fading visuals

blending does not converge to bg color

main.cpp

@@ -103,23 +103,23 @@ int main() try {
 
 	// no clue who owns this
 	auto* texture = SDL_CreateTexture(
-		renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_TARGET, width,
+		renderer, SDL_PIXELFORMAT_RGB888, SDL_TEXTUREACCESS_TARGET, width,
 		height
 	);
 	sdl_check(SDL_SetRenderTarget(renderer, texture));
-	sdl_check(SDL_SetRenderDrawColor(renderer, 0xdb, 0xd7, 0xc0, SDL_ALPHA_OPAQUE));
+	sdl_check(
+		SDL_SetRenderDrawColor(renderer, 0xff, 0xff, 0xff, SDL_ALPHA_OPAQUE)
+	);
 	sdl_check(SDL_RenderClear(renderer));
-	sdl_check(SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_BLEND));
-	sdl_check(SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 2));
 
-		SDL_Point pos{.x = width / 2, .y = height / 2};
+	SDL_Point pos{.x = width / 2, .y = height / 2};
 	constexpr SDL_Point directions[] = {
 		{.x = -1, .y = 0}, {.x = 1, .y = 0}, {.x = 0, .y = -1}, {.x = 0, .y = 1}
 	};
 
 	std::mt19937_64 rne(std::random_device{}());
 	std::uniform_int_distribution dist(0, 3);
-	constexpr auto batchsize = 1000;
+	constexpr auto batchsize = 10000;
 
 	const auto start_time = clock::now();
 	auto next_poll_events_time = start_time;
@@ -149,13 +149,35 @@ int main() try {
 			pos = newpoint;
 			point_batch[step] = newpoint;
 		}
-		sdl_check(SDL_SetRenderTarget(renderer, texture));
-		sdl_check(SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_BLEND));
-		sdl_check(SDL_RenderDrawPoints(renderer, point_batch.data(), point_batch.size()));
 
+		///// Render image
+		sdl_check(SDL_SetRenderTarget(renderer, texture));
+		sdl_check(SDL_SetRenderDrawBlendMode(
+			renderer,
+			SDL_ComposeCustomBlendMode(
+				SDL_BLENDFACTOR_SRC_ALPHA, SDL_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
+				SDL_BLENDOPERATION_ADD, SDL_BLENDFACTOR_ZERO,
+				SDL_BLENDFACTOR_ONE, SDL_BLENDOPERATION_ADD
+			)
+		));
+		sdl_check(
+			SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, SDL_ALPHA_OPAQUE)
+		);
+		sdl_check(SDL_RenderDrawPoints(
+			renderer, point_batch.data(), point_batch.size()
+		));
+		sdl_check(SDL_SetRenderDrawColor(renderer, 0xff, 0xff, 0xff, 32));
+		sdl_check(SDL_RenderFillRect(renderer, nullptr));
+		// SDL_RenderCopy(renderer, fade_texture, nullptr, nullptr);
+
+		///// Render screen
 		sdl_check(SDL_SetRenderTarget(renderer, nullptr));
+		sdl_check(
+			SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, SDL_ALPHA_OPAQUE)
+		);
+		SDL_RenderClear(renderer);
 		sdl_check(SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE));
-		sdl_check(SDL_SetTextureBlendMode(texture, SDL_BLENDMODE_NONE));
+		// sdl_check(SDL_SetTextureBlendMode(texture, SDL_BLENDMODE_NONE));
 		sdl_check(SDL_RenderCopy(renderer, texture, nullptr, nullptr));
 		SDL_RenderPresent(renderer);
 	}