ref: 9c1d7cd3f819fcc3cb0a634ef5ca2ff3777c9cca
dir: /external/glfw/examples/heightmap.c/
//========================================================================
// Heightmap example program using OpenGL 3 core profile
// Copyright (c) 2010 Olivier Delannoy
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software. If you use this software
// in a product, an acknowledgment in the product documentation would
// be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
// be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
// distribution.
//
//========================================================================
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <stddef.h>
#include <glad/gl.h>
#define GLFW_INCLUDE_NONE
#include <GLFW/glfw3.h>
/* Map height updates */
#define MAX_CIRCLE_SIZE (5.0f)
#define MAX_DISPLACEMENT (1.0f)
#define DISPLACEMENT_SIGN_LIMIT (0.3f)
#define MAX_ITER (200)
#define NUM_ITER_AT_A_TIME (1)
/* Map general information */
#define MAP_SIZE (10.0f)
#define MAP_NUM_VERTICES (80)
#define MAP_NUM_TOTAL_VERTICES (MAP_NUM_VERTICES*MAP_NUM_VERTICES)
#define MAP_NUM_LINES (3* (MAP_NUM_VERTICES - 1) * (MAP_NUM_VERTICES - 1) + \
2 * (MAP_NUM_VERTICES - 1))
/**********************************************************************
* Default shader programs
*********************************************************************/
static const char* vertex_shader_text =
"#version 150\n"
"uniform mat4 project;\n"
"uniform mat4 modelview;\n"
"in float x;\n"
"in float y;\n"
"in float z;\n"
"\n"
"void main()\n"
"{\n"
" gl_Position = project * modelview * vec4(x, y, z, 1.0);\n"
"}\n";
static const char* fragment_shader_text =
"#version 150\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
" color = vec4(0.2, 1.0, 0.2, 1.0); \n"
"}\n";
/**********************************************************************
* Values for shader uniforms
*********************************************************************/
/* Frustum configuration */
static GLfloat view_angle = 45.0f;
static GLfloat aspect_ratio = 4.0f/3.0f;
static GLfloat z_near = 1.0f;
static GLfloat z_far = 100.f;
/* Projection matrix */
static GLfloat projection_matrix[16] = {
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
/* Model view matrix */
static GLfloat modelview_matrix[16] = {
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
/**********************************************************************
* Heightmap vertex and index data
*********************************************************************/
static GLfloat map_vertices[3][MAP_NUM_TOTAL_VERTICES];
static GLuint map_line_indices[2*MAP_NUM_LINES];
/* Store uniform location for the shaders
* Those values are setup as part of the process of creating
* the shader program. They should not be used before creating
* the program.
*/
static GLuint mesh;
static GLuint mesh_vbo[4];
/**********************************************************************
* OpenGL helper functions
*********************************************************************/
/* Creates a shader object of the specified type using the specified text
*/
static GLuint make_shader(GLenum type, const char* text)
{
GLuint shader;
GLint shader_ok;
GLsizei log_length;
char info_log[8192];
shader = glCreateShader(type);
if (shader != 0)
{
glShaderSource(shader, 1, (const GLchar**)&text, NULL);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &shader_ok);
if (shader_ok != GL_TRUE)
{
fprintf(stderr, "ERROR: Failed to compile %s shader\n", (type == GL_FRAGMENT_SHADER) ? "fragment" : "vertex" );
glGetShaderInfoLog(shader, 8192, &log_length,info_log);
fprintf(stderr, "ERROR: \n%s\n\n", info_log);
glDeleteShader(shader);
shader = 0;
}
}
return shader;
}
/* Creates a program object using the specified vertex and fragment text
*/
static GLuint make_shader_program(const char* vs_text, const char* fs_text)
{
GLuint program = 0u;
GLint program_ok;
GLuint vertex_shader = 0u;
GLuint fragment_shader = 0u;
GLsizei log_length;
char info_log[8192];
vertex_shader = make_shader(GL_VERTEX_SHADER, vs_text);
if (vertex_shader != 0u)
{
fragment_shader = make_shader(GL_FRAGMENT_SHADER, fs_text);
if (fragment_shader != 0u)
{
/* make the program that connect the two shader and link it */
program = glCreateProgram();
if (program != 0u)
{
/* attach both shader and link */
glAttachShader(program, vertex_shader);
