SDL layered rendering system
Multi tool use
SDL layered rendering system
I would like help with building a layered rendering system in SDL2.
I have a first layer containing a map of Paris with its roads.
I need to draw a line between two points on this map - the problem occurs when the before state of this line does not disappear.
I need to draw this line over the map and keep this.
How do I make s a system to save the map state whithout any overlaid lines drawn, and such that frame by frame I can show the map with the new state of the line overlaid on top of this?
Use 2 textures one for the map the other for the line drawing. Render to these textures using SDL_SetRenderTarget and then draw the final textures into your window.
– Aram
Jul 1 at 8:04
I made this, now works fine, thanks !!
– Jardel Carvalho
Jul 1 at 17:39
1 Answer
1
Solved, below an example !! Thank you all
SDL_Window *window;
SDL_Renderer *render;
SDL_Texture *map; //map texture (my layer)
window = SDL_CreateWindow("Test window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
render = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
map = SDL_CreateTexture(render, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, 640, 480); //Creating a texture
/*Map is a red background stored in map texture*/
SDL_SetRenderDrawColor(render, 255, 0, 0, 255);
SDL_SetRenderTarget(render, map);
SDL_RenderClear(render);
SDL_SetRenderTarget(render, NULL);
/*Seting the line color*/
SDL_SetRenderDrawColor(render, 0, 255, 0, 255);
/*Coping the map texture to the render and drawing a green line on top of this*/
SDL_RenderCopy(render, map, NULL, NULL);
SDL_RenderDrawLine(render, 0, 0, 640, 480);
SDL_RenderPresent(render);
SDL_Delay(2000);
/*Another line*/
SDL_RenderCopy(render, map, NULL, NULL);
SDL_RenderDrawLine(render, 0, 480, 640, 0);
SDL_RenderPresent(render);
SDL_Delay(2000);
SDL_DestroyWindow(window);
SDL_DestroyRenderer(render);
SDL_Quit();
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Buffering. Render each layer to its own buffer then blit the buffers to the final render surface preserving transparency and perhaps using an alternative blending mode. You may take advantage of optimizations for 2D scrolling if present in the available hardware (I'm not familiar with the SDL API for that, though).
– Dai
Jul 1 at 8:01