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#include <stdlib.h>
#include <stdio.h>
#include <GL/glew.h>
#include <GL/glfw.h>
static void pushModelview()
{
GLenum prev_matrix_mode;
glGetIntegerv(GL_MATRIX_MODE, &prev_matrix_mode);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glMatrixMode(prev_matrix_mode);
}
static void popModelview()
{
GLenum prev_matrix_mode;
glGetIntegerv(GL_MATRIX_MODE, &prev_matrix_mode);
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(prev_matrix_mode);
}
static const GLchar *vertex_shader_source =
"#version 120\n"
"void main()"
"{"
" gl_Position = gl_ProjectionMatrix * gl_ModelViewMatrix * gl_Vertex;"
" gl_TexCoord[0] = gl_MultiTexCoord0;"
" gl_FrontColor = gl_Color;"
" gl_BackColor = gl_Color;"
"}\0";
GLuint shaderVertex = 0;
static const GLchar *fragment_shader_source =
"#version 120\n"
"uniform sampler2D texCMYK;\n"
"uniform sampler2D texRGB;\n"
"uniform float T;\n"
"const float pi = 3.14159265;\n"
"void main()\n"
"{\n"
" float ts = gl_TexCoord[0].s;\n"
" vec2 mod_texcoord = gl_TexCoord[0].st*vec2(1., 2.) + vec2(0, -0.5 + 0.5*sin(T + 1.5*ts*pi));\n"
" if( mod_texcoord.t < 0. || mod_texcoord.t > 1. ) { discard; }\n"
" gl_FragColor.rgb = -texture2D(texCMYK, mod_texcoord).xyz + texture2D(texRGB, gl_TexCoord[0].st).xyz;\n"
"}\n\0";
GLuint shaderFragment = 0;
GLuint shaderProgram = 0;
#define TEX_CMYK_WIDTH 2
#define TEX_CMYK_HEIGHT 2
GLubyte textureDataCMYK[TEX_CMYK_WIDTH * TEX_CMYK_HEIGHT][3] = {
{0x00, 0xff, 0xff}, {0xff, 0x00, 0xff},
{0xff, 0xff, 0x00}, {0x00, 0x00, 0x00}
};
GLuint texCMYK = 0;
#define TEX_RGB_WIDTH 2
#define TEX_RGB_HEIGHT 2
GLubyte textureDataRGB[TEX_RGB_WIDTH * TEX_RGB_HEIGHT][3] = {
{0x00, 0x00, 0xff}, {0xff, 0xff, 0xff},
{0xff, 0x00, 0x00}, {0x00, 0xff, 0x00}
};
GLuint texRGB = 0;
/* 6----7
/| /|
3----2 |
| 5--|-4
|/ |/
0----1
*/
GLfloat cube_vertices[][8] = {
/* X Y Z Nx Ny Nz S T */
{-1.0, -1.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0}, // 0
{ 1.0, -1.0, 1.0, 0.0, 0.0, 1.0, 1.0, 0.0}, // 1
{ 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 1.0, 1.0}, // 2
{-1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0}, // 3
{ 1.0, -1.0, -1.0, 0.0, 0.0, -1.0, 0.0, 0.0}, // 4
{-1.0, -1.0, -1.0, 0.0, 0.0, -1.0, 1.0, 0.0}, // 5
{-1.0, 1.0, -1.0, 0.0, 0.0, -1.0, 1.0, 1.0}, // 6
{ 1.0, 1.0, -1.0, 0.0, 0.0, -1.0, 0.0, 1.0}, // 7
{-1.0, -1.0, -1.0, -1.0, 0.0, 0.0, 0.0, 0.0}, // 5
{-1.0, -1.0, 1.0, -1.0, 0.0, 0.0, 1.0, 0.0}, // 0
{-1.0, 1.0, 1.0, -1.0, 0.0, 0.0, 1.0, 1.0}, // 3
{-1.0, 1.0, -1.0, -1.0, 0.0, 0.0, 0.0, 1.0}, // 6
{ 1.0, -1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0}, // 1
{ 1.0, -1.0, -1.0, 1.0, 0.0, 0.0, 1.0, 0.0}, // 4
{ 1.0, 1.0, -1.0, 1.0, 0.0, 0.0, 1.0, 1.0}, // 7
{ 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 1.0}, // 2
{-1.0, -1.0, -1.0, 0.0, -1.0, 0.0, 0.0, 0.0}, // 5
{ 1.0, -1.0, -1.0, 0.0, -1.0, 0.0, 1.0, 0.0}, // 4
{ 1.0, -1.0, 1.0, 0.0, -1.0, 0.0, 1.0, 1.0}, // 1
{-1.0, -1.0, 1.0, 0.0, -1.0, 0.0, 0.0, 1.0}, // 0
{-1.0, 1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 0.0}, // 3
{ 1.0, 1.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0}, // 2
{ 1.0, 1.0, -1.0, 0.0, 1.0, 0.0, 1.0, 1.0}, // 7
{-1.0, 1.0, -1.0, 0.0, 1.0, 0.0, 0.0, 1.0}, // 6
};
static void draw_cube(void)
{
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glVertexPointer(3, GL_FLOAT, sizeof(GLfloat) * 8, &cube_vertices[0][0]);
glNormalPointer(GL_FLOAT, sizeof(GLfloat) * 8, &cube_vertices[0][3]);
glTexCoordPointer(2, GL_FLOAT, sizeof(GLfloat) * 8, &cube_vertices[0][6]);
glDrawArrays(GL_QUADS, 0, 24);
}
static void bind_sampler_to_unit_with_texture(GLchar const * const sampler_name, GLuint texture_unit, GLuint texture)
{
glActiveTexture(GL_TEXTURE0 + texture_unit);
glBindTexture(GL_TEXTURE_2D, texture);
GLuint loc_sampler = glGetUniformLocation(shaderProgram, sampler_name);
