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examples: add examples/gg/many_thousands_of_circles.v, thanks to @xjunko, document how to use ctx.end(how:.passthru). (#18832)

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Delyan Angelov 2023-07-10 15:33:14 +03:00 committed by GitHub
parent f8e89ae91c
commit e7af25ec14
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2 changed files with 114 additions and 3 deletions

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@ -0,0 +1,56 @@
module main
import gg
import gx
import rand
const max_circles_per_pass = 1000
// prepare some random colors ahead of time
const colors = []gx.Color{len: max_circles_per_pass, init: gx.Color{
r: u8(index * 0 + rand.u8())
g: u8(index * 0 + rand.u8())
b: u8(index * 0 + rand.u8())
}}
fn frame(mut ctx gg.Context) {
// First pass, just clears the background:
ctx.begin()
ctx.end()
// We want to draw thousands of circles, but sokol has a limit for how
// many primitives can be in a single pass, and if you reach that limit
// you will not see *anything at all* for that pass.
// For the circles below, that limit is ~2520 circles per pass.
// To overcome this, we will use several passes instead, where each one
// will draw just 1000 circles.
// In other words, in total we will have 4 * 1000 = 4000 circles, drawn with
// 4 passes.
for i := 0; i < 4 * max_circles_per_pass; i += max_circles_per_pass {
ctx.begin()
for c in 0 .. max_circles_per_pass {
rx := rand.int_in_range(0, ctx.window.width) or { 0 }
ry := rand.int_in_range(0, ctx.window.height) or { 0 }
ctx.draw_circle_filled(rx, ry, 10, colors[c])
}
ctx.end(how: .passthru)
}
// The last pass, is for the fps overlay, that should be *always on top of everything*.
// Drawing it in a separate pass, guarantees, that it *will* be drawn, even if the drawing
// of all the other passes fail. Try increasing max_circles_per_pass to 3000 for example.
ctx.begin()
ctx.show_fps()
ctx.end(how: .passthru)
}
fn main() {
mut ctx := gg.new_context(
window_title: 'Many Thousands of Circles'
bg_color: gx.black
width: 600
height: 400
frame_fn: frame
)
ctx.run()
}

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@ -530,8 +530,56 @@ pub fn (ctx &Context) begin() {
sgl.ortho(0.0, f32(sapp.width()), f32(sapp.height()), 0.0, -1.0, 1.0) sgl.ortho(0.0, f32(sapp.width()), f32(sapp.height()), 0.0, -1.0, 1.0)
} }
// end finishes drawing for the context. pub enum EndEnum {
pub fn (ctx &Context) end() { clear
passthru
}
[params]
pub struct EndOptions {
how EndEnum
}
const dontcare_pass = gfx.PassAction{
colors: [
gfx.ColorAttachmentAction{
action: .dontcare
value: gfx.Color{1.0, 1.0, 1.0, 1.0}
},
gfx.ColorAttachmentAction{
action: .dontcare
value: gfx.Color{1.0, 1.0, 1.0, 1.0}
},
gfx.ColorAttachmentAction{
action: .dontcare
value: gfx.Color{1.0, 1.0, 1.0, 1.0}
},
gfx.ColorAttachmentAction{
action: .dontcare
value: gfx.Color{1.0, 1.0, 1.0, 1.0}
},
]!
}
// end finishes all the drawing for the context ctx.
// All accumulated draw calls before ctx.end(), will be done in a separate Sokol pass.
//
// Note: each Sokol pass, has a limit on the number of draw calls, that can be done in it.
// Once that limit is reached, the whole pass will not draw anything, which can be frustrating.
//
// To overcome this limitation, you may use *several passes*, when you want to make thousands
// of draw calls (for example, if you need to draw thousands of circles/rectangles/sprites etc),
// where each pass will render just a limited amount of primitives.
//
// In the context of the gg module (without dropping to using sgl and gfx directly), it means,
// that you will need a new pair of ctx.begin() and ctx.end() calls, surrounding all the draw
// calls, that should be done in each pass.
//
// The default ctx.end() is equivalent to ctx.end(how:.clear). It will erase the existing
// rendered content with the background color, before drawing anything else.
// You can call ctx.end(how:.passthru) for a pass, that *will not* erase the previously
// rendered content in the context.
pub fn (ctx &Context) end(options EndOptions) {
$if show_fps ? { $if show_fps ? {
ctx.show_fps() ctx.show_fps()
} $else { } $else {
@ -539,7 +587,14 @@ pub fn (ctx &Context) end() {
ctx.show_fps() ctx.show_fps()
} }
} }
gfx.begin_default_pass(ctx.clear_pass, sapp.width(), sapp.height()) match options.how {
.clear {
gfx.begin_default_pass(ctx.clear_pass, sapp.width(), sapp.height())
}
.passthru {
gfx.begin_default_pass(gg.dontcare_pass, sapp.width(), sapp.height())
}
}
sgl.draw() sgl.draw()
gfx.end_pass() gfx.end_pass()
gfx.commit() gfx.commit()