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triangles, mostly
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tic80_rust/src/gfx/framebuffer.rs
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tic80_rust/src/gfx/framebuffer.rs
···
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// Filled triangle using scanline rasterization
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#[allow(clippy::too_many_arguments)]
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pub fn tri(&mut self, mut x1: i32, mut y1: i32, mut x2: i32, mut y2: i32, mut x3: i32, mut y3: i32, color: u8) {
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pub fn tri(&mut self, x0: i32, y0: i32, x1: i32, y1: i32, x2: i32, y2: i32, color: u8) {
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let c = color & 0x0F;
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// Sort by y, then x
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if y2 < y1 || (y2 == y1 && x2 < x1) { std::mem::swap(&mut x1, &mut x2); std::mem::swap(&mut y1, &mut y2); }
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if y3 < y1 || (y3 == y1 && x3 < x1) { std::mem::swap(&mut x1, &mut x3); std::mem::swap(&mut y1, &mut y3); }
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if y3 < y2 || (y3 == y2 && x3 < x2) { std::mem::swap(&mut x2, &mut x3); std::mem::swap(&mut y2, &mut y3); }
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if y1 == y3 { return; }
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if y2 == y3 {
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// flat-bottom
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let inv1 = (x2 - x1) as f32 / (y2 - y1) as f32;
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let inv2 = (x3 - x1) as f32 / (y2 - y1) as f32;
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let mut cx1 = x1 as f32;
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let mut cx2 = x1 as f32;
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for y in y1..=y2 {
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self.hspan(cx1.floor() as i32, cx2.floor() as i32, y, c);
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cx1 += inv1;
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cx2 += inv2;
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}
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} else if y1 == y2 {
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// flat-top
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let inv1 = (x3 - x1) as f32 / (y3 - y1) as f32;
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let inv2 = (x3 - x2) as f32 / (y3 - y2) as f32;
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let mut cx1 = x1 as f32;
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let mut cx2 = x2 as f32;
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for y in y1..=y3 {
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self.hspan(cx1.floor() as i32, cx2.floor() as i32, y, c);
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cx1 += inv1;
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cx2 += inv2;
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}
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// Convert to CCW orientation for consistent edge tests
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let area = (x1 - x0) as i64 * (y2 - y0) as i64 - (x2 - x0) as i64 * (y1 - y0) as i64;
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let (v0x, v0y, v1x, v1y, v2x, v2y) = if area < 0 {
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(x0, y0, x2, y2, x1, y1)
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} else {
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// general: split at y2
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let x4 = x1 + (((y2 - y1) as f32) * ((x3 - x1) as f32) / ((y3 - y1) as f32)).floor() as i32;
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// flat-bottom part
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let inv1 = (x2 - x1) as f32 / (y2 - y1) as f32;
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let inv2 = (x4 - x1) as f32 / (y2 - y1) as f32;
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let mut cx1 = x1 as f32;
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let mut cx2 = x1 as f32;
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for y in y1..=y2 {
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self.hspan(cx1.floor() as i32, cx2.floor() as i32, y, c);
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cx1 += inv1;
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cx2 += inv2;
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}
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// flat-top part
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let inv1b = (x3 - x2) as f32 / (y3 - y2) as f32;
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let inv2b = (x3 - x4) as f32 / (y3 - y2) as f32;
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let mut cx1b = x2 as f32;
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let mut cx2b = x4 as f32;
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for y in y2..=y3 {
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self.hspan(cx1b.floor() as i32, cx2b.floor() as i32, y, c);
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cx1b += inv1b;
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cx2b += inv2b;
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(x0, y0, x1, y1, x2, y2)
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};
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// Bounding box (exclusive max per top-left rule)
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let min_x = v0x.min(v1x).min(v2x);
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let min_y = v0y.min(v1y).min(v2y);
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let max_x = v0x.max(v1x).max(v2x);
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let max_y = v0y.max(v1y).max(v2y);
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// Doubling coordinates to evaluate edge functions at pixel centers (x+0.5, y+0.5)
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let (ax2, ay2) = ((v0x as i64) * 2, (v0y as i64) * 2);
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let (bx2, by2) = ((v1x as i64) * 2, (v1y as i64) * 2);
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let (cx2, cy2) = ((v2x as i64) * 2, (v2y as i64) * 2);
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// Edge deltas
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let e0_dx = bx2 - ax2; let e0_dy = by2 - ay2; // v0->v1
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let e1_dx = cx2 - bx2; let e1_dy = cy2 - by2; // v1->v2
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let e2_dx = ax2 - cx2; let e2_dy = ay2 - cy2; // v2->v0
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// Top-left classification
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let e0_top_left = e0_dy > 0 || (e0_dy == 0 && e0_dx < 0);
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let e1_top_left = e1_dy > 0 || (e1_dy == 0 && e1_dx < 0);
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let e2_top_left = e2_dy > 0 || (e2_dy == 0 && e2_dx < 0);
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// Iterate over pixels in bounding box with top-left rule: y in [min_y, max_y), x in [min_x, max_x)
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for y in min_y..max_y {
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for x in min_x..max_x {
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let px = (x as i64) * 2 + 1;
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let py = (y as i64) * 2 + 1;
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// Edge functions
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let e0 = (py - ay2) * e0_dx - (px - ax2) * e0_dy;
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let e1 = (py - by2) * e1_dx - (px - bx2) * e1_dy;
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let e2 = (py - cy2) * e2_dx - (px - cx2) * e2_dy;
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// Apply top-left inclusion rules
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if (e0 > 0 || (e0 == 0 && e0_top_left))
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&& (e1 > 0 || (e1 == 0 && e1_top_left))
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&& (e2 > 0 || (e2 == 0 && e2_top_left))
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{
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let _ = self.set_pixel(x, y, c);
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}
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}
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}
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}