On Tue, Oct 15, 2013 at 3:28 PM, Kenneth Graunke <kenn...@whitecape.org> wrote:
> On 10/14/2013 10:12 AM, Anuj Phogat wrote:
>> Implement the FS backend for new builtins added by the extension:
>> in vec2 gl_SamplePosition
>> in int gl_SampleID
>> in int gl_NumSamples
>> out int gl_SampleMask[]
>>
>> Signed-off-by: Anuj Phogat <anuj.pho...@gmail.com>
>> ---
>> src/mesa/drivers/dri/i965/brw_fs.cpp | 109
>> +++++++++++++++++++++++++++
>> src/mesa/drivers/dri/i965/brw_fs.h | 4 +
>> src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 23 ++++++
>> src/mesa/drivers/dri/i965/brw_wm.h | 1 +
>> 4 files changed, 137 insertions(+)
>>
>> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
>> b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> index e5d6e4b..e4f7745 100644
>> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> @@ -1115,6 +1115,109 @@
>> fs_visitor::emit_frontfacing_interpolation(ir_variable *ir)
>> return reg;
>> }
>>
>> +void
>> +fs_visitor::compute_sample_position(fs_reg dst, fs_reg int_sample_pos)
>> +{
>> + int num_samples = ctx->DrawBuffer->Visual.samples;
>> + assert(num_samples >= 0 && num_samples <= 8);
>> +
>> + /* From arb_sample_shading specification:
>> + * "When rendering to a non-multisample buffer, or if multisample
>> + * rasterization is disabled, gl_SamplePosition will always be
>> + * (0.5, 0.5).
>> + */
>> + if (!ctx->Multisample.Enabled || num_samples == 0) {
>> + emit(BRW_OPCODE_MOV, dst, fs_reg(0.5f));
>> + }
>> + else {
>> + /* For num_samples = {4, 8} */
>> + emit(BRW_OPCODE_MOV, dst, int_sample_pos);
>> + emit(BRW_OPCODE_MUL, dst, dst, fs_reg(1 / 16.0f));
>> + }
>> +}
>
>> +fs_reg *
>> +fs_visitor::emit_sampleid_interpolation(ir_variable *ir)
>> +{
>> + assert(brw->gen >= 6);
>> + bool multisampled_fbo = ctx->DrawBuffer->Visual.samples > 1;
>> +
>> + this->current_annotation = "compute sample id";
>> + fs_reg *reg = new(this->mem_ctx) fs_reg(this, ir->type);
>> +
>> + if (multisampled_fbo && ctx->Multisample.Enabled) {
>
> One more thing. These two blocks have different conditions. For
> gl_SamplePosition, num_samples == 1 hits the MSAA case. For
> gl_SampleId, num_samples == 1 hits the non-MSAA case.
>
> I don't know which is right, but they should match.
we use num_samples > 1 to identify a multisample_fbo. I'll make
changes in gl_SamplePosition to match gl_SampleId.
Thanks
Anuj
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