r600g: Implement POLYGON_OFFSET_UNITS_UNSCALED

Empirical tests show that the polygon offset
behaviour is entirely determined by the content of
the PA_SU_POLY_OFFSET states, and not by the depth buffer
format bound.

PA_SU_POLY_OFFSET seems to directly set the parameters of
the polygon offset formula, and setting 0 for
PA_SU_POLY_OFFSET_DB_FMT_CNTL (ie setting the unorm depth
bias behaviour with a scale of 2^0 = 1.0f) gives the unscaled
behaviour.

Signed-off-by: Axel Davy <[email protected]>
Reviewed-by: Marek Olšák <[email protected]>

1 files changed, 19 insertions, 16 deletions

diff --git a/src/gallium/drivers/r600/r600_state.c b/src/gallium/drivers/r600/r600_state.c
index 578aef992da..89a9f25b425 100644
--- a/src/gallium/drivers/r600/r600_state.c
+++ b/src/gallium/drivers/r600/r600_state.c
@@ -256,22 +256,24 @@ static void r600_emit_polygon_offset(struct r600_context *rctx, struct r600_atom
 	float offset_scale = state->offset_scale;
 	uint32_t pa_su_poly_offset_db_fmt_cntl = 0;
 
-	switch (state->zs_format) {
-	case PIPE_FORMAT_Z24X8_UNORM:
-	case PIPE_FORMAT_Z24_UNORM_S8_UINT:
-		offset_units *= 2.0f;
-		pa_su_poly_offset_db_fmt_cntl =
-			S_028DF8_POLY_OFFSET_NEG_NUM_DB_BITS((char)-24);
-		break;
-	case PIPE_FORMAT_Z16_UNORM:
-		offset_units *= 4.0f;
-		pa_su_poly_offset_db_fmt_cntl =
-			S_028DF8_POLY_OFFSET_NEG_NUM_DB_BITS((char)-16);
-		break;
-	default:
-		pa_su_poly_offset_db_fmt_cntl =
-			S_028DF8_POLY_OFFSET_NEG_NUM_DB_BITS((char)-23) |
-			S_028DF8_POLY_OFFSET_DB_IS_FLOAT_FMT(1);
+	if (!state->offset_units_unscaled) {
+		switch (state->zs_format) {
+		case PIPE_FORMAT_Z24X8_UNORM:
+		case PIPE_FORMAT_Z24_UNORM_S8_UINT:
+			offset_units *= 2.0f;
+			pa_su_poly_offset_db_fmt_cntl =
+				S_028DF8_POLY_OFFSET_NEG_NUM_DB_BITS((char)-24);
+			break;
+		case PIPE_FORMAT_Z16_UNORM:
+			offset_units *= 4.0f;
+			pa_su_poly_offset_db_fmt_cntl =
+				S_028DF8_POLY_OFFSET_NEG_NUM_DB_BITS((char)-16);
+			break;
+		default:
+			pa_su_poly_offset_db_fmt_cntl =
+				S_028DF8_POLY_OFFSET_NEG_NUM_DB_BITS((char)-23) |
+				S_028DF8_POLY_OFFSET_DB_IS_FLOAT_FMT(1);
+		}
 	}
 
 	radeon_set_context_reg_seq(cs, R_028E00_PA_SU_POLY_OFFSET_FRONT_SCALE, 4);
@@ -492,6 +494,7 @@ static void *r600_create_rs_state(struct pipe_context *ctx,
 	rs->offset_units = state->offset_units;
 	rs->offset_scale = state->offset_scale * 16.0f;
 	rs->offset_enable = state->offset_point || state->offset_line || state->offset_tri;
+	rs->offset_units_unscaled = state->offset_units_unscaled;
 
 	if (state->point_size_per_vertex) {
 		psize_min = util_get_min_point_size(state);