glUniform1i(loc_sampler, texture_unit);
}
static void display(double T)
{
int window_width, window_height;
glfwGetWindowSize(&window_width, &window_height);
if( !window_width || !window_height )
return;
const float window_aspect = (float)window_width / (float)window_height;
glDisable(GL_SCISSOR_TEST);
glClearColor(0.5, 0.5, 0.7, 1.0);
glClearDepth(1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glViewport(0, 0, window_width, window_height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-window_aspect, window_aspect, -1, 1, 2.5, 10);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0, 0, -5);
pushModelview();
glRotatef(T * 0.1 * 180, 0., 1., 0.);
glRotatef(T * 0.1 * 60, 1., 0., 0.);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glUseProgram(shaderProgram);
glUniform1f(glGetUniformLocation(shaderProgram, "T"), T);
bind_sampler_to_unit_with_texture("texCMYK", 0, texCMYK);
bind_sampler_to_unit_with_texture("texRGB", 1, texRGB);
draw_cube();
popModelview();
glfwSwapBuffers();
}
static int open_window(void)
{
#if 0
glfwWindowHint(GLFW_OPENGL_VERSION_MAJOR, 2);
glfwWindowHint(GLFW_OPENGL_VERSION_MINOR, 0);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);
#endif
if( glfwOpenWindow(0, 0, /* default size */
8, 8, 8, /* 8 bits per channel */
8, 24, 8, /* 8 alpha, 24 depth, 8 stencil */
GLFW_WINDOW) != GL_TRUE ) {
fputs("Could not open window.\n", stderr);
return 0;
}
if( glewInit() != GLEW_OK ) {
fputs("Could not initialize extensions.\n", stderr);
return 0;
}
return 1;
}
static int check_extensions(void)
{
if( !GLEW_ARB_vertex_shader ||
!GLEW_ARB_fragment_shader ) {
fputs("Required OpenGL functionality not supported by system.\n", stderr);
return 0;
}
return 1;
}
static int check_shader_compilation(GLuint shader)
{
GLint n;
glGetShaderiv(shader, GL_COMPILE_STATUS, &n);
if( n == GL_FALSE ) {
GLchar *info_log;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &n);
info_log = malloc(n);
glGetShaderInfoLog(shader, n, &n, info_log);
fprintf(stderr, "Shader compilation failed: %*s\n", n, info_log);
free(info_log);
return 0;
}
return 1;
}
static int init_resources(void)
{
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glGenTextures(1, &texCMYK);
glBindTexture(GL_TEXTURE_2D, texCMYK);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, TEX_CMYK_WIDTH, TEX_CMYK_HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, textureDataCMYK);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glGenTextures(1, &texRGB);
glBindTexture(GL_TEXTURE_2D, texRGB);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, TEX_RGB_WIDTH, TEX_RGB_HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, textureDataRGB);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
shaderVertex = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(shaderVertex, 1, (const GLchar**)&vertex_shader_source, NULL);
glCompileShader(shaderVertex);
if( !check_shader_compilation(shaderVertex) )
return 0;
shaderFragment = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(shaderFragment, 1, (const GLchar**)&fragment_shader_source, NULL);
glCompileShader(shaderFragment);
if( !check_shader_compilation(shaderFragment) )
return 0;
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, shaderVertex);
glAttachShader(shaderProgram, shaderFragment);
glLinkProgram(shaderProgram);
return 1;
}
static void main_loop(void)
{
glfwSetTime(0);
while( glfwGetWindowParam(GLFW_OPENED) == GL_TRUE ) {
display(glfwGetTime());
}
}
int main(int argc, char *argv[])
{
if( glfwInit() != GL_TRUE ) {
fputs("Could not initialize framework.\n", stderr);
return -1;
}
if( !open_window() )
return -1;
if( !check_extensions() )
return -1;
if( !init_resources() )
return -1;
main_loop();
glfwTerminate();
return 0;
}
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