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authorBen Widawsky <[email protected]>2014-07-02 17:07:34 -0700
committerBen Widawsky <[email protected]>2014-08-10 17:13:36 -0700
commit1a20e38ccfdc581a158a3e9f96e25465f2ab55df (patch)
treef68906c46e603d8399d3aec1421c635c4aeaf4b0
parent109d420f42b66224366f4604d1235204101abb37 (diff)
i965: Simplify viewport extents programming on GEN8
Viewport extents are a 3rd rectangle that defines which pixels get discarded as part of the rasterization process. The actual pixels drawn to the screen are an intersection of the drawing rectangle, the viewport extents, and the scissor rectangle. It permits the use of guardband clipping in all cases (see later patch). The actual pixels drawn to the screen are an intersection of the drawing rectangle, the viewport extents, and the scissor rectangle. Scissor rectangle is not super important for this discussion as it should always help do the right thing provided the programmer uses it. switch (viewport dimensions, drawrect dimension) { case viewport > drawing rectangle: no effects; break; case viewport == drawing rectangle: no effects; break; case viewport < drawing rectangle: Pixels (after the viewport transformation but before expensive rastersizing and shading operations) which are outside of the viewport are discarded. } I am unable to find a test case where this improves performance, but in all my testing it doesn't hurt performance, and intuitively, it should not ever hurt performance. It also permits us to use the guardband more freely (see upcoming patch). v2: Updating commit message. v3: Commit message updates requested by Ken Reviewed-by: Kenneth Graunke <[email protected]>
-rw-r--r--src/mesa/drivers/dri/i965/gen8_viewport_state.c24
1 files changed, 15 insertions, 9 deletions
diff --git a/src/mesa/drivers/dri/i965/gen8_viewport_state.c b/src/mesa/drivers/dri/i965/gen8_viewport_state.c
index b5171e08770..04a45300b4b 100644
--- a/src/mesa/drivers/dri/i965/gen8_viewport_state.c
+++ b/src/mesa/drivers/dri/i965/gen8_viewport_state.c
@@ -100,17 +100,23 @@ gen8_upload_sf_clip_viewport(struct brw_context *brw)
vp[10] = -gby; /* y-min */
vp[11] = gby; /* y-max */
- /* _NEW_SCISSOR | _NEW_VIEWPORT | _NEW_BUFFERS: Screen Space Viewport */
+ /* _NEW_SCISSOR | _NEW_VIEWPORT | _NEW_BUFFERS: Screen Space Viewport
+ * The hardware will take the intersection of the drawing rectangle,
+ * scissor rectangle, and the viewport extents. We don't need to be
+ * smart, and can therefore just program the viewport extents.
+ */
+ float viewport_Xmax = ctx->ViewportArray[i].X + ctx->ViewportArray[i].Width;
+ float viewport_Ymax = ctx->ViewportArray[i].Y + ctx->ViewportArray[i].Height;
if (render_to_fbo) {
- vp[12] = ctx->DrawBuffer->_Xmin;
- vp[13] = ctx->DrawBuffer->_Xmax - 1;
- vp[14] = ctx->DrawBuffer->_Ymin;
- vp[15] = ctx->DrawBuffer->_Ymax - 1;
+ vp[12] = ctx->ViewportArray[i].X;
+ vp[13] = viewport_Xmax - 1;
+ vp[14] = ctx->ViewportArray[i].Y;
+ vp[15] = viewport_Ymax - 1;
} else {
- vp[12] = ctx->DrawBuffer->_Xmin;
- vp[13] = ctx->DrawBuffer->_Xmax - 1;
- vp[14] = ctx->DrawBuffer->Height - ctx->DrawBuffer->_Ymax;
- vp[15] = ctx->DrawBuffer->Height - ctx->DrawBuffer->_Ymin - 1;
+ vp[12] = ctx->ViewportArray[i].X;
+ vp[13] = viewport_Xmax - 1;
+ vp[14] = ctx->DrawBuffer->Height - viewport_Ymax;
+ vp[15] = ctx->DrawBuffer->Height - ctx->ViewportArray[i].Y - 1;
}
vp += 16;