This falls under the "Triangle Rasterization Rules (Without Multisampling)" section:

"The light and dark gray covering of the pixels show them as groups of the pixels to indicate which triangle they are inside."

So, in the bottom left group of 3 triangles, pixels in the leftmost triangle are dark gray, pixels in the middle triangle are light gray, and pixels in the rightmost triangle are light gray.

I find it interesting that for the top right group of 2 triangles, the lower triangle does not "cover" any pixels and is this not colored. This shows how supersampling by averaging out sample values in a pixel can help prevent aliasing.

Hope this is correct and helps!

muminovic

Does the top edge need to be perfectly horizontal? i.e. both it's vertices/endpoints need to have the exact same y value for it to be considered a top edge?

chenwnicole

@muminovic I was also wondering whether the top edge has to be perfectly horizontal, turns out it does! Thanks @jenzou for the link. According to the link, "A top edge, is an edge that is exactly horizontal and is above the other edges."

I think the top left triangle helps illustrate this point: the third pixel on the top seems to be on the edge, but isn't in the triangle because the edge isn't perfectly horizontal, thus not a top edge.

are the different covered pixel color used to signified that they belong to different (adjacent) triangles?

I found the link to the source mentioned in the slide:

https://docs.microsoft.com/en-us/windows/desktop/direct3d11/d3d10-graphics-programming-guide-rasterizer-stage-rules

This falls under the "Triangle Rasterization Rules (Without Multisampling)" section:

"The light and dark gray covering of the pixels show them as groups of the pixels to indicate which triangle they are inside."

So, in the bottom left group of 3 triangles, pixels in the leftmost triangle are dark gray, pixels in the middle triangle are light gray, and pixels in the rightmost triangle are light gray.

I find it interesting that for the top right group of 2 triangles, the lower triangle does not "cover" any pixels and is this not colored. This shows how supersampling by averaging out sample values in a pixel can help prevent aliasing.

Hope this is correct and helps!

Does the top edge need to be perfectly horizontal? i.e. both it's vertices/endpoints need to have the exact same y value for it to be considered a top edge?

@muminovic I was also wondering whether the top edge has to be perfectly horizontal, turns out it does! Thanks @jenzou for the link. According to the link, "A top edge, is an edge that is exactly horizontal and is above the other edges."

I think the top left triangle helps illustrate this point: the third pixel on the top seems to be on the edge, but isn't in the triangle because the edge isn't perfectly horizontal, thus not a top edge.