谁能帮忙讲讲如何用C语言在窗口下实现动画效果的原理（点绘 不是图片）

我想绘制一个有动画效果的函数轨迹 但是因为函数计算量大 所以不能WM_PAINT直接重画
但是用计时器又解决不了重画问题

期待大家给以解决！！

先谢谢你

但是我事先说了哈
不是图片
是点绘

你的意思还是不太明白
我这有个程序 你看看能不能帮我改一下


#include <windows.h>
#include <math.h>

#define PI 3.14

int cxClient, cyClient ;
float i, j, x, y ;

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("SineWave") ;
MSG msg ;
WNDCLASS wndclass;
HWND hwnd ;

wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc= WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground= (HBRUSH) GetStockObject (LTGRAY_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;

if (!RegisterClass (&wndclass))
{
MessageBox ( NULL, TEXT ("Program requires Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}

hwnd = CreateWindow ( szAppName, TEXT ("美丽蝴蝶"),
WS_OVERLAPPEDWINDOW,
10, 10,
800, 600,
NULL, NULL, hInstance, NULL) ;

ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;

while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}

return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc ;
PAINTSTRUCT ps ;
RECT rect;
HBRUSH hBrush ;
HBITMAP bit;
HINSTANCE hinst ;

switch (message)
{
case WM_CREATE:
return 0 ;
case WM_SIZE:
cxClient = LOWORD (lParam) ;
cyClient = HIWORD (lParam) ;

InvalidateRect (hwnd, NULL, FALSE) ;
return 0;
case WM_PAINT:
hdc = BeginPaint (hwnd, &ps) ;
for(i = -6*PI;i < 6*PI;i +=0.01)
for(j = -3*PI;j < 3*PI;j += 0.01)
{
y = sin(i)*i*j+cyClient/2 ;
x = cos(i)*i*j+cxClient/2 ;
SetPixel(hdc
, x
, y
, RGB(i*6,255,j*5)) ;
}
EndPaint (hwnd, &ps) ;

return 0 ;

case WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;

}

return DefWindowProc (hwnd, message, wParam, lParam) ;

}