opengl.rar_OpenGL多边形_OpenGl画点

// Triangle.c // OpenGL SuperBible, Chapter 4 // Demonstrates OpenGL Triangle Fans, backface culling, and depth testing // Program by Richard S. Wright Jr. #include "../../Common/OpenGLSB.h" // System and OpenGL Stuff #include <math.h> // Define a constant for the value of PI #define GL_PI 3.1415f // Rotation amounts static GLfloat xRot = 0.0f; static GLfloat yRot = 0.0f; // Flags for effects // Flags for effects int iCull = 0; int iOutline = 0; int iDepth = 0; /////////////////////////////////////////////////////////////////////////////// // Reset flags as appropriate in response to menu selections void ProcessMenu(int value) { switch(value) { case 1: iDepth = !iDepth; break; case 2: iCull = !iCull; break; case 3: iOutline = !iOutline; default: break; } glutPostRedisplay(); } // Called to draw scene void RenderScene(void) { GLfloat x,y,angle; // Storage for coordinates and angles int iPivot = 1; // Used to flag alternating colors // Clear the window and the depth buffer glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Turn culling on if flag is set if(iCull) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE); // Enable depth testing if flag is set if(iDepth) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST); // Draw back side as a polygon only, if flag is set if(iOutline) glPolygonMode(GL_BACK,GL_LINE); else glPolygonMode(GL_BACK,GL_FILL); // Save matrix state and do the rotation glPushMatrix(); glRotatef(xRot, 1.0f, 0.0f, 0.0f); glRotatef(yRot, 0.0f, 1.0f, 0.0f); // Begin a triangle fan glBegin(GL_TRIANGLE_FAN); // Pinnacle of cone is shared vertex for fan, moved up Z axis // to produce a cone instead of a circle glVertex3f(0.0f, 0.0f, 75.0f); // Loop around in a circle and specify even points along the circle // as the vertices of the triangle fan for(angle = 0.0f; angle < (2.0f*GL_PI); angle += (GL_PI/8.0f)) { // Calculate x and y position of the next vertex x = 50.0f*sin(angle); y = 50.0f*cos(angle); // Alternate color between red and green if((iPivot %2) == 0) glColor3f(0.0f, 1.0f, 0.0f); else glColor3f(1.0f, 0.0f, 0.0f); // Increment pivot to change color next time iPivot++; // Specify the next vertex for the triangle fan glVertex2f(x, y); } // Done drawing fan for cone glEnd(); // Begin a new triangle fan to cover the bottom glBegin(GL_TRIANGLE_FAN); // Center of fan is at the origin glVertex2f(0.0f, 0.0f); for(angle = 0.0f; angle < (2.0f*GL_PI); angle += (GL_PI/8.0f)) { // Calculate x and y position of the next vertex x = 50.0f*sin(angle); y = 50.0f*cos(angle); // Alternate color between red and green if((iPivot %2) == 0) glColor3f(0.0f, 1.0f, 0.0f); else glColor3f(1.0f, 0.0f, 0.0f); // Increment pivot to change color next time iPivot++; // Specify the next vertex for the triangle fan glVertex2f(x, y); } // Done drawing the fan that covers the bottom glEnd(); // Restore transformations glPopMatrix(); // Flush drawing commands glutSwapBuffers(); } // This function does any needed initialization on the rendering // context. void SetupRC() { // Black background glClearColor(0.0f, 0.0f, 0.0f, 1.0f ); // Set drawing color to green glColor3f(0.0f, 1.0f, 0.0f); // Set color shading model to flat glShadeModel(GL_FLAT); // Clock wise wound polygons are front facing, this is reversed // because we are using triangle fans glFrontFace(GL_CW); } void SpecialKeys(int key, int x, int y) { if(key == GLUT_KEY_UP) xRot-= 5.0f; if(key == GLUT_KEY_DOWN) xRot += 5.0f; if(key == GLUT_KEY_LEFT) yRot -= 5.0f; if(key == GLUT_KEY_RIGHT) yRot += 5.0f; if(key > 356.0f) xRot = 0.0f; if(key < -1.0f) xRot = 355.0f; if(key > 356.0f) yRot = 0.0f; if(key < -1.0f) yRot = 355.0f; // Refresh the Window glutPostRedisplay(); } void ChangeSize(int w, int h) { GLfloat nRange = 100.0f; // Prevent a divide by zero if(h == 0) h = 1; // Set Viewport to window dimensions glViewport(0, 0, w, h); // Reset projection matrix stack glMatrixMode(GL_PROJECTION); glLoadIdentity(); // Establish clipping volume (left, right, bottom, top, near, far) if (w <= h) glOrtho (-nRange, nRange, -nRange*h/w, nRange*h/w, -nRange, nRange); else glOrtho (-nRange*w/h, nRange*w/h, -nRange, nRange, -nRange, nRange); // Reset Model view matrix stack glMatrixMode(GL_MODELVIEW); glLoadIdentity(); } int main(int argc, char* argv[]) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); glutCreateWindow("Triangle Culling Example"); // Create the Menu glutCreateMenu(ProcessMenu); glutAddMenuEntry("Toggle depth test",1); glutAddMenuEntry("Toggle cull backface",2); glutAddMenuEntry("Toggle outline back",3); glutAttachMenu(GLUT_RIGHT_BUTTON); glutReshapeFunc(ChangeSize); glutSpecialFunc(SpecialKeys); glutDisplayFunc(RenderScene); SetupRC(); glutMainLoop(); return 0; }