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implement triangle drawing "optimizations"

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these don't actually improve performance at all judging from the
criterion benchmarks. lol.
This commit is contained in:
Gered 2023-04-01 14:24:29 -04:00
parent 67bcbec69b
commit 6689f31146
1 changed files with 28 additions and 14 deletions
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42
ggdt/src/graphics/bitmap/triangles.rs
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@ -4,7 +4,7 @@ use crate::math::vector2::Vector2;
#[inline]
fn cross(a: Vector2, b: Vector2, c: Vector2) -> f32 {
(c.x - a.x) * (b.y - a.y) - (c.y - a.y) * (b.x - a.x)
(b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x)
}
impl<PixelType: Pixel> Bitmap<PixelType> {
@ -55,9 +55,6 @@ impl<PixelType: Pixel> Bitmap<PixelType> {
// https://www.scratchapixel.com/lessons/3d-basic-rendering/rasterization-practical-implementation/rasterization-stage.html
// https://kitsunegames.com/post/development/2016/07/28/software-3d-rendering-in-javascript-pt2/
// TODO: optimize further. have had some trouble with some explanations of the optmizations presented in the
// linked article and the math presented. in particular i would prefer to have counter-clockwise vertex
// ordering but the math presented seems to only work as-is with clockwise ordering ... *grumble*
// TODO: implement fill rules, probably using top-left ordering as most 3d APIs do i guess
let min_x = a.x.min(b.x).min(c.x).floor() as i32;
@ -70,24 +67,41 @@ impl<PixelType: Pixel> Bitmap<PixelType> {
let max_x = std::cmp::min(self.clip_region().right(), max_x);
let max_y = std::cmp::min(self.clip_region().bottom(), max_y);
let a01 = a.y - b.y;
let b01 = b.x - a.x;
let a12 = b.y - c.y;
let b12 = c.x - b.x;
let a20 = c.y - a.y;
let b20 = a.x - c.x;
let p = Vector2::new(min_x as f32, min_y as f32);
let mut w0_row = cross(b, c, p);
let mut w1_row = cross(c, a, p);
let mut w2_row = cross(a, b, p);
let draw_width = (max_x - min_x + 1) as usize;
let next_row_inc = self.width() as usize;
let mut pixels = unsafe { self.pixels_at_mut_ptr_unchecked(min_x, min_y) };
for y in min_y..=max_y {
for _ in min_y..=max_y {
let mut w0 = w0_row;
let mut w1 = w1_row;
let mut w2 = w2_row;
let row_pixels = unsafe { std::slice::from_raw_parts_mut(pixels, draw_width) };
for (idx, pixel) in row_pixels.iter_mut().enumerate() {
let x = min_x + idx as i32;
let p = Vector2::new(x as f32, y as f32);
let w0 = cross(b, c, p);
let w1 = cross(c, a, p);
let w2 = cross(a, b, p);
if w0 >= 0.0 && w1 >= 0.0 && w2 >= 0.0 {
for pixel in row_pixels.iter_mut() {
if w0 < 0.0 && w1 < 0.0 && w2 < 0.0 {
pixel_fn(pixel, w0, w1, w2);
}
w0 += a12;
w1 += a20;
w2 += a01;
}
w0_row += b12;
w1_row += b20;
w2_row += b01;
pixels = unsafe { pixels.add(next_row_inc) };
}
}