我想在显示器上绘制像素,这些像素在某些参数后经常变化.例如.如果红色和绿色像素发生碰撞,它们都会消失,等等.
在每一帧中,我必须操纵大约100-1000像素.我这里有一个多线程的方法,它不会给我30FPS(我想要的).目前,我在RAM中存储了一个像素阵列,其中包含所有像素并具有SDL_Surface.当数组中的像素发生变化时,它也会在Surface中发生变化,然后在完成所有操作后,会对屏幕进行blitting.我目前的做法太慢了,我对如何提高速度做了一些思考.
我目前的想法是：
>使用OpenGL直接在GPU上进行像素操作,一些论坛告诉我这比我目前的方法要慢“这不是GPU的工作方式”
>不要存储像素阵列,直接在RAM中存储BMP,操作它然后将其移动到SDL_Surface或SDL_Texture
解决方法
SDL_CreateTexture()w / SDL_TEXTUREACCESS_STREAMING SDL_UpdateTexture()似乎与正确的像素格式一起工作得很好.
在我的系统上使用默认渲染器：
Renderer name: direct3d Texture formats: SDL_PIXELFORMAT_ARGB8888 SDL_PIXELFORMAT_YV12 SDL_PIXELFORMAT_IYUV
(虽然opengl信息是相同的:)
Renderer name: opengl Texture formats: SDL_PIXELFORMAT_ARGB8888 SDL_PIXELFORMAT_YV12 SDL_PIXELFORMAT_IYUV
SDL_PIXELFORMAT_ARGB8888给我~1ms /帧：
#include <SDL2/SDL.h>
#include <SDL2/SDL_render.h>
#include <iostream>
#include <vector>
using namespace std;
int main( int argc,char** argv )
{
SDL_Init( SDL_INIT_EVERYTHING );
atexit( SDL_Quit );
SDL_Window* window = SDL_CreateWindow
(
"SDL2",SDL_WINDOWPOS_UNDEFINED,600,SDL_WINDOW_SHOWN
);
SDL_Renderer* renderer = SDL_CreateRenderer
(
window,-1,SDL_RENDERER_ACCELERATED
);
SDL_RendererInfo info;
SDL_GetRendererInfo( renderer,&info );
cout << "Renderer name: " << info.name << endl;
cout << "Texture formats: " << endl;
for( Uint32 i = 0; i < info.num_texture_formats; i++ )
{
cout << SDL_GetPixelFormatName( info.texture_formats[i] ) << endl;
}
const unsigned int texWidth = 1024;
const unsigned int texHeight = 1024;
SDL_Texture* texture = SDL_CreateTexture
(
renderer,SDL_PIXELFORMAT_ARGB8888,SDL_TEXTUREACCESS_STREAMING,texWidth,texHeight
);
vector< unsigned char > pixels( texWidth * texHeight * 4,0 );
SDL_Event event;
bool running = true;
while( running )
{
const Uint64 start = SDL_GetPerformanceCounter();
SDL_SetRenderDrawColor( renderer,SDL_ALPHA_OPAQUE );
SDL_RenderClear( renderer );
while( SDL_PollEvent( &event ) )
{
if( ( SDL_QUIT == event.type ) ||
( SDL_KEYDOWN == event.type && SDL_SCANCODE_ESCAPE == event.key.keysym.scancode ) )
{
running = false;
break;
}
}
// splat down some random pixels
for( unsigned int i = 0; i < 1000; i++ )
{
const unsigned int x = rand() % texWidth;
const unsigned int y = rand() % texHeight;
const unsigned int offset = ( texWidth * 4 * y ) + x * 4;
pixels[ offset + 0 ] = rand() % 256; // b
pixels[ offset + 1 ] = rand() % 256; // g
pixels[ offset + 2 ] = rand() % 256; // r
pixels[ offset + 3 ] = SDL_ALPHA_OPAQUE; // a
}
//unsigned char* lockedPixels;
//int pitch;
//SDL_LockTexture
// (
// texture,// NULL,// reinterpret_cast< void** >( &lockedPixels ),// &pitch
// );
//std::copy( pixels.begin(),pixels.end(),lockedPixels );
//SDL_UnlockTexture( texture );
SDL_UpdateTexture
(
texture,NULL,&pixels[0],texWidth * 4
);
SDL_RenderCopy( renderer,texture,NULL );
SDL_RenderPresent( renderer );
const Uint64 end = SDL_GetPerformanceCounter();
const static Uint64 freq = SDL_GetPerformanceFrequency();
const double seconds = ( end - start ) / static_cast< double >( freq );
cout << "Frame time: " << seconds * 1000.0 << "ms" << endl;
}
SDL_DestroyRenderer( renderer );
SDL_DestroyWindow( window );
SDL_Quit();
}
确保您没有启用vsync(在驱动程序中强制执行,运行合成器等),否则所有帧时间将为~16ms(或者您的显示刷新设置为).
