRIANGLES, 6*6, GL_UNSIGNED_INT, 0, 8);
// check for errors
GLenum error = glGetError();
if(error != GL_NO_ERROR) {
std::cerr << error << std::endl;
break;
}
// finally swap buffers
glfwSwapBuffers(window);
}
// delete the created objects
glDeleteVertexArrays(1, &vao);
glDeleteBuffers(1, &vbo);
glDeleteBuffers(1, &ibo);
glDeleteBuffers(1, &tbo);
glDeleteTextures(1, &buffer_texture);
glDetachShader(shader_program, vertex_shader);
glDetachShader(shader_program, fragment_shader);
glDeleteShader(vertex_shader);
glDeleteShader(fragment_shader);
glDeleteProgram(shader_program);
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}
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