VDR: Fix vertex offset in indirect draw calls

[panos-lunarg]

No description provided.

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[hongSARC]

should the vertex offset not be stored along in index_count_first_index_pairs (well, not as pair, but as struct or tuple)?
Would be much shorter and not need this min/max computation and be more precise.

[hongSARC]

So if I understood what the code is doing correctly, in FindMinMaxVertexIndices function, you are processing the index buffer to find the minimum and maximum indices used in the range of the index data.
This function takes into account the index count and the first index, and computes the min and max of the indices.

Then, you are adding the vertex offset to the min and max values for the index range.

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When you add different offsets to the min and max, you essentially expand the range incorrectly, as you are applying two different offsets. You should be applying a single vertex offset to both the min and max values.

The offsets you add should be uniform for both min and max, based on the range of indices you are processing.

I think it should calculate the min and max indices first then apply the vertex offset for that specific draw call to the indices. Then track the overall min and max indices across all draw calls comparing the adjusted values.

[panos-lunarg]

So if I understood what the code is doing correctly, in FindMinMaxVertexIndices function, you are processing the index buffer to find the minimum and maximum indices used in the range of the index data. This function takes into account the index count and the first index, and computes the min and max of the indices.

Correct.

Then, you are adding the vertex offset to the min and max values for the index range.

When you add different offsets to the min and max, you essentially expand the range incorrectly, as you are applying two different offsets. You should be applying a single vertex offset to both the min and max values.

The offsets you add should be uniform for both min and max, based on the range of indices you are processing.

I think it should calculate the min and max indices first then apply the vertex offset for that specific draw call to the indices. Then track the overall min and max indices across all draw calls comparing the adjusted values.

I think I understand what you mean and I think you are right. I updated the patch accordingly

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[hongSARC]

Could you also pass the original binary file offset? (bufferOffset)

The vertexOffset is relative to the buffer segment for that draw, but the actual data in binary file may be in different location.
I'll need that bufferOffset to correctly subtract or add it when reading vertex data, ensuring that the offsets match the actual memory layout. Then I can properly adjust the vertex positions when parsing.

[panos-lunarg]

Could you also pass the original binary file offset? (bufferOffset)

What do you mean with bufferOffset? Do you mean the offsets used in vkCmdBindVertexBuffers, vkCmdBindIndexBuffer and co?

[hongSARC]

No, I'm looking for the absolute offset within the original binary file where the vertex buffer data starts. (I just referred as "bufferOffset")
This would allow me to correctly calculate the memory layout and adjust the vertex positions when parsing. The vertexOffset provided is relative to the buffer segment, but I need to know the starting point within the binary file to properly read the data.
Otherwise, I'll need to reconstruct it using buffer bindings (I think), which is more complex..

Maybe within the "parameters" or inside "vertexBuffers in api json? (fileOffset is what I meant. We need to have for both index buffer and vertex buffer file offset to handle indirect draw calls since it contains multiple draws I need to parse.)
example)

"indexBuffer": {
  "bufferId": 2145,
  "file": "indirect_indexBuffer_qs_2167_bcb_2094_dc_2103_uint16.bin",
  "fileOffset": 4
},
"vertexBuffers": [
  {
    "bufferId": 2144,
    "vertexBufferBinding": 0,
    "file": "indirect_vertexBuffers_qs_2167_bcb_2094_dc_2103_binding_0.bin",
    "fileOffset": 20
  },

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Here are the steps of my parsing, (FYI)
-Use firstIndex and indexCount to get the indices array from the index buffer.
-Use the vertexOffset (relative to the buffer segment) along with the "bufferOffset" (absolute offset within the binary file) to calculate the correct starting point for the vertex buffer.
With the correct starting point, I can then parse the vertex buffer using the calculated offset.