Some rendering details

2D rendering works in layers. When you use new_draw_queues() or use a post-processing effect, a new set of draw queues will be created, meaning that anything new that is drawn will be drawn over everything drawn previously, no matter what.

In the case of a post-processing effect this is almost always what you want, but if it isn’t you may need to be careful of what order your drawing functions run. If this is a problem for you, decouple your update functions from drawing functions that don’t mutate state, so that drawing functions can run in any order.

Within a single draw queue, objects drawn in screen-space will always be drawn above objects drawn in world space. You can overwrite this using a new set of draw queues.

Scissors

A scissor is basically a filter to a rectangle of the screen, it will prevent rendering of any pixels outside of that rectangle for the duration of that scissor being active. You can add and remove them with push_scissor and pop_scissor. Pushing a scissor when another scissor is already active will set the scissor to the intersection of both of them, so things will only be drawn if they are inside both rectangles.

#![allow(unused)]
fn main() {
// this will draw a semi-circle
push_scissor(Area::new(vec2(window_center().x, 0.0), window_size()).to_rect());
draw_circle(window_center(), 500.0, Color::WHITE);
pop_scissor();
}

Culling

By default, no culling will be applied to objects drawn offscreen (that are not visible), as this would incur a runtime cost for all objects drawn, that may not be desired. If you want to have objects drawn offscreen be culled for better performance, you should use the World2D struct, which lets you spawn anything that implements the Entity2D trait into the world, and have it only be drawn and/or updated when onscreen.

See: scene module

See also: /examples/world.rs for an example on how to use the API, by rewriting the physics.rs example in a nicer way.