glAttachShader(program, fragment_shader);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &program_ok);
if (program_ok != GL_TRUE)
{
fprintf(stderr, "ERROR, failed to link shader program\n");
glGetProgramInfoLog(program, 8192, &log_length, info_log);
fprintf(stderr, "ERROR: \n%s\n\n", info_log);
glDeleteProgram(program);
glDeleteShader(fragment_shader);
glDeleteShader(vertex_shader);
program = 0u;
}
}
}
else
{
fprintf(stderr, "ERROR: Unable to load fragment shader\n");
glDeleteShader(vertex_shader);
}
}
else
{
fprintf(stderr, "ERROR: Unable to load vertex shader\n");
}
return program;
}
/**********************************************************************
* Geometry creation functions
*********************************************************************/
/* Generate vertices and indices for the heightmap
*/
static void init_map(void)
{
int i;
int j;
int k;
GLfloat step = MAP_SIZE / (MAP_NUM_VERTICES - 1);
GLfloat x = 0.0f;
GLfloat z = 0.0f;
/* Create a flat grid */
k = 0;
for (i = 0 ; i < MAP_NUM_VERTICES ; ++i)
{
for (j = 0 ; j < MAP_NUM_VERTICES ; ++j)
{
map_vertices[0][k] = x;
map_vertices[1][k] = 0.0f;
map_vertices[2][k] = z;
z += step;
++k;
}
x += step;
z = 0.0f;
}
#if DEBUG_ENABLED
for (i = 0 ; i < MAP_NUM_TOTAL_VERTICES ; ++i)
{
printf ("Vertice %d (%f, %f, %f)\n",
i, map_vertices[0][i], map_vertices[1][i], map_vertices[2][i]);
}
#endif
/* create indices */
/* line fan based on i
* i+1
* | / i + n + 1
* | /
* |/
* i --- i + n
*/
/* close the top of the square */
k = 0;
for (i = 0 ; i < MAP_NUM_VERTICES -1 ; ++i)
{
map_line_indices[k++] = (i + 1) * MAP_NUM_VERTICES -1;
map_line_indices[k++] = (i + 2) * MAP_NUM_VERTICES -1;
}
/* close the right of the square */
for (i = 0 ; i < MAP_NUM_VERTICES -1 ; ++i)
{
map_line_indices[k++] = (MAP_NUM_VERTICES - 1) * MAP_NUM_VERTICES + i;
map_line_indices[k++] = (MAP_NUM_VERTICES - 1) * MAP_NUM_VERTICES + i + 1;
}
for (i = 0 ; i < (MAP_NUM_VERTICES - 1) ; ++i)
{
for (j = 0 ; j < (MAP_NUM_VERTICES - 1) ; ++j)
{
int ref = i * (MAP_NUM_VERTICES) + j;
map_line_indices[k++] = ref;
map_line_indices[k++] = ref + 1;
map_line_indices[k++] = ref;
map_line_indices[k++] = ref + MAP_NUM_VERTICES;
map_line_indices[k++] = ref;
map_line_indices[k++] = ref + MAP_NUM_VERTICES + 1;
}
}
#ifdef DEBUG_ENABLED
for (k = 0 ; k < 2 * MAP_NUM_LINES ; k += 2)
{
int beg, end;
beg = map_line_indices[k];
end = map_line_indices[k+1];
printf ("Line %d: %d -> %d (%f, %f, %f) -> (%f, %f, %f)\n",
k / 2, beg, end,
map_vertices[0][beg], map_vertices[1][beg], map_vertices[2][beg],
map_vertices[0][end], map_vertices[1][end], map_vertices[2][end]);
}
#endif
}
static void generate_heightmap__circle(float* center_x, float* center_y,
float* size, float* displacement)
{
float sign;
/* random value for element in between [0-1.0] */
*center_x = (MAP_SIZE * rand()) / (1.0f * RAND_MAX);
*center_y = (MAP_SIZE * rand()) / (1.0f * RAND_MAX);
*size = (MAX_CIRCLE_SIZE * rand()) / (1.0f * RAND_MAX);
sign = (1.0f * rand()) / (1.0f * RAND_MAX);
sign = (sign < DISPLACEMENT_SIGN_LIMIT) ? -1.0f : 1.0f;
*displacement = (sign * (MAX_DISPLACEMENT * rand())) / (1.0f * RAND_MAX);
}
/* Run the specified number of iterations of the generation process for the
* heightmap
*/
static void update_map(int num_iter)
{
assert(num_iter > 0);
while(num_iter)
{
/* center of the circle */
float center_x;
float center_z;
float circle_size;
float disp;
size_t ii;
generate_heightmap__circle(¢er_x, ¢er_z, &circle_size, &disp);
disp = disp / 2.0f;
for (ii = 0u ; ii < MAP_NUM_TOTAL_VERTICES ; ++ii)
{
GLfloat dx = center_x - map_vertices[0][ii];
GLfloat dz = center_z - map_vertices[2][ii];
GLfloat pd = (2.0f * (float) sqrt((dx * dx) + (dz * dz))) / circle_size;
if (fabs(pd) <= 1.0f)
{
/* tx,tz is within the circle */
GLfloat new_height = disp + (float) (cos(pd*3.14f)*disp);
map_vertices[1][ii] += new_height;
}
}
--num_iter;
}
}
/**********************************************************************
* OpenGL helper functions
*********************************************************************/
/* Create VBO, IBO and VAO objects for the heightmap geometry and bind them to
* the specified program object
*/
static void make_mesh(GLuint program)
{
GLuint attrloc;
glGenVertexArrays(1, &mesh);
glGenBuffers(4, mesh_vbo);
glBindVertexArray(mesh);
/* Prepare the data for drawing through a buffer inidices */
