C语言 重用纹理 SDL

Question

我正在制作我的第一个 SDL2 游戏，我有一个纹理，我在其中绘制我的游戏，但在每次渲染后纹理被空白，我需要保持我的原始纹理不变。

我很容易用表面做到这一点，但它太慢了。

我在这个纹理上绘制随机伪影，随着时间的推移而消失，我用SDL_RenderFill来着色纹理。

有人知道怎么做吗？

编辑：这是纹理渲染的代码

int gv_render(void) // This is called every 10ms
{
gv_lock;
int nexttimeout;
// Clear the screen
SDL_SetRenderTarget(renderer,NULL);
SDL_SetRenderDrawColor(renderer,0,0,0,255);
SDL_SetRenderDrawBlendMode(renderer,SDL_BLENDMODE_NONE);
SDL_RenderClear(renderer);
// Render view specific stuff
SDL_SetRenderTarget(renderer,gv_screen); // gv_screen is my screen texture
switch (player_view) { // I have multiple views
case pvsound:nexttimeout=wave_render();break; // <- THE 2ND FUNCTION /
};
SDL_RenderPresent(renderer);
// Final screen rendering
SDL_SetRenderTarget(renderer,NULL);
SDL_RenderCopy(renderer,gv_screen,NULL,NULL);
gv_unlock;
return nexttimeout;
};
int wave_render(void) // I (will) have multiple view modes
{
game_wave *currwave = firstwave; // First wave is the first element of a linked list
game_wave *prevwave = firstwave;  
map_block* block;
map_block* oldblock;
gv_lock;
// Load the old texture
SDL_RenderCopy(renderer,gv_screen,NULL,NULL);
SDL_SetRenderDrawBlendMode(renderer,SDL_BLENDMODE_BLEND);
// Dark the screen
SDL_SetRenderDrawColor(renderer,0,0,0,8);
SDL_RenderFillRect(renderer,NULL);
SDL_SetRenderDrawBlendMode(renderer,SDL_BLENDMODE_NONE);
// Now I travel my list
while (currwave) {
// Apply block info
/* skipped non graphics */
// Draw the wave point
uint8_t light; // Wave have a strong that decrease with time
if (currwave->strong>=1.0)
light = 255; // Over 1 it don't decrease
else light = currwave->strong*255; // Now they aren't fully white
SDL_SetRenderDrawColor(renderer,light,light,light,255);
SDL_RenderDrawPoint(renderer, currwave->xpos,currwave->ypos);
// Switch to next wave
prevwave = currwave; // There also code is the skipped part
currwave = currwave->next;
};
SDL_RenderPresent(renderer);
gv_unlock;
return 10;
};

'''

Answer 1

这似乎很复杂，正如 @david C. Rankin 所说，SDL 渲染器比 Surface 更快，但或多或少是只写的(SDL_RenderReadPixels和SDL_UpdateTexture可以在非实时情况下完成这项工作(。

我已经改变了我的方法，我在 256 个项目数组中使用带有入口点的像素坐标链表。

我的源代码现在是：

struct game_wave_point {
struct game_wave_point *next;
int x;
int y;  
};typedef struct game_wave_point game_wave_point;
game_wave_point* graph_waves[256] = {NULL,NULL,...};
wave_render(void)
{
game_wave *currwave = firstwave;
// Perform the darkening
int i;
uint8_t light;
for (i=1;i<=255;i++)
graph_waves[i-1] = graph_waves[i];
graph_waves[255] = NULL;
// Remove unvisible point
game_wave_point* newpoint;
while (graph_waves[0]) {
newpoint = graph_waves[0];
graph_waves[0] = newpoint->next;
free(newpoint);
};    
// Wave heartbeat...
while (currwave) {
/* blablabla */
// Add the drawing point
newpoint = malloc(sizeof(game_wave_point));
newpoint->next = graph_waves[light];
newpoint->x = currwave->xpos*pixelsperblock;
newpoint->y = currwave->ypos*pixelsperblock;
if ((newpoint->x<0)|(newpoint->y<0))
free(newpoint);
else graph_waves[light] = newpoint;
/* blablabla */
};
// Now perform the drawing
for (i=1;i<=255;i++) {
newpoint = graph_waves[i];
SDL_SetRenderDrawColor(renderer,i,i,i,255);
SDL_GetRenderDrawColor(renderer,&light,NULL,NULL,NULL);
while (newpoint) {
SDL_RenderDrawPoint(renderer,newpoint->x,newpoint->y);
newpoint = newpoint->next;
};
};
return 10;
};

这在我的计算机上效果很好(在我永远不会达到的情况下出现渐进式缓慢(。 接下来的优化可能会使用 Linux mremap(2( 和类似的方法执行，这将允许创建一个与 SDL_RenderDrawPoints 一起使用的简单数组，而不会在大数组上 realloc(( 变慢。