How to draw Ice Cream with OpenGL - c

Question

As the question, how to draw the 3d ice cream? I have draw a cone and a ball. But the ball cannot fit inside the cone.....I try with many way, but the ball is either bihind the cone or whole one infornt the cone... Can anyone exust me on this. I have follow the note from lecturer but still not able to get.
#include <Windows.h>
#include <gl/GL.h>
#include <math.h>
#include <time.h>
#include <gl/GLU.h>
#pragma comment (lib, "OpenGL32.lib")
#pragma comment (lib, "GLU32.lib")
#define WINDOW_TITLE "OpenGL Window"
LRESULT WINAPI WindowProcedure(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
break;
}
return DefWindowProc(hWnd, msg, wParam, lParam);
}
//--------------------------------------------------------------------
bool initPixelFormat(HDC hdc)
{
PIXELFORMATDESCRIPTOR pfd;
ZeroMemory(&pfd, sizeof(PIXELFORMATDESCRIPTOR));
pfd.cAlphaBits = 8;
pfd.cColorBits = 32;
pfd.cDepthBits = 24;
pfd.cStencilBits = 0;
pfd.dwFlags = PFD_DOUBLEBUFFER | PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW;
pfd.iLayerType = PFD_MAIN_PLANE;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
pfd.nVersion = 1;
// choose pixel format returns the number most similar pixel format available
int n = ChoosePixelFormat(hdc, &pfd);
// set pixel format returns whether it sucessfully set the pixel format
if (SetPixelFormat(hdc, n, &pfd))
{
return true;
}
else
{
return false;
}
}
//--------------------------------------------------------------------
void display()
{
glPushMatrix();
glRotatef(120, 1.0, 0, 0);
GLUquadricObj * cylinder = NULL;
cylinder = gluNewQuadric();
glColor3f(1, 0, 0);
gluQuadricDrawStyle(cylinder, GLU_FILL);
gluCylinder(cylinder, 0.52, 0.0, 2.0, 30, 20);
gluDeleteQuadric(cylinder);
GLUquadricObj * sphere = NULL;
sphere = gluNewQuadric();
glColor3f(1, 1, 1);
gluQuadricDrawStyle(sphere, GLU_LINE);
gluSphere(sphere, 0.5, 20, 20);
gluDeleteQuadric(sphere);
glPopMatrix();
}
//--------------------------------------------------------------------
int WINAPI WinMain(HINSTANCE hInst, HINSTANCE, LPSTR, int nCmdShow)
{
WNDCLASSEX wc;
ZeroMemory(&wc, sizeof(WNDCLASSEX));
wc.cbSize = sizeof(WNDCLASSEX);
wc.hInstance = GetModuleHandle(NULL);
wc.lpfnWndProc = WindowProcedure;
wc.lpszClassName = WINDOW_TITLE;
wc.style = CS_HREDRAW | CS_VREDRAW;
if (!RegisterClassEx(&wc)) return false;
HWND hWnd = CreateWindow(WINDOW_TITLE, WINDOW_TITLE, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, 800, 640,
NULL, NULL, wc.hInstance, NULL);
//--------------------------------
// Initialize window for OpenGL
//--------------------------------
HDC hdc = GetDC(hWnd);
// initialize pixel format for the window
initPixelFormat(hdc);
// get an openGL context
HGLRC hglrc = wglCreateContext(hdc);
// make context current
if (!wglMakeCurrent(hdc, hglrc)) return false;
//--------------------------------
// End initialization
//--------------------------------
ShowWindow(hWnd, nCmdShow);
MSG msg;
ZeroMemory(&msg, sizeof(msg));
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-2.0f, +3.0f, -2.0f, +2.0f, -10.0f, +10.0f);
while (true)
{
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
if (msg.message == WM_QUIT) break;
TranslateMessage(&msg);
DispatchMessage(&msg);
}
display();
SwapBuffers(hdc);
}
UnregisterClass(WINDOW_TITLE, wc.hInstance);
return true;
}
//--------------------------------------------------------------------

Answer 1

Note, that drawing by glBegin/glEnd sequences, the fixed function pipeline matrix stack and fixed function pipeline per vertex light model, is deprecated since decades.
Read about Fixed Function Pipeline and see Vertex Specification and Shader for a state of the art way of rendering.
anyway, In the PIXELFORMATDESCRIPTOR the depth buffer is proper specified:
pfd.cDepthBits = 24;
now you have to use the depth buffer.
Side note, the number of the color buffer bits should be 24 instead of 32 see the documentation of cColorBits:
Specifies the number of color bitplanes in each color buffer. For RGBA pixel types, it is the size of the color buffer, excluding the alpha bitplanes. For color-index pixels, it is the size of the color-index buffer.
To use the depth buffer the Depth Test has to be enabled by glEnable.
Further the color buffer and the depth buffer of the default framebuffer has to be cleared at the begin of every frame by glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT )
void display()
{
glEnable( GL_DEPTH_TEST );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glPushMatrix();
glRotatef(120, 1.0, 0, 0);
GLUquadricObj * cylinder = NULL;
cylinder = gluNewQuadric();
glColor3f(1, 0.5, 0);
gluQuadricDrawStyle(cylinder, GLU_FILL);
gluCylinder(cylinder, 0.52, 0.0, 2.0, 30, 20);
gluDeleteQuadric(cylinder);
GLUquadricObj * sphere = NULL;
sphere = gluNewQuadric();
glColor3f(1, 1, 0.5);
gluQuadricDrawStyle(sphere, GLU_FILL);
gluSphere(sphere, 0.5, 20, 20);
gluDeleteQuadric(sphere);
glPopMatrix();
}
See the preview, where i changed the gluQuadricDrawStyle for the sphere from GLU_LINE to GL_FILL: