On 07.07.2017 18:19, Juan A. Suarez Romero wrote:
When we have an interface block like:
layout (xfb_buffer = 0, xfb_offset = 0) out Block {
vec4 var1;
layout (xfb_stride = 48) vec4 var2;
vec4 var3;
};
According to ARB_enhanced_layouts spec:
"The *xfb_stride* qualifier specifies how many bytes are consumed by
each captured vertex. It applies to the transform feedback buffer
for that declaration, whether it is inherited or explicitly
declared. It can be applied to variables, blocks, block members, or
just the qualifier out. [ ...] While *xfb_stride* can be declared
multiple times for the same buffer, it is a compile-time or
link-time error to have different values specified for the stride
for the same buffer."
This means xfb_stride actually applies to the buffer, and not to the
individual components.
In the above example, it means that var2 consumes 16 bytes, and var3 is
at offset 32.
This has been confirmed also by John Kessenich, the main contact for the
ARB_enhanced_layouts specs, and also because this commit fixes:
GL45.enhanced_layouts.xfb_block_member_stride
This commit is in practice a revert of 598790e8564 (glsl: apply
xfb_stride to implicit offsets for ifc block members).
Thanks for taking care of this.
Reviewed-by: Nicolai Hähnle <nicolai.haeh...@amd.com>
---
src/compiler/glsl/ast_to_hir.cpp | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index c338ad7..3968657 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -7372,14 +7372,13 @@ ast_process_struct_or_iface_block_members(exec_list
*instructions,
qual->offset, &xfb_offset)) {
fields[i].offset = xfb_offset;
block_xfb_offset = fields[i].offset +
- MAX2(xfb_stride, (int) (4 * field_type->component_slots()));
+ 4 * field_type->component_slots();
}
} else {
if (layout && layout->flags.q.explicit_xfb_offset) {
unsigned align = field_type->is_64bit() ? 8 : 4;
fields[i].offset = glsl_align(block_xfb_offset, align);
- block_xfb_offset +=
- MAX2(xfb_stride, (int) (4 * field_type->component_slots()));
+ block_xfb_offset += 4 * field_type->component_slots();
}
}
--
Lerne, wie die Welt wirklich ist,
Aber vergiss niemals, wie sie sein sollte.
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