diff options
| -rw-r--r-- | src/mesa/drivers/dri/i965/gen8_viewport_state.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/src/mesa/drivers/dri/i965/gen8_viewport_state.c b/src/mesa/drivers/dri/i965/gen8_viewport_state.c index b366246fba3..b5171e08770 100644 --- a/src/mesa/drivers/dri/i965/gen8_viewport_state.c +++ b/src/mesa/drivers/dri/i965/gen8_viewport_state.c @@ -71,10 +71,24 @@ gen8_upload_sf_clip_viewport(struct brw_context *brw) * maximum screen space coordinates of a small object may larger, but we * have no way to enforce the object size other than through clipping. * - * If you're surprised that we set clip to -gbx to +gbx and it seems like - * we'll end up with 16384 wide, note that for a 8192-wide render target, - * we'll end up with a normal (-1, 1) clip volume that just covers the - * drawable. + * The goal is to create the maximum sized guardband (8K x 8K) with the + * viewport rectangle in the center of the guardband. This looks weird + * because the hardware wants coordinates that are scaled to the viewport + * in NDC. In other words, an 8K x 8K viewport would have [-1,1] for X and Y. + * A 4K viewport would be [-2,2], 2K := [-4,4] etc. + * + * -------------------------------- + * |Guardband | + * | | + * | ------------ | + * | |viewport | | + * | | | | + * | | | | + * | |__________| | + * | | + * | | + * |______________________________| + * */ const float maximum_guardband_extent = 8192; float gbx = maximum_guardband_extent / ctx->ViewportArray[i].Width; |