Even if there are several classes to draw tile maps, I wanted to test 3 options and see the difference of performance:
- filling a map using Vertex
- pregenerate an image and use it as chunk
- use vertexArray
As I thought, just using vertex was going to be slow, so I thought about pre-rendering bigger chunks and using them to save draw() calls.
What was my surprise when I saw the test results (debug mode)...
Filling a 800x600 window, with 32x32 tiles (and a simple chunk of 800x600)
- filling a map using Vertex (475 calls): 4706 ms
- pregenerated image and used as chunk (1 call): 4442ms
- vertexArray (1 call to draw): 57 ms
Why the big difference between using only 1 800x600 image and calling once to draw but using 1900 vertices?
My common sense says that [1 draw / 800x600px / 4 vertices] should be faster than [1 draw / 800x600px / 1900 vertices]
In release mode the results are quite different...
- filling a map using Vertex (475 calls): 544 ms
- pregenerated image and used as chunk (1 call): 7ms
- vertexArray (1 call to draw): 5399 ms
But again, I don't know why the vertexArray (1 call / 1900 vertices) is much slower than the Vertex call (475 calls / 1900 vertices)
Here is the code of the test, if you wanna try...
sf::Clock clock;
// prepare vertices[4]
sf::Texture* tilesTexture = ResourceManager::getTexture("tiles.png");
sf::Vertex vertices1[4];
vertices1[0].position = sf::Vector2f(0, 0);
vertices1[1].position = sf::Vector2f(31, 0);
vertices1[2].position = sf::Vector2f(31, 31);
vertices1[3].position = sf::Vector2f(0, 31);
vertices1[0].texCoords = sf::Vector2f(0, 0);
vertices1[1].texCoords = sf::Vector2f(31, 0);
vertices1[2].texCoords = sf::Vector2f(31, 31);
vertices1[3].texCoords = sf::Vector2f(0, 31);
sf::RenderStates VertexStates;
VertexStates.texture = tilesTexture;
// test vertices[4]
clock.restart();
for(int x=0; x<25; x++)
{
for(int y=0; y<19; y++)
{
vertices1[0].position = sf::Vector2f(32*x, 32*y);
vertices1[1].position = sf::Vector2f(32*(x+1), 32*y);
vertices1[2].position = sf::Vector2f(32*(x+1), 32*(y+1));
vertices1[3].position = sf::Vector2f(32*x, 32*(y+1));
window.draw(vertices1, 4, sf::Quads, VertexStates);
}
}
cout << "vertex[4]: " << clock.getElapsedTime().asMicroseconds() << endl;
// prepare 1 draw with a 800x600 image
sf::Texture* fondo = ResourceManager::getTexture("bg800x600.png");
vertices1[0].position = sf::Vector2f(0, 0);
vertices1[1].position = sf::Vector2f(799, 0);
vertices1[2].position = sf::Vector2f(799, 599);
vertices1[3].position = sf::Vector2f(0, 599);
vertices1[0].texCoords = sf::Vector2f(0, 0);
vertices1[1].texCoords = sf::Vector2f(799, 0);
vertices1[2].texCoords = sf::Vector2f(799, 599);
vertices1[3].texCoords = sf::Vector2f(0, 599);
// test the image chunk
clock.restart();
VertexStates.texture = fondo;
window.draw(vertices1, 4, sf::Quads, VertexStates);
cout << "chunk800x600: " << clock.getElapsedTime().asMicroseconds() << endl;
// prepare the VertexArray call
VertexStates.texture = tilesTexture;
sf::VertexArray vertices2(sf::Quads, 25*19*4);
for(int x=0; x<25; x++)
{
for(int y=0; y<19; y++)
{
vertices2[(x + y*25)*4].position = sf::Vector2f(32*x, 32*y);
vertices2[(x + y*25)*4+1].position = sf::Vector2f(32*(x+1), 32*y);
vertices2[(x + y*25)*4+2].position = sf::Vector2f(32*(x+1), 32*(y+1));
vertices2[(x + y*25)*4+3].position = sf::Vector2f(32*x, 32*(y+1));
int i = rand()%9;
int j = rand()%9;
vertices2[(x + y*25)*4].texCoords = sf::Vector2f(i*32, 32*j);
vertices2[(x + y*25)*4+1].texCoords = sf::Vector2f(32*(i+1), 32*j);
vertices2[(x + y*25)*4+2].texCoords = sf::Vector2f(32*(i+1), 32*(j+1));
vertices2[(x + y*25)*4+3].texCoords = sf::Vector2f(32*i, 32*(j+1));
}
}
// test the VertexArray call
clock.restart();
window.draw(vertices2, VertexStates);
cout << "vertexArray: " << clock.getElapsedTime().asMicroseconds() << endl;
BTW
bg800x600.png is a 800x600 image, and
tiles.png a 256x256 image.
