On 05/22/2012 09:07 AM, [email protected] wrote:
From: José Fonseca<[email protected]>
This is a long standing problem, that recently surfaced with the change
to enable perspective correct color interpolation.
A fix for all possible formats is left to the future.
---
src/gallium/drivers/llvmpipe/lp_bld_alpha.c | 31 +++++++++++++++++++++++++++
src/gallium/drivers/llvmpipe/lp_bld_alpha.h | 2 ++
src/gallium/drivers/llvmpipe/lp_state_fs.c | 5 ++++-
3 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/src/gallium/drivers/llvmpipe/lp_bld_alpha.c
b/src/gallium/drivers/llvmpipe/lp_bld_alpha.c
index 518969c..bf4e8c4 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_alpha.c
+++ b/src/gallium/drivers/llvmpipe/lp_bld_alpha.c
@@ -32,9 +32,12 @@
*/
#include "pipe/p_state.h"
+#include "util/u_format.h"
#include "gallivm/lp_bld_type.h"
#include "gallivm/lp_bld_const.h"
+#include "gallivm/lp_bld_arit.h"
+#include "gallivm/lp_bld_conv.h"
#include "gallivm/lp_bld_logic.h"
#include "gallivm/lp_bld_flow.h"
#include "gallivm/lp_bld_debug.h"
@@ -46,6 +49,7 @@ void
lp_build_alpha_test(struct gallivm_state *gallivm,
unsigned func,
struct lp_type type,
+ const struct util_format_description *cbuf_format_desc,
struct lp_build_mask_context *mask,
LLVMValueRef alpha,
LLVMValueRef ref,
@@ -56,6 +60,33 @@ lp_build_alpha_test(struct gallivm_state *gallivm,
lp_build_context_init(&bld, gallivm, type);
+ /*
+ * Alpha testing needs to be done in the color buffer precision.
+ *
+ * TODO: Ideally, instead of duplicating the color conversion code, we
would do
+ * alpha testing after converting the output colors, but that's not very
+ * convenient, because it needs to be done before depth testing. Hopefully
+ * LLVM will detect and remove the duplicate expression.
+ *
+ * FIXME: This should be generalized to formats other than rgba8 variants.
+ * It is, however, difficult to come up with a truly generic rule that would
+ * work for an arbitrary format. For example, how many bits should we use
+ * when doing alpha testing for B5G5R5X1_UNORM?
> + */
The GL spec addresses this in section 2.14.9 on page 71 of the 2.1 spec:
"""
For an RGBA color, each color component (which lies in [0, 1]) is
converted (by rounding to nearest) to a fixed-point value with m bits.
[...]
m must be at least as large as the number of bits in the corresponding
component of the framebuffer. m must be at least 2 for A if the
framebuffer does not contain an A component, or if there is only 1 bit
of A in the framebuffer.
"""
+ if (type.floating&&
+ util_format_is_rgba8_variant(cbuf_format_desc)) {
+ const unsigned dst_width = 8;
+
+ alpha = lp_build_clamp(&bld, alpha, bld.zero, bld.one);
+ ref = lp_build_clamp(&bld, ref, bld.zero, bld.one);
+
+ alpha = lp_build_clamped_float_to_unsigned_norm(gallivm, type,
dst_width, alpha);
+ ref = lp_build_clamped_float_to_unsigned_norm(gallivm, type,
dst_width, ref);
+
+ type.floating = 0;
+ lp_build_context_init(&bld, gallivm, type);
+ }
+
test = lp_build_cmp(&bld, func, alpha, ref);
lp_build_name(test, "alpha_mask");
diff --git a/src/gallium/drivers/llvmpipe/lp_bld_alpha.h
b/src/gallium/drivers/llvmpipe/lp_bld_alpha.h
index 06206a2..15f1284 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_alpha.h
+++ b/src/gallium/drivers/llvmpipe/lp_bld_alpha.h
@@ -39,6 +39,7 @@
#include "gallivm/lp_bld.h"
struct pipe_alpha_state;
+struct util_format_description;
struct gallivm_state;
struct lp_type;
struct lp_build_mask_context;
@@ -48,6 +49,7 @@ void
lp_build_alpha_test(struct gallivm_state *gallivm,
unsigned func,
struct lp_type type,
+ const struct util_format_description *cbuf_format_desc,
struct lp_build_mask_context *mask,
LLVMValueRef alpha,
LLVMValueRef ref,
diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c
b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index 11a3871..0bdc17f 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -345,13 +345,16 @@ generate_fs(struct gallivm_state *gallivm,
0);
if (color0 != -1&& outputs[color0][3]) {
+ const struct util_format_description *cbuf_format_desc;
LLVMValueRef alpha = LLVMBuildLoad(builder, outputs[color0][3],
"alpha");
LLVMValueRef alpha_ref_value;
alpha_ref_value = lp_jit_context_alpha_ref_value(gallivm,
context_ptr);
alpha_ref_value = lp_build_broadcast(gallivm, vec_type,
alpha_ref_value);
- lp_build_alpha_test(gallivm, key->alpha.func, type,
+ cbuf_format_desc = util_format_description(key->cbuf_format[0]);
+
+ lp_build_alpha_test(gallivm, key->alpha.func, type, cbuf_format_desc,
&mask, alpha, alpha_ref_value,
(depth_mode& LATE_DEPTH_TEST) != 0);
}
Reviewed-by: Brian Paul <[email protected]>
_______________________________________________
mesa-dev mailing list
[email protected]
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
