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Expand rasterization rules

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Miloslav Číž 2019-05-04 01:04:33 +02:00
parent b77fbb38b2
commit 8c4809e9d9
1 changed files with 21 additions and 11 deletions
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s3l.h
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@ -65,19 +65,29 @@
Coordinates of pixels on screen start typically at the top left, from [0,0]. Coordinates of pixels on screen start typically at the top left, from [0,0].
Rasterization rules are to be the same as in OpenGL or DirectX: Triangle rasterization rules are these (mostly same as OpenGL, D3D etc.):
- Pixel centers are at integer coordinates. - Let's define:
- Pixel is rasterized if its center is inside the primitive (e.g. a triangle) - left side: not exactly horizontal, and on the left side of triangle
OR - top side: exactly horizontal and above the other two sides
if its center is exactly on the primitive's side, which is either left - right side: not left side nor top side
(no exactly horizontal and on the left side of triangle) or top (exactly - Pixel centers are at integer coordinates and triangle for drawing are
horizontal and above the other two edges) specified with integer coordinates of pixel centers.
- A pixel is rasterized:
- if its center is inside the triangle OR
- if its center is exactly on the triangle side which is either left or top
and at the same time is not on the side that's right (case of a triangle
that's on a single line) OR
- if its center is exactly on the triangle corner of sides neither of which
is right.
These rules imply e.g.: These rules imply among others:
- Triangles of points that lie on a single line are not rasterized. - Adjacent triangles don't have any overlapping pixels, nor gaps between.
- A single "long" triangle can be rasterized as non-continuous. - Triangles of points that lie on a single line are NOT rasterized.
- A single "long" triangle CAN be rasterized as non-continuous.
- Bottom most corner (or side) of a triangle is never rasterized if specified
with integer coordinates.
*/ */
#ifndef S3L_H #ifndef S3L_H
@ -666,7 +676,7 @@ void S3L_drawTriangle(
return; return;
} }
// triangle mode // triangle mode -- TODO: maybe move to the top as this is most common?
S3L_ScreenCoord S3L_ScreenCoord
tPointX, tPointY, // top triangle point coords tPointX, tPointY, // top triangle point coords