Here is a short video showing what I meant by "it doesn't work well for all view angles".

There is a visible square pattern. It puzzled me for a while. I thought the grass was not uniformly spread. Until I noticed it disappears when looking in the opposite direction.

What I think now, is that grass is created per ground chunk (confirmed by the docs, actually). And the order of mesh creation is the same for each chunk (along the Z axis apparently)

#GameDev #Godot

My current theory is that what happens when looking in the good direction is that it will first draw the ones that are far, and then those closer which hide the far ones, and so on. This works fine.

But when looking in the other direction, it first draws those which are near, then those farther which given the perspective will hide the top of the closer one, then draws those farther which hide the top and so on, until reaching the edge of the square (those have the top visible and seem higher)

At the end of the video I've made zooms in/out to show another interesting thing: when close enough it works better, the close grass is not hidden by the one farther. This is because I've enabled depth_prepass_alpha. I have not studied in detail how it works, but it should use the depth test for parts of the grass that are solid, making sure closer is drawn on top.

Using alpha scissor instead doesn't work well and just makes a mess of shimmering pixels when the camera moves (awful aliasing).

The problem I think is that when zooming out, grass becomes blurry thanks to mipmaps (which is a good thing to avoid aliasing), but then as multiple grass blades occupy the same texel, it gets an intermediate alpha value (which is fine as well).

Problem is, it's not fully opaque so won't use depth test to make sure it's drawn above the farther grass. So basically this technique for order-independent alpha blend doesn't work in this situation.

Finding a good order-independent translucency rendering (or anything that gives good anti-aliasing results) is my main focus for now, but after that there are lots of remaining things to improve.

For now there is a single mesh with single texture repeated, I'll need to add a bit of variety, including less frequent plants that may stand out a bit more (flowers etc.)

There is also an issue with the ground underneath whose color is too different.

Performances are a concern too.

And grass planes almost parallel with the view direction give weird lighting, I think I may need to actually fade them out as they don't really contribute (i.e. each pair of crossed planes would fade from one to the other depending on the view angle)

And I may need to add self-shadowing and/or ambient occlusion.

Still a lot of things to fix and improve before it's "good enough"...