138 lines
2.9 KiB
C
138 lines
2.9 KiB
C
/**
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* Draw a series of textured quads after each quad, use glTexSubImage()
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* to change one row of the texture image.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <GL/glew.h>
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#include <GL/glut.h>
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static GLint Win = 0;
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static GLuint Tex = 0;
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static void Init(void)
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{
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fprintf(stderr, "GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
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fflush(stderr);
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glGenTextures(1, &Tex);
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glBindTexture(GL_TEXTURE_2D, Tex);
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glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
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glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
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glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
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glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
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glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
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}
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static void Reshape(int width, int height)
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{
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float ar = (float) width / height;
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glViewport(0, 0, width, height);
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glMatrixMode(GL_PROJECTION);
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glLoadIdentity();
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glOrtho(-ar, ar, -1.0, 1.0, -1.0, 1.0);
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glMatrixMode(GL_MODELVIEW);
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}
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static void Key(unsigned char key, int x, int y)
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{
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if (key == 27) {
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glDeleteTextures(1, &Tex);
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glutDestroyWindow(Win);
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exit(1);
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}
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glutPostRedisplay();
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}
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static void Draw(void)
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{
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GLubyte tex[16][16][4];
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GLubyte row[16][4];
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int i, j;
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for (i = 0; i < 16; i++) {
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for (j = 0; j < 16; j++) {
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if ((i + j) & 1) {
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tex[i][j][0] = 128;
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tex[i][j][1] = 128;
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tex[i][j][2] = 128;
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tex[i][j][3] = 255;
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}
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else {
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tex[i][j][0] = 255;
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tex[i][j][1] = 255;
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tex[i][j][2] = 255;
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tex[i][j][3] = 255;
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}
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}
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}
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for (i = 0; i < 16; i++) {
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row[i][0] = 255;
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row[i][1] = 0;
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row[i][2] = 0;
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row[i][3] = 255;
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}
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glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 16, 16, 0,
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GL_RGBA, GL_UNSIGNED_BYTE, tex);
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glEnable(GL_TEXTURE_2D);
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glClear(GL_COLOR_BUFFER_BIT);
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for (i = 0; i < 9; i++) {
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glPushMatrix();
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glTranslatef(-4.0 + i, 0, 0);
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glScalef(0.5, 0.5, 1.0);
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glBegin(GL_QUADS);
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glTexCoord2f(1,0);
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glVertex3f( 0.9, -0.9, 0.0);
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glTexCoord2f(1,1);
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glVertex3f( 0.9, 0.9, 0.0);
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glTexCoord2f(0,1);
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glVertex3f(-0.9, 0.9, 0.0);
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glTexCoord2f(0,0);
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glVertex3f(-0.9, -0.9, 0.0);
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glEnd();
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glPopMatrix();
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/* replace a row of the texture image with red texels */
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if (i * 2 < 16)
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glTexSubImage2D(GL_TEXTURE_2D, 0, 0, i*2, 16, 1,
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GL_RGBA, GL_UNSIGNED_BYTE, row);
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}
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glutSwapBuffers();
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}
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int main(int argc, char **argv)
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{
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glutInit(&argc, argv);
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glutInitWindowSize(900, 200);
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glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
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Win = glutCreateWindow(*argv);
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if (!Win) {
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exit(1);
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}
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glewInit();
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Init();
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glutReshapeFunc(Reshape);
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glutKeyboardFunc(Key);
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glutDisplayFunc(Draw);
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glutMainLoop();
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return 0;
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}
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