/***************************************************************** textureAlpha.c by Dave Pape 9 Feb 2003 This program demonstrates using alpha with textures. It draws a solid sphere, with two different textured squares in front of it. One square is drawn with a simple RGB texture, with a 50% transparent alpha defined in the square's material. The other square is drawn with an RGBA texture, where the alpha in the texture map varies from texel to texel; this gives the square varying transparency over its surface. *****************************************************************/ #include #include #include #include #include #include GLfloat viewRotY = 0, viewRotX = 0, cameraDistance = 5; GLuint textureID1, textureID2; void drawEverything(void); void defineTextures(void); void initLight(void); void checkGLError(char *); void key(unsigned char k, int x, int y); void specialkey(int k, int x, int y); int main(int argc, char *argv[]) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH); glutInitWindowSize(512,512); glutCreateWindow(argv[0]); glutDisplayFunc(drawEverything); glutKeyboardFunc(key); glutSpecialFunc(specialkey); defineTextures(); glutMainLoop(); return 0; } void drawEverything(void) { GLfloat opaqueWhite[] = { 1.0, 1.0, 1.0, 1.0 }; GLfloat transparentWhite[] = { 1.0, 1.0, 1.0, 0.5 }; glClearColor(0.5, 0.7, 1.0, 0.0); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(50.0, 1.0, 0.1, 100.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); initLight(); glTranslatef(0.0, 0.0, -cameraDistance); glRotatef(viewRotX, 1.0, 0.0, 0.0); glRotatef(viewRotY, 0.0, 1.0, 0.0); glPushMatrix(); glTranslatef(0.0, 0.0, -5.0); glutSolidSphere(3.0, 16, 8); glPopMatrix(); glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_TEXTURE_2D); /*************** CODE OF INTEREST ******************************/ /* Bind the RGBA texture to the first square. The square's */ /* material has a constant alpha of 1. */ /* */ glMaterialfv(GL_FRONT, GL_DIFFUSE, opaqueWhite); /**/ glBindTexture(GL_TEXTURE_2D, textureID1); /**/ glNormal3f(0.0, 0.0, 1.0); glBegin(GL_QUADS); glTexCoord2i(0,0); glVertex3f(-2.0, -1.0, 0.0); glTexCoord2i(1,0); glVertex3f(-0.1, -1.0, 0.0); glTexCoord2i(1,1); glVertex3f(-0.1, 1.0, 0.0); glTexCoord2i(0,1); glVertex3f(-2.0, 1.0, 0.0); glEnd(); /*************** CODE OF INTEREST ******************************/ /* Bind the RGB texture to the second square. The square's */ /* material has a constant alpha of 0.5. */ /* */ glMaterialfv(GL_FRONT, GL_DIFFUSE, transparentWhite); /**/ glBindTexture(GL_TEXTURE_2D, textureID2); /**/ glNormal3f(0.0, 0.0, 1.0); glBegin(GL_QUADS); glTexCoord2i(0,0); glVertex3f(0.1, -1.0, 0.0); glTexCoord2i(1,0); glVertex3f(2.0, -1.0, 0.0); glTexCoord2i(1,1); glVertex3f(2.0, 1.0, 0.0); glTexCoord2i(0,1); glVertex3f(0.1, 1.0, 0.0); glEnd(); glDisable(GL_TEXTURE_2D); glDisable(GL_BLEND); glutSwapBuffers(); checkGLError("end-of-frame"); } #define IMAGE_HEIGHT 128 #define IMAGE_WIDTH 128 GLubyte textureImage[IMAGE_HEIGHT][IMAGE_WIDTH][4]; /*************** CODE OF INTEREST ******************************/ /* Define the two textures. One will be RGBA, the other */ /* just RGB. Note that both textures use the same image */ /* data array, so both set their format to GL_RGBA. */ /* However, the second texture sets its internal format to */ /* RGB, so OpenGL will ignore the alpha data. */ /* */ void defineTextures(void) { int i,j; for (i=0; i < IMAGE_HEIGHT; i++) for (j=0; j < IMAGE_WIDTH; j++) { textureImage[i][j][0] = (i>j) * 255; textureImage[i][j][1] = ((IMAGE_HEIGHT-i) > j) * 255; textureImage[i][j][2] = (j >= (IMAGE_WIDTH/2)) * 255; textureImage[i][j][3] = (int)((sin(i*0.2) * sin(j*0.2) + 1.0) * 127.5); } glGenTextures(1, &textureID1); glBindTexture(GL_TEXTURE_2D, textureID1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, IMAGE_WIDTH, IMAGE_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, textureImage); glGenTextures(1, &textureID2); glBindTexture(GL_TEXTURE_2D, textureID2); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, IMAGE_WIDTH, IMAGE_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, textureImage); glBindTexture(GL_TEXTURE_2D, 0); } /***************************************************************/ void initLight(void) { GLfloat white[4] = { 1, 1, 1, 1 }; GLfloat lightPos[4] = {-1, 1, 1, 0}; glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glLightfv(GL_LIGHT0, GL_DIFFUSE, white); glLightfv(GL_LIGHT0, GL_POSITION, lightPos); } void checkGLError(char *prefix) { GLenum err = glGetError(); if (err != GL_NO_ERROR) printf("%s GL error '%s'\n",prefix,gluErrorString(err)); } void key(unsigned char k, int x, int y) { if (k == 27) exit(0); else if (k == '-') cameraDistance += 1; else if (k == '=') cameraDistance -= 1; glutPostRedisplay(); } void specialkey(int k, int x, int y) { if (k == GLUT_KEY_LEFT) viewRotY += 3; else if (k == GLUT_KEY_RIGHT) viewRotY -= 3; else if (k == GLUT_KEY_UP) viewRotX += 3; else if (k == GLUT_KEY_DOWN) viewRotX -= 3; glutPostRedisplay(); }