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mesh_vbo[3]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint)* MAP_NUM_LINES * 2, map_line_indices, GL_STATIC_DRAW);
/* Prepare the attributes for rendering */
attrloc = glGetAttribLocation(program, "x");
glBindBuffer(GL_ARRAY_BUFFER, mesh_vbo[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * MAP_NUM_TOTAL_VERTICES, &map_vertices[0][0], GL_STATIC_DRAW);
glEnableVertexAttribArray(attrloc);
glVertexAttribPointer(attrloc, 1, GL_FLOAT, GL_FALSE, 0, 0);
attrloc = glGetAttribLocation(program, "z");
glBindBuffer(GL_ARRAY_BUFFER, mesh_vbo[2]);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * MAP_NUM_TOTAL_VERTICES, &map_vertices[2][0], GL_STATIC_DRAW);
glEnableVertexAttribArray(attrloc);
glVertexAttribPointer(attrloc, 1, GL_FLOAT, GL_FALSE, 0, 0);
attrloc = glGetAttribLocation(program, "y");
glBindBuffer(GL_ARRAY_BUFFER, mesh_vbo[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * MAP_NUM_TOTAL_VERTICES, &map_vertices[1][0], GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(attrloc);
glVertexAttribPointer(attrloc, 1, GL_FLOAT, GL_FALSE, 0, 0);
}
/* Update VBO vertices from source data
*/
static void update_mesh(void)
{
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(GLfloat) * MAP_NUM_TOTAL_VERTICES, &map_vertices[1][0]);
}
/**********************************************************************
* GLFW callback functions
*********************************************************************/
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
switch(key)
{
case GLFW_KEY_ESCAPE:
/* Exit program on Escape */
glfwSetWindowShouldClose(window, GLFW_TRUE);
break;
}
}
static void error_callback(int error, const char* description)
{
fprintf(stderr, "Error: %s\n", description);
}
int main(int argc, char** argv)
{
GLFWwindow* window;
int iter;
double dt;
double last_update_time;
int frame;
float f;
GLint uloc_modelview;
GLint uloc_project;
int width, height;
GLuint shader_program;
glfwSetErrorCallback(error_callback);
if (!glfwInit())
exit(EXIT_FAILURE);
glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
window = glfwCreateWindow(800, 600, "GLFW OpenGL3 Heightmap demo", NULL, NULL);
if (! window )
{
glfwTerminate();
exit(EXIT_FAILURE);
}
/* Register events callback */
glfwSetKeyCallback(window, key_callback);
glfwMakeContextCurrent(window);
gladLoadGL(glfwGetProcAddress);
/* Prepare opengl resources for rendering */
shader_program = make_shader_program(vertex_shader_text, fragment_shader_text);
if (shader_program == 0u)
{
glfwTerminate();
exit(EXIT_FAILURE);
}
glUseProgram(shader_program);
uloc_project = glGetUniformLocation(shader_program, "project");
uloc_modelview = glGetUniformLocation(shader_program, "modelview");
/* Compute the projection matrix */
f = 1.0f / tanf(view_angle / 2.0f);
projection_matrix[0] = f / aspect_ratio;
projection_matrix[5] = f;
projection_matrix[10] = (z_far + z_near)/ (z_near - z_far);
projection_matrix[11] = -1.0f;
projection_matrix[14] = 2.0f * (z_far * z_near) / (z_near - z_far);
glUniformMatrix4fv(uloc_project, 1, GL_FALSE, projection_matrix);
/* Set the camera position */
modelview_matrix[12] = -5.0f;
modelview_matrix[13] = -5.0f;
modelview_matrix[14] = -20.0f;
glUniformMatrix4fv(uloc_modelview, 1, GL_FALSE, modelview_matrix);
/* Create mesh data */
init_map();
make_mesh(shader_program);
/* Create vao + vbo to store the mesh */
/* Create the vbo to store all the information for the grid and the height */
/* setup the scene ready for rendering */
glfwGetFramebufferSize(window, &width, &height);
glViewport(0, 0, width, height);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
/* main loop */
frame = 0;
iter = 0;
last_update_time = glfwGetTime();
while (!glfwWindowShouldClose(window))
{
++frame;
/* render the next frame */
glClear(GL_COLOR_BUFFER_BIT);
glDrawElements(GL_LINES, 2* MAP_NUM_LINES , GL_UNSIGNED_INT, 0);
/* display and process events through callbacks */
glfwSwapBuffers(window);
glfwPollEvents();
/* Check the frame rate and update the heightmap if needed */
dt = glfwGetTime();
if ((dt - last_update_time) > 0.2)
{
/* generate the next iteration of the heightmap */
if (iter < MAX_ITER)
{
update_map(NUM_ITER_AT_A_TIME);
update_mesh();
iter += NUM_ITER_AT_A_TIME;
}
last_update_time = dt;
frame = 0;
}
}
glfwTerminate();
exit(EXIT_SUCCESS);
}