i have some questions about the project about dxr-sandbox-gi HOT 1 CLOSED

@Xiyinyue hello! I will try to explain what is happening here.

1. The "[-1,3]" you mentioned. Basically, it is a trick to render a quad (which is a slice of our propagation volume) only with 3 vertices by drawing a bigger triangle which is then "clipped" to a quad. This is efficient and common in full screen passes (we kinda have a fullscreen pass if we think from the "volume" perspective because its our render target). Here is a more detailed explanation: https://stackoverflow.com/questions/2588875/whats-the-best-way-to-draw-a-fullscreen-quad-in-opengl-3-2

2. I am not sure I am following your "there is no change for screenPos". SV_Position semantic which stores our screenPos in shader has to be in normalized coordinates; the pixel shader then receives screenPos which was automatically prepared/converted to pixel coordinates (thus [0,32] range which is the dimension of our volume).

In RenderDoc if you select a slice in the texture view and then debug a pixel from that slice, you should see proper values in shader debug (screenPos in [0,32], depthIndex = slice).

I hope it answers your questions. If you have more, feel free to ask!

from dxr-sandbox-gi.