Search code examples
opengl3drenderingdepth

Rendering glitch with GL_DEPTH_TEST and transparent textures

From one angle my shrubs look like this:

From the other, they look like this:

My theory is that when looking at the shrubs from the first angle, all the blocks behind the shrub have already been drawn, so when it comes to draw the shrub, it just draws them overtop.

From the other angle, however, it's basically trying to draw the shrub first, and then when it goes to draw the block behind the shrub, it checks the depth buffer and sees that there's something already blocking the view of the block, so it doesn't render it, causing the navy blue squares (my clear color).

I really have no idea how to fix this issue though. Disabling the depth test causes all kinds of other errors. Is there some way to flag the vertex or polygon as having transparency so that it knows it still needs to render what's behind?

Found this. Is this the only solution? To separate my transparent and opaque blocks, and then manually sort them on the CPU pretty much every single frame because the player can move around? There has to be a way to delegate this to the GPU...

Solution

  • That link (and sorting on CPU) is for alpha blending. If you need only Alpha Testing (not Blending), then you don't need to sort anything. Just enable alpha test, keeping depth test enabled, and everything will be rendered fine.

    See here: http://www.opengl.org/wiki/Transparency_Sorting You need "Alpha test" that requires alpha testing, not "Standard translucent" that requires sorting.